Development of Conductive Hydrogel-Based Anode Materials for Lithium-Ion Batteries

Development of Conductive Hydrogel-Based Anode Materials for Lithium-Ion Batteries | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Systematic Review Development of Conductive Hydrogel-Based Anode Materials for Lithium-Ion Batteries Wondwossen Melaku Yimer This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5548724/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The development of rechargeable lithium-ion batteries with high-strength density and long-cycle lifestyles is essential to address the growing demand for dense storage in various technology applications, including portable electronics, hybrid and electric vehicles, and power system. grid-scale energy storage. All of these must be sustainable electrochemically and generally robust. The main limitation in recognizing these functions is the lack of electrodes with excellent mechanical and electrochemical properties. CHs combine the electrical conductive properties of metals or semiconductors with the unique properties of hydrogels and are important for forming and assembling lithium ion battery electrodes. Which can contain a large amount of electrolyte solution in the conductive network of 3D nanostructures, providing a large number of sites on the surface for the required electrochemical reactions. Until now, 3D nanostructured CH has shown excellent performance when used as an electrode materials for LIBs. Future efforts are based on improving the intentional CH with controllable size, composition, shape, and interface. In this review, we focus on fabrication of CH, how conductive hydrogels are incorporated into the active materials (Si nanparticles, tin-metal alloy and transition metal oxides) of LIBs, and show some of the hydrogel electrode materials in LIBs based on Si, tin alloys and transition metal oxides based hydrogels. Electrochemistry Conductive Hydrogel Transitional Metal Oxide Tin alloy Carbon materials Silicon Anode Materials Lithium-Ion Batteries Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction With increasing attention to the fossil fuel burgeoning burden, energy disasters and environmental issues, finding a source of sustainable and stable intensity has become the world's top priority. Although various renewable energy sources have been explored and applied to many components of daily activities, including wind energy, geothermal energy, tidal energy, and solar energy, due to the significant fluctuations and unpredictability of climate and environment, seldom widely used. [ 1 ]. It is essential to propose efficient energy storage structures, which provide energy to protect the grid when necessary and maintain energy production when there is a surplus of energy production [ 2 ]. Therefore, due to the unexpected increase in global energy consumption, the demand for energy storage and conversion equipment is gradually increasing [ 3 ]. Compared to ordinary storage devices (e.g. as lead-acid batteries, nickel metal hydroxide batteries etc.), rechargeable lithium-ion batteries (LIBs) are the most promising candidates in a series of electric power applications. Because they have the following advantages: extremely high working voltage, high energy density and long life cycle [ 4 ]. In addition to improving the performance of LIBs, the massive efforts of various academic circles and companies remain committed to realizing large-scale energy storage in fully electric vehicles, military and aerospace applications [ 5 ]. Since the overall electrochemical performance of LIBs is closely related to the performance of the electrodes, the choice of electrode materials is extremely important. The negative electrode plays an indispensable role in LIBs, because the characteristics of the negative electrode directly affect the electrochemical performance of the battery. The physical and chemical properties of the active material of the anode determine the behavior of the battery, so it must be considered and managed properly. Some notable characteristics of raw materials certainly provide convenience for your software as active negative electrode materials, but the inherent defects of the materials limit their optimal use. Therefore, in addition to material selection and preparation, excellent modifications and architectural drawings are also essential for increased battery performance [ 6 ]. Carbon-based materials (e.g., graphite) are generally used as anode substances for LIBs due to the fact of their low cost, high abundance and notable kinetics [ 7 ]. However, the low operating voltage of graphite, which is close to the voltage of lithium electroplating, can cause protection problems. Its limited theoretical capacity of 372 mAhg − 1 prompts researchers to search for safer and more potential negative electrode candidates. [ 8 ]. To improve the capability of anode materials, full-size interest has been dedicated to alloy-type anode materials, owing to their high precise capacity and safety characteristics [ 9 ]. Among different alloy types of anode materials, silicon (Si) and tin (Sn) are considered promising alternative materials for the next generation of LIB. Si and Sn have theoretical capacities of 4200 mAhg − 1 and 994 mAhg − 1 , respectively. They are completely lithiated to the Li 22 Si 5 and Li 22 Sn 5 phases, based entirely on the alloying reaction between the respective elements and lithium, which is related to the intercalation mechanism of graphite. [ 9 ][ 10 ]. Furthermore, because silicon has huge exploitable reserves, it can be explored and manufactured at a lower cost. However, before practical application, two major challenges of silicon anodes must be solved. [ 4 ]. Other anode materials which are applicable in lithium ion battery are transition metal oxides(TMOs). TMOs (M x O y , M = Fe, Co, Ni, Mn, Mo, Cr, Nb, etc.) are attractive candidates because they can provide about 2–3 times higher reversibility than traditional graphite Capacity. And eco-friendliness, corrosion resistance and decent cost financial system.[ 11 ]. However, these anode materials endure a large extent variant throughout cycling, main to poor electrochemical performance[ 9 ], and due to the large number of extension exchanges and kinetic and thermodynamic constraints throughout the cycle, they usually exhibit low initial Coulombic efficiency, negative charge capacity, and rapid decay potential.[ 1 ]. In the final few decades, exceptional effort has been made to conquer the boundaries of Si, Sn and TMOs as anode materials for LIBs using electrical conducting hydrogels (CHs). CH is considered a viable platform for delineating and assembling lithium-ion batteries and other energy storage supplies [ 12 ]. Due to reality, this "water-based soft material" synergizes the advantages of hydrogels and electronic conductors, and has high conductivity and mechanical flexibility. It is more suitable for electron and ion transport, as well as for the first-class interface interaction between solid phase and response phase[ 13 ]. This review is devoted to the conductivity of hydrogels, manufacturing methods and their applications in LIB anode materials. The modification aspect of hydrogel in depth, by adding carbon-based materials and conductive polymers to make it conductive. The conductive material can be physically or chemically bonded to the hydrogel matrix. The conductivity is affected by the size of the nanoparticles, the presence of hydrogel-bound water, and the presence of any other components that may affect the conductivity. The review will focus on the application of these conductive hydrogels in lithium-ion battery anode materials. 2. Electrically Conductive Hydrogels Hydrogel is a cross-linked polymer network that is elastic and packed with a lot of fluid [ 14 ] or it is a gel that can contain a required amount of water and swell to a certain degree of balance ( equilibrium extent) in three dimensional (3D) network since it is made up of the terms "hydro" (water) and "gel"[ 15 ]. The hydrophilic component is answerable for expanding and putting away a lot of water. ECHs are a rising gloriousness of hydrogels joining a hydrophilic framework with electrical conducting fillers, which incorporate metal nanoparticles, conducting polymers and carbon-based substanes [ 14 ][ 16 ]. As a result of reversible functionality between swelling and de-swelling, electrical conducting hydrogels (ECHs) can also be designed to have dramatic liquid alternation, quantity or volume changes, and to give a controllable response to different environmental conditions, including ion and light conductivity, electrical or magnetic area. [ 17 ]. In general, electrical conducting hydrogels (ECHs) have huge promises in different packages in renewable electricity, [ 18 ][ 19 ], and environmental engineering [ 20 ] to medical devices[ 21 ][ 22 ] and drug delivery structures[ 23 ][ 24 ]. 2.1 Conducting Polymer based Hydrogels Conductive polymers (CPs), which include poly(acetylene, aniline, pyrrole, thiophene, (phenylene vinylene), etc.)[ 25 ], are similar to metals and semiconductors in that they have electrical and optical properties while maintaining the properties of ordinary polymers. It has the characteristics of a cheap, simple and flexible synthesis method. [ 26 ]. They are versatile in that their properties can be easily adjusted by surface functionalization and /or doping. [ 27 ]. The basic performance of charge propagation in CPs is mainly based on the following two mechanisms: (i) the transfer of delocalized electrons through conjugated systems such as polypyrrole (PPy) and PANI) etc., and (ii) the transfer of electrons via the mobile electron exchanges and reacts between adjacent redox sites in the redox polymer [ 24 ] (electron jumping). Conductive CP makes it an important category of materials, with wide applications [ 28 ], mainly used for energy storage[ 29 ][ 30 ][ 31 ], electrochromic screens [ 32 ], electrocatalysis and photocatalysis [ 33 ], and sensors [ 34 ], [ 35 ], [ 36 ], etc. Conductive hydrogel is the name used to define the hybrid network formed by the combination of cross-linked hydrogel and CP. They have similar properties to traditional hydrogels, but have the additional advantage of electrical conductivity. [ 37 ]. CPH is a material that generally contains CP together with a carrier polymer. Due to its special structure, CPH has some interesting characteristics, such as: high water content, softness, plasticity and mechanical integrity, porosity and high surface specificity.[ 38 ]. In addition, they are characterized by mixed electronic and ionic conductivity, redox activity, and conversion between conductive and insulating forms in CPs. Mostly used conductive components in CPHs are PANI, PPy and PEDOT [ 38 ][ 39 ][ 40 ][ 41 ][ 42 ]. The most studied synthetic method for forming CP hydrogels is to polymerize CP using a hydrogel matrix that has already been manufactured. [ 43 ]. Generally, the following manufacturing routes have been studied to develop CPHs. The first is to gel the CPs and the hydrophilic polymer/ monomer mixture by self-assembly or by introducing cross-linkable elements. In this case, the conductivity of this hydrogel can usually be improved by increasing content of the conductive polymer. The organogel conductor was synthesized by this method. [ 42 ]. Lee et al. Synthesized organogel PEDOT: PSS/Acrylamide [ 44 ], which is composed of poly (3,4 ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), polyacrylamide (PAAm) and glycol solvent. The detailed synthesis process is shown in Fig. 1 a. PEDOT: PSS provides a conductive pathway for the organogel to transmit electrical signals and PAAm, because the cross-linked polymer network makes it highly flexible and stretchable. Another method is to grow CP on a precast hydrogel by chemical oxidation and electrochemical polymerization. The conductivity of CPHs can be used for different purposes in a wide range by controlling the amount of polymerization of CPs. In this way, Li et al. synthesized PANI PVA hybrid conductive hydrogel through dynamic borate bonding.[ 45 ]. PVA act as a soft polymer and makes the hybrid hydrogels have excellent mechanical properties, while PANI act as a rigid polymer and provides enhanced electrical properties and stability. PANI can be cross-linked with PVA through the boronic acid group in PANI to form a strong CH with the mesoporous structure indicated in Fig. 1 b. Furthermore, electrochemical polymerization can also be used to develop CPs in prefabricated hydrogels[ 50 ][ 51 ]. ECHs manufacturer inspired by this work from many hydrogels (PAM, PAA, PVA, agarose, and chitosan) and many CPs (polypyrrole, polyaniline, and polyethylene dioxythiophene)[ 17 ][ 21 ][ 52 ]. In a study published by Ambrosio et al., [ 21 ], the aniline monomer was first dissolved in a polyethylene glycol diacrylate (PEGDA) solution; then UV polymerization was carried out to build a cross-linked hydrogel with a super-porous structure network. Another ECH fabricated was PANI/heparin-methacrylate hydrogel, its synthetic method is shown in Fig. 1 c [ 46 ]. First, the bio-based heparin hydrogel network is formed by UV curing; then it is immersed in the aniline solution to diffuse the monomer into the porous structure. Finally, PANI/heparin methacrylate hydrogel is formed by the oxidative polymerization of aniline, and PANI is physically embedded in the heparin methacrylate hydrogel matrix. Yeen and others [ 53 ] used polyaniline (PANI) and polyacrylamide (PAA) to prepare a conductive hydrogel. PANI/PAA hydrogel is prepared by the interfacial polymerization method. Various characterization tests were performed in order to study the properties of CHs, such as FTIR, conductivity test, swelling test, and compression test. The results were compared with non-conductive PAA hydrogels. The incorporation of PANI into PAA hydrogel significantly improves the conductivity of the hydrogel. Compared with PAA hydrogel, the swelling rate of PANI/PAA hydrogel is reduced, and Young's modulus is increased. The third method involves the use of doped molecules to crosslink CP chains through multiple functional groups to produce several CPHs that do not contain insulating components [ 47 ][ 48 ]. Among them, Bao et al., they first described phytic acid to form PANI hydrogels [ 47 ]. The gel formation mechanism of PANI hydrogel is shown in Fig. 1 d. This type of CPH has high conductivity because it avoids the use of insulating components and builds a 3D conductive polymer network, which promotes electron transport and ion diffusion. In addition to phytic acid, copper phthalocyanine-3’, 4’, 4’’, 4’’’,-tetrasulfonic acid tetrasodium salt can be used to form polypyrrole hydrogel by crosslinking polypyrrole chains[ 48 ]. The interfacial polymerization strategy was used to prepare nanostructured conductive PPy hydrogels at the organic/water two-phase interface as reported by Yu et al . [ 48 ]. CuPcTs and PPy are connected to each other and form a PPy fiber, which crosslinks into a hydrogel. Dopants CuPcTs are used as gelling agents to self-assemble 1D PPy nanofibers "collar-shaped" into a 3D hydrogel networks via electrostatic interaction and H-bonding as indicated in Fig. 1 e. Chen et al., synthesized a hydrogel by integrating two types of conductive polymers PANI and PEDOT using phytic acid as the molecular bridge[ 49 ]. Some of PSS replaced by the acid and promotes the conversion of the PEDOT chain from the benzoic acid structure to the quinone structure. The resulting hydrogel is composed of a 3D network of PEDOT sheets embedded with PANI; due to the molecular interaction between PANI and PEDOT. Compared to PEDOT hydrogels, it has greatly improved mechanical properties. Since each phytic acid molecule has six phosphate groups, it can interact easily with the PEDOT and PANI chains. Phytic acid used as a molecular bridge and cross-link PANI and PEDOT at the molecular level in order to form a PEDOT/PANI hydrogel. The gel mechanism is shown in Fig. 1 g (i). During the gelling process, it produces an independent PEDOT/PANI hydrogel of high mechanical strength. The independent PEDOT/ PANI hydrogel is composed of a 3D network of PEDOT sheets; PANI particles appear to be embedded in each foil, promoting rapid transmission of electrons and ions, resulting in high capacitance performance. Each paper features a rough surface (Fig. 1 g(ii)) rather than the smooth surface of separate PEDOT or PANI hydrogel, meaning that PANI is successfully integrated into PEDOT. 2.2 Carbon material-based hydrogels Carbon materials, such as carbon nanotubes (CNT), graphene, activated carbon, carbon fibers, carbon dots, and porous carbon, are considered conductive due to their unique high conductivity, excellent environmental stability. and low cost production and promising conductor material for hydrogel [ 54 ][ 55 ][ 56 ]. From various carbon materials, carbon nanotubes and graphene have been extensively explored in materials science, and is used as conductive fillers in conductive hydrogels for flexible and portable electronics products. Due to its electrical, thermal and mechanical properties, it has played an important role in a wide range of research fields. Their improved electrical properties are very attractive, suggesting that they can be used as reinforcing materials and additives for composites [ 57 ]. Self-assembly of mixed and modified with various polymers, the two most common methods for preparing conductive carbon-based hydrogels. Some carbon-based hydrogels are discussed below. The conjugated structure graphene cannot be uniformly dispersed in water, which limits its application in the manufacture of conductive hydrogels. Modified hydrophilic polymer is an effective way to promote good dispersion of graphene in H 2 O. Polydopamine (PDA) can cover almost all nanomaterials, so nanomaterials have a good dispersion in the hydrogel network. On this basis, Han's team designed a partially reduced graphene oxide (pGO) PAAm hybrid hydrogel with conductive PDA[ 58 ]. Figure 2 a illustrates synthesis process to form a hydrogel. First, GO is dissolved and reduced partially in the PDA solution, and obtained by polymerizing dopamine under oxidizing and alkaline conditions. Then, CHs were developed by polymerizing acrylamide monomers in the presence of rGO. The fully reduced GO (rGO) can be uniformly dispersed in the PAAm hydrogel lattice and act as an electronic pathway, so that the conductive hydrogel has good conductivity. GO which is not reduced by oxygen-containing groups can interact with the PAAm chain through H-bonding and electrostatic interaction. PDA also interacts with the PAAm chain through π-π stacking and H-bonding. These synergistic effects of non-covalent interactions give the CHs toughness and high stretchability. Self-assembled graphene hydrogel with a cross-linked three-dimensional porous structure synthesized by Shi et al., (Fig. 2 b1)[ 59 ]. The uniform suspension of GO sealed in an autoclave and kept at 180 ° C. After heating for 12 hours without any interference, and then the autoclave is cooled to room temperature and the graphene hydrogels are formed through supramolecular interactions such as H-bonding, electrostatic interaction, and π-stacking (Fig. 2 b2). The characterstics of graphene hydrogels highly dependent on the GO concentration during the process. As the amount of GO is low, only black powder is formed. And increasing the amount of GO, a well-defined graphene hydrogel can be formed (Fig. 2 b3). hydrazine or hydroiodic acid used to further treat the dispersed graphene hydrogel to remove residual oxygen containing functional groups and improve conductivity. This study provides a method to construct three dimensional (3D) hydrogel networks from 2D graphene sheets, which has inspired a number of new designs of graphene-based hydrogel networked systems. The graphene hydrogels obtained by this method exhibit a clear networked structure with high mechanical strength (Fig. 2 b(4)), but if they do not contain a hydrophilic polymer matrix and therefore lack the ability to retain a large amount of liquid . Another type of rGO-based hydrogel is synthesized by encapsulating it in PEGDA hydrogel (CTS-g-GMA). First, the CTS was modified by GMA grafting to obtain the photo-crosslinkable group in its skeleton (methacrylation degree: 7%). Then, rGO is encapsulated in PEGDA hydrogel (CTS-g-GMA) to make conductive hydrogel, because rGO has the advantages of low preparation cost, two-dimensional planar structure, large specific surface area, and dispersibility in many organic solvents and water. Due to its reactive side groups (OH and COOH), rGO molecules interact with the polymer network formed by the photopolymerization process between CTS-g-GMA and PEGDA, as shown in Fig. 2 c. In order to create a chemical cross-linking network, GMA graft-modified CTS was used as the main component, and PEGDA was used as a cross-linking agent due to its acrylate group. A PEGDA hydrogel without rGO (CTS-g-GMA) was also synthesized to predict effect of rGO on the physico-chemical characterstics of the hydrogels. [ 60 ]. Li et al. [ 61 ] proposed a strategy to make a strong, self-healing and conductive hydrogel containing rGO. The grafted polyacrylic acid GO (GO-g-PAA) fabricated incorporated it into a chemically cross-linked PAM network to get GO-g-PAA/PAM hydrogel, which is subsequently treated with ascorbic acid solution at room temperature and passed rGO-g-PAA/PAM to obtain a hydrogel. The reversible H-bond between the grafted PAA chain and the PAM matrix increase the interfacial interaction between GO/rGO and the hydrogel matrix. Therefore, both GO-g-PAA/PAM and rGO-g-PAA/PAM hydrogels have improved tensile properties, excellent energy dissipation, and rapid self-recovery. In situ chemical reduction of GO-g-PAA in the hydrogel matrix causes the rGO-g-PAA/PAM hydrogels to have good electrical conductivity and significant changes in tensile strength. Figure 2 d shows a schematic diagram of the synthesis of GO-g-PAA/PAM and rGO-g-PAA/ PAM hydrogels. At the begning, GO-g-PAA is synthesized from GO, dispersed in water, and neutralized with NaOH to form a long-term stable aqueous solution. Next, use MBA as a chemical crosslinking agent in GO-g-PAA aqueous solution to perform AM in situ polymerization to obtain GO-g-PAA/PAM hydrogels. Finally, ascorbic acid was used as a reducing agent to perform a mild in situ chemical reduction of GO-g-PAA in the hydrogel matrix [ 63 ] inorder to obtain rGO-g-PAA/ PAM hydrogels. The GO-g-PAA/PAM hydrogels observed to be brown with the naked eye. The rGO-g-PAA/PAM hydrogel is black, indicating a decrease in GO-g-PAA. GO-g-PAA and rGO-g-PAA not only act as nanofillers, but also act as multifunctional physical crosslinkers in the hydrogels by grafting the H-bonds between the PAA chains and the PAM matrix. [ 64 ]. The reversible hydrogen bond between the grafted PAA chain and the PAM matrix improves the interfacial interaction between GO/rGO and the hydrogel matrix. Due to improved interface compatibility and effective energy dissipation, GO-g-PAA/ PAM and rGO-g-PAA/PAM hydrogels exhibit improved tensile mechanical properties and exhibit good self-healing capabilities, and exhibits satisfactory conductivity. The combination of these properties, make rGO-g-PAA/PAM hydrogels more widely used in different applications. Apart from graphene, CNTs have widely incorporate into hydrogel networks due to their tube like structures and highest electrical properties. As described in Fig. 2 e, gelatin methacrylate hydrogel (GelMA) incorporating CNTs is prepared by in-situ polymerization through ultraviolet radiation [ 62 ]. The uniform inclusion of CNTs in the hybrid hydrogel can be attributed to the uniform dispersion of the GelMA-coated CNTs in the prepolymer solution. Uniform crosslinking of GelMA coated CNTs through acrylic groups results in a network structure. 3. Conducting Hydrogels Used in Lithium-Ion Battery Over the years, researchers have designed hydrogels in various ways to meet the considerable requirements of LIB electrodes [ 4 ][ 65 ] [ 66 ][ 67 ][ 68 ][ 69 ]. The following table lists the electrochemical characteristics of some ECH incorporated into the active electrode of LIBs and compared. The active anode materials are Si, tin metal alloy and transition metal oxides. ECH is currently used substances that specify LIB, and given their electrochemical and physical properties, the following dialogue will focus on intentional ECHs. 3.1 Silicon based Hydrogels For every one silicon atom, four lithium atoms can be bound to form Li 22 Si 5 [ 70 ], Si anode encounters problems inclusive of massive extent change (300–400%) after lithiation/delithiation cycles ensuing mechanical fracture, loss of interparticle electric contact and repeated side reactions with electrolytes, it has not yet been broadly commercialized [ 71 ]. Several improvements have been developed to increase the electrochemical performance of Si-based LIB anodes. Design Si nanostructures: Si nanocrystals [ 72 ] nanowires [ 73 ], core-shell nanofibers [ 74 ][ 75 ], nanosheets [ 76 ], nanotubes [ 77 ], nanospheres [ 78 ], Si nanoporous [ 72 ], Si/carbon nanocomposites [ 79 ], [ 80 ], Si NPs coated by graphene [ 81 ] [ 82 ][ 83 ], and applied polymer binders to Si nanoparticle electrodes such as PAA-P (HEA-co-DMA)[ 84 ], PAA-UPy [ 85 ], PAA-PBI [ 86 ], PD/PAA [ 87 ], CS-PAA [ 88 ], etc. However, since the electrode still suffers weak mechanical binding, nanoparticle agglomeration, poor network contact and pulverization during cycling because of large volume change during lithation/delithation[ 89 ], and applying the new class of polymeric materials are become known which are conductive polymer hydrogels. Hydrogels are 3D networks of crosslinked polymer chains that readily take in water and swell without dissolving [ 90 ]. They are highly flexible because of their high water content. The hydrogels are capable of providing high ionic conductivity, electronic conductivity [ 91 ], electrochemical activity [ 92 ], structural flexibility [ 14 ] and electrolyte permeability [ 93 ] to improve energy-storage device performance. Hydrogels from conductive polymeric materials have been explored for a broader range of applications, such as energy conversion and storage, sensors, actuators, medical and biological equipment, and superhydrophobic coatings. [ 94 ]. Some of Si based conductive polymer hydrogels anode materials which has been used for lithium ion battery are discussed below. Wu et al., synthesized ECH matrix Si/PANI hydrogel anode material by in situ polymerization [ 65 ].. Figure 3 a shows that each SiNP is encapsulated in a conductive polymer floor covering and similarly connected to a highly porous hydrogel framework. Through interaction between the surface OH groups and the phosphonic acid in the phytic acid molecule of the crosslinking agent (right column), or due to the electrostatic interaction between the negatively charged OH groups and the positive cost PANI due to the Phytic acid doping, the SiNP has been lined according to the polymer layer. The Si -PANI hydrogel is then covered with a modern copper foil current collector for electrochemical measurement. The CV experiment for both PANI and Si-PANI hydrogel was realized in a capacity window of 0.01-1 V at a scan rate of 0.1 mVs − 1 in half of the cells, instead of Li/Li + (Fig. 3 b). The results show that Si contributes to the capacity of the entire electrode in most areas. According to Fig. 3 c, at a modern density of 1.0 Ag − 1 , the well-known Si/PANI composite shows a constant capacity of 1600 mAhg − 1 after 1,000 cycles, which is much higher than the use of binders, silicon ordinary nano silica or the easy combination of SiNPs and PANI. The composite electrode has a perfect capacity at 2500 mAhg − 1 , the charge-discharge rate is between 0.3 Ag − 1 and 3 Ag − 1 and the high current / potential lithiation slope during charge and discharge is between 0.3 and 0.01 V 3.0 Ag − 1 . Figure 3 d and e shows that a composite electrode with a capacity of ~ 550 mAhg − 1 can maintain a capacity of 91% after 5000 cycles at a current density of 6 Ag − 1 , which confirms its better cycle stability. Yu et al., prepared a 3D Si/PPy/CNT ternary conductive hydrogel anode electrode [ 4 ], They reported on a new type of silicon anode, consisting of a porous, three-dimensional (3D) layered nanostructure with electrically conducting single-walled carbon and Si NPs composition in a polypyrrole (PPy) framework. Nanotubes (SWCNT) are used as electron enhancers, as shown in Fig. 4 a. The continuous PPy framework provides a unique porous structure to promot electron and ion transport adapt to the enormous volume changes of Si NPs. The SWCNTs used as the housing and electrical conductive structure further enhancing the integration of Si/CP structure and the electrical conductivity of the electrode, as shown in Fig. 4 b. EIS performed to check the lithiation/delithiation stability of the Si-PPy/CNT during the electrochemical process. The result of the Nyquist diagram (Fig. 4 c) of the hydrogel electrode shows no significant increase in impedance was detected after cycling, indicating that due to the unique hybrid electrode design and high efficiency in the cycling process, electron/ion transport through the porous electrode in 3D layers in between. The CV of the Si-PPy/CNT hydrogel electrode is shown in Fig. 4 d. A high redox peak near 0.2 V corresponds to the Si-Li alloy reaction, and two clear correlations are observed related to the delithiation of Si at 0.40.6 V. Redox peak. As the SiNPs that react with lithium are gradually activated, the size of all current peaks increases with increasing number of cycles in the first cycle and the addition of SWCNT to the Si-PPy binary electrode system increased chemical reversibility of the electrical energy of the ternary electrode. The first discharge capacity of the hydrogel electrode is 3600 mAhg − 1 , which is about 10 times that of the traditional graphite anode (372 mAhg − 1 ). It then stabilized at about 1600 mAhg − 1 in 1000 cycles. Within the potential window of 0.01 to 1 V, the capacity retention rate was 86% compared to Li/Li + (Fig. 4 e). Furthermore, the coulombic efficiency of the Si-PPy/CNT electrode was 78.2% in the first cycle and 99.5% in subsequent cycles (Fig. 4 f). Jiang et al., synthesized porous 3D Si/SiO x /GH conductive hydrogel successfully composited to fabricate LIBs anode materials [ 95 ]. These compounds are composed of self-assembled 3D Graphene (GH) networks in which embedded silicon NPs, are covered with an ultra-thin layer of SiOx. SEM image in Fig. 5 a shows that Si/SiO x NPs are uniformly dispersed in the GH structure. Despite the presence of the SiO x coating (as indicated by the arrow), other NPs are still aggregate in micron-sized clumps. However, as the thickness of the SiO x coating increases, the average size of the agglomerates decreases, and hence it improves the overall dispersion of the Si/SiO x NPs. It is worth noting that changing the weight load of Si/SiO x has little effect on the microstructure of the composite material. Therefore, an ultra-thin layer of SiO x is manufactured on the surface of the Si NPs in order to improve their dispersion in the matrix and hence improve their interfacial adhesion with graphene sheets. Figure 5 b shows that the Si/SiO x /GH composite constructed electrode shows excellent speed performance (1020 mAhg − 1 at 4 Ag − 1 ) with good cycle stability (1640 mAhg − 1 , at 10 and 140 at 0, 1 Ag − 1 ) Maintain 80 ° speed between cycles), where the Si/SiO x /C value of is considered favorable (520 mAhg − 1 to 4 Ag − 1 with 75% by weight of Si/SiO x ). In Fig. 5 c, a slight gradient appears in the range of 0.3 to 0.6 V, corresponding to the lithation of Si and delithation of Li x Si phase, respectively. This means that an increase in current density has almost influenced the shape of the curve. The CV profile of the composite electrode if SiO x /GH is shown in Fig. 5 d. In scanning of the anode, a peak was observed at 0.74 V, 0.01 V and 0.15 as the degradation of the electrolyte and the formation of the SEI film is shown. As lithation of Si and GH, indicates the formation of the SEI layer, and the formation of several phases of LiSi, respectively. In an anode price, two apparent peaks of 0.35 and 0.5 V showed disinposition of the LiSi alloy. Excellent electrochemical performance can be attributed to 3D opening and porous structures of GH openings and 3D porous structures that can be adapted to a large internal space and volume change of nanoparticles and highly porous 3D structures there. Oh, et al ., they reported [ 96 ] a 3D self-assembled Si/PANI-SGN porous nanocomposite electrodes, prepared by a low-cost, scalable, complete solution processing method, using aniline is a monomer to form a PANI, SGN as a 3D soft template and as an electrical enhancer in the presence of SiNPs, followed by oxidative polymerization in situ by ultrasonic treatment. Since SGN is interconnected with PANI, SGN forms a smooth porous structure. At the same time, when SiNPs was added to PANI-SGN nanocomposites with a small amount of PA, the SiNPs- PANI/SGN/PA compounds showed that PANI-SGN hydrogels embedded together to form porous nanostructures, as shown in Fig. 6 a.. Electrochemical performance is expressed as follows. As shown in Fig. 6 b, the CV measurement is performed on the potential window of 0.01-1.0 V with respect to Li/Li + at a scanning speed of 0.1 mVs − 1 in a half-cell. The peak observed at 0.19 V corresponds to the conversion of crystalline Si to the Li x Si phase, while the two peaks at 0.43 and 0.51 V correspond to amorphous (α) α-Li x Si delithiation to α-Si. The expanded peak potential separation between the anode peak and the cathode peak indicates that the electrochemical reversibility of the ternary electrode which is enhanced by adding SGN to the Si/PANI binary electrode system. Figure 8 c shows that the electrochemical performance of the Si/PANI/SGN composite electrode is significantly higher than that of the Si/PANI electrode under a deep charge-discharge cycle of 1 to 0.01 V, and maintains a stable capacity (red line, b) for a long period of time. The coulombic efficiency stabilizes around 100% in long cycles. Furthermore, these results indicate that by protonating the nitrogen group in PANI, SGN reacts with the aniline monomer and can be used as an excellent gelling agent, electrical conductor and reinforcing agent. Figure 6 d anode shows that the first cycle EC is ~ 78% (discharge capacity, 1.87 mAhcm − 2 charge capacity, 1.45 mAhcm − 2 ), and easily increases to 91% in the second cycle, and finally stabilizes above 99.5%. Then cycle at a rate of 0.33 mAcm − 2 . From the lowest current density to the highest, we found that the Si/PANI/SGN composite material holds the alloying and unlocking deck well. As shown in Fig. 8 e, the reversible lithium extraction capacity and excellent EC are found to be consistent with the robust performance of the electrode under high current density at a rate of 5.2 mAcm − 2 for up to 5000 charge-discharge cycles 3.2C. Compared to Si/PANI, the improved speed performance of the ternary anode Si/PANI/SGN further confirms the advantages of SGN as an electronic enhancer. These results also support that the conductive polymer SGN hydrogel structure provides a channel for rapid electron transmission, thus providing excellent speed capability. Ozkan et al., synthesized the rGO wrapped PPy/Si electrodes using a solution-based sol-gel polymerization process [ 97 ]. SEM micrograph shows the structure and morphology of the PPy/ Si/rGO compound in Fig. 7 a. Due to hydrogen bonding and electrostatic interactions between the ternary components: Si, pyrrole, and phytic acid in the precursor, the polymerized PPy hydrogel produces a uniform coating to encapsulate the Si. Before polymerization, the diameter of the Si ranged from 50 to 70 nm. A gel-like conductive layer was formed with a thickness of 10–20 nm to coat Si, which was confirmed by the increase in diameter of Si at 80–90 nm after polymerization, as shown in Fig. 9 b. The PPy coating helps maintain the integrity of the solid electrolyte interface (SEI) layer during the expansion process. The PPy gel also generates a continuous conductive frame to shorten the transmission length of electrons and ions while preventing the SINP from separating from the electrode. The rough surface has a 30–60 nm nanopore, which aids in the rapid diffusion of lithium ions, and the micropore reduces Si volume expansion during the lithiation process (Fig. 7 b). It is worth noting that the PPy/Si are wrapped in the rGO sheet or covered flat with rGO on the surface of Si. Therefore, rGO can improve the electrochemical stability of the network because its functional groups (such as carboxyl and hydroxyl) bind to the surface of PPy/Si. In addition, the excellent conductivity of rGO can promote the transfer of electrons and charges, thus improving the rate performance. Here, silicon NPs are coated with CHs and wrapped in rGO sheets through a simple solution-based sol-gel process. In-situ polymerized PPy hydrogel forms an interconnected 3D fiber matrix. The amine and OH groups of the hydrogel help to encapsulate Si through hydrogen bonding. Constant current charge, discharge and cycle performance are measured in the voltage range of 0.01 to 1 V (compared to Li + /Li). Figure 7 c shows the speed capability of the PPy/Si/rGO composite electrode up to 2.1 Ag − 1 , with up to 500 additional cycles at 2.1 Ag − 1 . The first cycle is performed at 0.1 Ag − 1 , followed by 9 cycles at 0.2 Ag − 1 and 10 cycles at 0.4 Ag − 1 . This process is necessary to fully activate Si while promoting the formation of stable SEI confirmed by the cycle. The first discharge capacity of the PPy/Si/rGO electrode is 3323 mAhg − 1 , the charge capacity is 2639 mAhg − 1 , and the corresponding coulombic efficiency is 79.4%. After being discharged at a high rate of 2.1 Ag − 1 , the PPy/Si/rGO electrode showed reversible capacities of 1312, 1285 and 1066 mAhg − 1 at 100, 250 and 500 cycles. The average Coulombic efficiency (> 99%) of the cycle at 2.1 A g1 indicates that the PPy/Si/rGO anode has good stability and reversibility. In contrast, PPy/Si without rGO sheets showed a capacity of 742 mAhg − 1 after 500 cycles at 2.1 Ag − 1 . Support for the addition of rGO greatly improved the stability and velocity performance of the electrode. Constant current charge/discharge curve. The excellent performance of the anode can be attributed to several factors including the interconnected layered PPy framework, the formed Ppy coating on the SiNPs, and the addition of rGO flakes as a conductive additive for the PPy/Si electrode. 3.2. Tin (Sn-M, M = Cu, Ni, Fe) alloys based hydrogels Due to the massive deposition of tin in nature and the high theoretical capacity of approximately 994 mAhg − 1 , tin-based materials are considered as promising anode alternatives [ 98 ][ 99 ]. However, the low capacity retention rate and rate capacity are usually attributed to the huge volume change during the Li + insertion and removal process, which not only leads to severe splashing of the current collector and subsequent power failure, but also leads to unstable SEI in Sn surface. [ 100 ]. To overcome such problems, several strategies has been developed: (i) Developing various nanostructures of Sn and Sn-based nanoscale materials: monodisperse Sn nano particles[ 101 ] Sn/SnO 2 nanoparticles [ 102 ], nanoporous Sn NPs [ 103 ][ 104 ], Sn, SnS, and SnO 2 nanocrystals[ 105 ], dispersing Sn nanoparticles in Carbon Matrix [ 106 ], Ultra-small Sn NPs embedded in nitrogen-containing porous carbon[ 107 ], nanostructured Sn/nitrogen-doped carbon composites (Sn/NCs) [ 98 ] etc., alloying of Sn with electrochemically inactive metals: amorphous Sn–Co–C composites [ 108 ], Fe–Sn [ 109 ][ 110 ][ 111 ][ 112 ], Co–Sn [ 113 ][ 114 ][ 115 ][ 116 ][ 117 ][ 118 ][ 119 ], Cu–Sn [ 120 ][ 121 ][ 122 ][ 123 ], Ni–Sn [ 124 ][ 125 ][ 126 ], Mn–Sn [ 127 ][ 128 ][ 129 ], La–Sn [ 130 ][ 131 ], Ce–Sn [ 132 ], Cr–Sn [ 133 ] etc., Sn Alloyed with Electrochemically Active Metals: Ge-Sn [ 134 ][ 135 ][ 136 ], Sb–Sn[ 137 ][ 138 ][ 139 ], Ag–Sn [ 140 ][ 141 ], Mg–Sn[ 142 ][ 143 ] etc. Overall, despite the actual progress of portable electronic products, the Sn-M alloy state-of-the-art anode performance still cannot meet advanced LIB requirements for electric vehicles or even grid-level energy storage, which is mainly due to its huge volume change leads to a bad life cycle.[ 9 ]. The recent method of improving the electrochemical performance of Sn-M alloy is introducing electrical conductive hydrogels. Up to now, 3D CPHs have attracted attention due to their larger active surface area, shorter ion and electron transport pathways, and better adaptation to stress at the electrode.[ 144 ][ 145 ]. Some of which will be discussed below in detail. Xu et al., successfully prepared new three-dimensional (3D) polyaniline hydrogel-encapsulated SnCu nanotubes (PANI) (SnCu/PANI). The SnCu nanotubes and the in situ polymerized PANI hydrogel were coated and combined together, as shown in Fig. 8 (a) [ 146 ]. The detailed morphology of Sn-Cu nanotubes anchored by PANI was characterized by SEM and TEM, as shown in Fig. 8 (b) and (c). The superimposed SnCu nanotubes are uniformly dispersed in the PANI hydrogel matrix and fixed by it. The PANI network improves the conductivity of the composite material and prevents the electrode from cracking. The PANI hydrogel intersects the dispersed SnCu nanotubes as a whole, which plays a key role in avoiding direct contact between the SnCu nanotubes and the electrolyte and inhibiting the formation. The unstable SEI film on SnCu nanotubes contributes to excellent electrochemical performance. Figure 8 (d) shows the constant current charge and discharge curve of the SnCu/PANI hydrogel at a current density of 0.1 Ag − 1 . SnCu/PANI initial discharge and charge capacities are 1332 mAhg − 1 and 1034 mAhg − 1 , respectively, which are much higher than commercial graphite anodes. In Fig. 8 (e), the 3D SnCu/PANI hydrogel has a higher capacity than the SnCu nanotube electrode using PVDF as a binder. The former has a capacity of 552 mAhg − 1 , which is higher than the 450 mAhg − 1 of SnCu nanotubes after 300 cycles which is shown in Fig. 8 (f). The constant current cycle curve is performed at 0.1 Ag − 1 . After 500 cycles, the capacity is 584 mAhg − 1 . This is because the porous PANI hydrogel helps to improve the electron transport of the electrode. Figure 10 (g) is the Nyquist diagram of SnCu/PANI hydrogel electrode. The low-frequency linear slope of is relatively large, indicating that the composite electrode has a faster lithium ion transmission rate, which is conducive to high rate charge/discharge. Xu et al., successfully synthesized a unique coral-like 3D Sn-Cu/PANI/GO nanostructured electrode through a simple and scalable solution process [ 147 ] and the general synthesis procedure and detailed structure of the 3D Sn-Cu/PANI/GO hydrogels. The hydrogel is schematically illustrated in Fig. 9 (a). In-situ coating of polymer layer on the surface of Sn-Cu NPs and GO nanoflames can provides electrical connection and maintains structural stability and inhibits Sn-Cu NPs aggregation to further improve electrochemical performance. The morphology and structural information of Sn-Cu/PANI/GO hydrogel electrodes are shown in Fig. 9 (b) respectively. The SEM image demonstrated the hierarchical porous nanostructured Sn-Cu/PANI hydrogel composite electrode. Furthermore, TEM showed that PANI formed a continuous network. As shown in Fig. 9 (d) and (e), a constant current charge/ discharge cycle of 2.0 to 0.01 V was used to evaluate the electrochemical performance of the composite electrode. The Sn-Cu/PANI/ GO hydrogel electrode exhibits improved electrochemical characteristics. Figure 9 (d) demonstrates the result of the potential curve with an increase of 0.2 C. The first discharge / charge cycle provides a specific charge capacity of 1259 mAhg − 1 and a discharge capacity of 1466 mAhg − 1 , which corresponds to a coulombic efficiency of 85%. From cycle 30 to cycle 200, there is almost no change in the charge and discharge curves, indicating that the 3D Sn-Cu/ PANI/GO electrode is very stable during the cycle. Even after 200 cycles at a charge / discharge rate of 0.2 C, the composite can still provide a reversible specific capacity of 693 mAhg − 1 , as shown in Fig. 9 (e). Figure 9 (f) shows the cycling performance of the three electrodes at a current density of 0.2 C. The Sn-Cu/PANI/GO electrode shows excellent cycle performance. This is due to the strong synergy between the 3D conductive network hydrogel and the NP Sn-Cu PANI coating. The coating can inhibit Sn-Cu NPs agglomeration into larger sized particles, which improving cycle stability. Finally, impedance measurement shown in Fig. 9 (g) shows, the GO and 3D porous structure effectively improve the conductivity of the electrode and reduce the contact resistance and charge transfer resistance, which helps to significantly improve reversible ability and speed ability. 3.3. Transitional Metal Oxide (TMO) Based Hydrogels TMOs (MxOy, M = Fe, Co, Ni, Mn, Mo, Cr, Nb, etc.) are attractive candidates because their reversible capacity is about 2–3 times higher than traditional graphite. [ 148 ], [ 149 ], [ 150 ], [ 151 ], [ 152 ][ 11 ]. In particular, MO-type metal oxides have begun research work as LIB anodes [ 153 ], [ 154 ] because of their wide availability in nature, ease of synthesis procedures, and only moderate safety issues. Graphite, as well as eco-friendliness, corrosion resistance and decent cost economy.[ 148 ][ 149 ] [ 150 ][ 151 ][ 152 ][ 11 ]. Several transition metal oxides such as TiO 2 [ 155 ], NiO [ 156 ], SnO 2 [ 157 ], Fe 2 O 3 [ 158 ], CuO [ 159 ], MoO 2 [ 160 ], Co 3 O 4 [ 161 ][ 162 ][ 163 ], CoO [ 164 ] etc., have successfully tested as anodes for LIBs. However, its electrical conductivity is relatively poor and its volume changes greatly during Li + insertion and removal [ 165 ]. The large voltage difference between charge and discharge also leads to low energy efficiency. Therefore, it is still a huge challenge to manufacture high-performance transition metal oxide electrode materials with good cycle stability and speed performance. Several strategies have been developed to improve structural integrity and conductivity such as developing nanostructured TMOs: Co3O4 [ 163 ][ 161 ], CoO [ 166 ] Fe 2 O 3 [ 167 ][ 168 ], SnO 2 [ 169 ][ 170 ][ 171 ], TiO 2 [ 172 ], etc., TMOs with porous structures : porous Fe 2 O 3 microspheres [ 173 ], spherical mesoporous Fe 2 O 3 particles [ 174 ], 1D mesoporous single-crystalline Co 3 O 4 nanobelts [ 175 ], porous Co 3 O 4 nanospheres[ 176 ], porous CoO nanostructure arrays on nickel foam[ 177 ], Mesoporous NiO microspheres [ 178 ], porous Mn 2 O 3 nanoplates [ 179 ] etc., TMOs with hollow structures: hollow Fe 3 O 4 spheres via a simple template-free [ 180 ], multi-shelled Fe 2 O 3 hollow microspheres [ 181 ], Hollow Co 3 O 4 nanospheres [ 182 ], hollow nanospheres of MnO 2 , Mn 3 O 4 and MnO [ 183 ] etc., TMOs based hybrid nanostructured composites: carbon-coated Fe 3 O 4 hollow particles [ 184 ], carbon-coated Fe 2 O 3 nanorods [ 185 ], mesoporous CoO nanorod@carbon nanotube[ 186 ], 1D Fe 3 O 4 /carbon nanowires[ 187 ], 2D Fe3O4/carbon nanosheets [ 188 ], 3D macroporous Fe 3 O 4 /carbon nanospheres [ 189 ], Fe 2 O 3 nanorods/carbon nanofibers composite[ 190 ] and graphene-wrapped Mn 3 O 4 [ 191 ], MnO [ 192 ], Fe 2 O 3 [ 193 ], Co 3 O 4 [ 194 ], and CoO [ 195 ] etc., developing Binary metal oxides: NiCo 2 O 4 [ 196 ][ 197 ][ 198 ], ZnCo 2 O 4 [ 199 ], MnCo 2 O 4 [ 200 ], and CoMn 2 O 4 [ 200 ] etc. However, during lithium ion intercalation/deintercalation, severe aggregations and large volume changes of nanoparticles have been observed [ 201 ], which limits their application in energy storage systems. Recently, 3D graphene such as hydrogel conductive foams, gels and networks, with its high specific surface area, adequate networks, good conductivity and multidimensional electron transport, has launched new research as a cornerstone of building new 3D networked conductive hydrogels[ 202 ]. Zhou et al., prepared a new type of 3D Fe 2 O 3 /rGO hydrogel (FGH) through simple hydrothermal strategy. [ 203 ]. In this hydrogel, rGO sheets self-assemble into an interconnected macroporous structure, and Fe 2 O 3 nanotubes are encapsulated in the rGO layer, as shown in Fig. 10 (a). The SEM image of FGH shows a well-defined and interconnected 3D porous network with pore sizes ranging from submicron to several microns, as shown in Fig. 10 (b and c). This indicates that the Fe 2 O 3 nanotubes in FGH are considered to be enveloped within the pore wall composed of thin stacked layers of RGO sheets. TEM observations further confirmed the uniform distribution of Fe 2 O 3 nanotubes in rGO sheet in Fig. 10 (d). In Fig. 10 (e), we can see the electrochemical performance of the electrode, FGH exhibited a discharge curve similar to Fe 2 O 3 nanotubes in the first cycle, with a discharge slope 0.75 V between approximately 1.29 V and 0.78 V. When cycling at 200 mAg − 1 , the specific capacity of the Fe 2 O 3 nanotubes is significantly attenuated and after 70 cycles it only maintains 63.5 mAhg − 1 . In the case of FGH, although its first discharge capacity (1009.1 mAhg − 1 ) is slightly lower than that of pure Fe 2 O 3 nanotubes (1147.4 mAhg − 1 ), it shows better cycle performance, stabilizing at ~ 700 mAhg − 1 , as shown in Fig. 10 (f). Figure 10 (g) compares the nanotube velocity performance of Fe 2 O 3 and FGH at different current densities. For FGH, reversible capacities of 850, 780, 550, 400, and 280 mAhg − 1 were obtained at current densities of 200, 400, 600, 800, and 1000 mAg − 1 , which significantly exceeded Fe 2 O 3 nanotubes (for example, ~ 100 and 60 mAhg − 1 , 200 and 400 mAg − 1 respectively). When the current density returns to 200 mAg − 1 , FGH can still provide a capacity of up to ~ 600 mAhg − 1 , which means its structure is stable and reversible. The AC impedance spectra of Fe 2 O 3 and FGH nanotubes are shown in Fig. 10 (h). The Nyquist diagram is composed of concave semicircles in the high and mid-frequency regions and straight lines in the low-frequency regions. The result shows that the charge transfer of FGH (16.5 Ω) is lower than that of Fe 2 O 3 nanotubes (73.5 Ω), indicating that a good conductive network is formed due to the incorporation of scales 3D rGO. Bao et al., fabricated a hybrid hydrogel system based on CNTs and CP lattices, which was loaded with TiO 2 nanoparticles to enhance its electrode capabilities in advanced LIB [ 204 ]. The fabrication process is shown in Fig. 11 a. First prepare a homogeneous solution containing PEDOT nanoparticles: water-soluble PSS, CNT and TiO 2 are well dispersed, and then gelling agent is inserted for hydrogel formation, and it can be peeled off as a separate film and cut into hydrogels of different sizes and shapes. The hydrogel is polymerized in-situ to form an interconnected 3D structure, where the CNT is essential to ensure mechanical strength and flexibility. PEDOT: PSS is responsible for the effective transport of delocalized electrons to obtain high conductivity; TiO 2 is selected to achieve high capacity, conductivity and electrochemical stability. As shown in Fig. 11 b, CNTs penetrate the entire structure, while TiO 2 NPs form embedded clusters in the matrix. This network provides the TiO 2 /PEDOT:PSS/CNT electrode with excellent electrical performance, even after 500 repeated bends at a radius of 3.5 mm. The TiO 2 /PEDOT:PSS/CNT electrode shows a higher charge storage capacity in 4000 seconds of charge/discharge, reaching 76 mAhg − 1 compared with the TiO 2 electrode made of polyvinylidene fluoride binder. In addition, the hydrogel system loaded with TiO 2 showed a high area capacity of 2.2 mAhcm − 2 at a rate of 0.1C (Fig. 11 c and 11 d). By combining ideal anode or cathode active materials with CNTs CPHs hybrid systems, batteries with improved mechanical properties and hence electrochemical properties, can be easily manufactured. 3D hydrogels rGO anchored in ultrafine CoO NPs (CoO/rGO nanocomposites) was synthesized using a simple hydrothermal strategy and post-heat treatment process. [ 66 ]. Small sized CoO NPs encapsulated in the hole structure are fixed on rGO nanosheets for CoO/rGO nanocomposites, as shown in Fig. 12 (a). The SEM and TEM images showed that partial overlap or fusion of the flexible RGO nanomembrane resulted in the formation of physical cross-linking sites in the 3D framework shown in Fig. 12 (b) and (c), respectively. It also shows that the high density CoO NPs are uniformly dispersed on the surface of the 3D rGO nano-sheets, with wrinkled and wavy structures, and there is no aggregation of CoO nanoparticles in the CoO/rGO nanocomposites. Electrochemical performance was evaluated by using coin-type batteries. Figure 12 (d) shows that the CoO/rGO nanocomposite charge-discharge curve exhibits a long and extended potential plateau during the first charge/discharge process. The curve is symmetrical in shape, indicating that Li + insertion/removal is highly reversible under different current densities. Figure 12 (e) shows that the CoO/rGO nanocomposite maintains high specific capacities of 890.2, 690.4, 543.8, and 457.0 mAhg − 1 , respectively, even at 200, 800, 1600, and 2400 mAg − 1 , respectively. When the current returns to 100 mAg − 1 , the capacity increases to 1025.8 mAhg − 1 after 82 cycles. CoO NPs and rGO nano-sheets show poor speed capabilities. After cycling 82 times at different current densities, the capacities of CoO NPs and rGO nanosheets were 676.3 and 240.6 mAh g − 1 to 100 mAg − 1 , respectively. Therefore, the retention capacity of the nanocomposite CoO/rGO is better than the other two electrode materials, which is attributed to the well-designed structure with three-dimensional rGO nanosheets. The remaining oxygen-containing functional groups in the graphene nanomembrane after hydrothermal treatment facilitate the formation of covalent forces between the oxide and the matrix, and the large number of pore structures in Li can effectively limit the serious volume change Li + insertion/extraction process of CoO nanoparticles. Then the 3D CoO/rGO nanocomposite showed excellent cycle performance and speed capability. Figure 12 (f) displays the impedance spectra of CoO NPs and CoO/rGO nanocomposites at a potential of 3.0 V after four cycles. The Nyquist diagram is composed of concave semicircles in the high and mid-frequency regions and straight lines in the low-frequency regions. According to the fitting results, the charge transfer of CoO/rGO (45.4) nanocomposites is slightly lower than that of CoO (112.8) nanoparticles, indicating that a good conductive network is formed due to the introduction of rGO three-dimensional nanosheets. Shaijumon, and others [ 2 ] have produced a 3D structure based on reduced graphene oxide (rGO), which has a unique flower-like CoO microstructure, uniformly embedded in the graphene hydrogel matrix (CoO-GHG), thus forming a complete interconnection. shown in Fig. 13 (a). 2]. CoO-GHG exhibits a 3D interconnection structure, with CoO flowers embedded in the 3D graphene lattice, as indicated in Fig. 13 (b), and the TEM image in Fig. 14 (c) shows that the CoO flakes they are embedded in the graphene matrix. The electrochemical activities of CaO and CoO-GHG are shown in Fig. 13 (d) and (e), respectively. The constant current charge/ discharge voltage curves of the CoO-GHG and CoO electrodes cycle Li/Li + in a voltage window of 0.01-3.0 V at a current rate of 100 mAhg − 1 . The initial discharge capacities of CoO-GHG and CoO electrodes were 1230 and 1020 mAhg − 1 , respectively, indicating that the irreversible loss of capacity of the respective electrodes was 20% and 27%. Interestingly, the first discharge capacity obtained by the two electrodes is much higher than the theoretical CoO capacity (≈ 715 mAhg − 1 ), and the higher original CoO capacity after 50 cycles is the result of reversible formation. The CoO-GHG electrode exhibits improved cycle stability, as indicated in Fig. 13 (f), with a very high reversible capacity of 1010 mAhg − 1 , and cycles in excess of 100 at a current density of 100 mAg − 1 times. However, the original CoO electrode showed rather poor cycling performance and its capacity dropped sharply during cycling (Fig. 14 (g), at the same current density of 100 mA g − 1 . 0020, 370 mAhg − 1 was recorded in 100 cycles reversible capacity) Compared with the original CoO electrode, the CoO-GHG electrode has excellent cyclic behavior, which can be attributed to the 3D graphene hydrogel lattice. To further evaluate the excellent electrochemical performance of the CoO-GHG electrode relative to CoO, the velocity performance study tested the two electrodes by cycling at different current rates, namely 100, 200, 400, 800, 1600 and 3200 mAg − 1 (Fig. 13b). At current speed, the capacity is about 300mAh g-1. Under the current of 1600 mAg − 1 , CoO-GHG shows superior speed performance. Compared with the original CoO electrode, it can only hold ≈ 50 at the same current rate. mAhg − 1 . Additionally, in the final 100 mAg − 1 cycle, the CoO-GHG electrode maintained a capacity of 800 mAhg − 1 , while the original CoO electrode was only able to provide a capacity of 410 mAhg − 1 , which indicates the kinetics of the CoO-GHG sample is better than that of the original CoO. It's worth noting that the CoO-GHG electrode achieves high-speed performance without adding additional conductive carbon. This clearly shows that the graphene sheets in the CoO-GHG 3D interconnect network improve conductivity. The synergistic effect of the high conductivity rGO network and the unique flower-shaped morphology of CoO results in an electrochemical performance of the CoO-GHG electrode superior than the original CoO electrode. CoO and CoO-GHG electrodes are cycled at different rates from 100 mAg − 1 to 3200 mAg − 1 [ 2 ]. 4. Conclusion We emphasized how to make hydrogels and integrate them into the LIB active materials, and we provide interesting examples to demonstrate the versatility of hydrogels made from conductive polymers and carbon materials. The creative and combined methods used in the design of functional hydrogels are expected to continue to produce materials with great potential in the field of energy storage. Specifically, a fascinating strategy is to combine CPs or graphene/CNTs with hydrogel electrodes to increase energy storage and power density production; Similarly, combine TMOs and alloys with the conductive hydraulic glue mix. Obtaining the most suitable cycle stability provides a fascinating technique; increasing surface area, porosity, and creating well-connected channels in the form of a hydrogel to promote electron transfer and ion diffusion are expected to improve the electrochemical performance of the battery. Although this article discusses these achievements, ECH development in energy storage systems is still in its early stages. Before transferring high-performance general-purpose ECH to sensitive applications, their manufacturing still faces huge scientific and technological challenges. Compared with typical electrodes, the active materials in LIB electrodes made of ECH have more complex structures and more complex shapes, as well as more complex special elements. These include: (1) The porous hydrogel scaffold provides a huge internal space for the dramatic volume changes of high-energy electrochemical nanoparticles; (2) The uninterrupted conductive community promotes efficient and rapid electron and ion transfer methods; (3) ) The interlocking and interlocking polymer matrix ensures excellent mechanical strength. Looking ahead, continuing to improve CPH performance in exciting energy storage applications requires better control of its electrical, electrochemical, thermal and mechanical properties, as well as chemical and surface functionalization. The development of CH-based materials to synergize the advantages of various components is another future promising approach. At the same time, understand the basic knowledge of CH more deeply, advanced modeling and simulation research is needed. 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Mater Res Bull 62:19–23. 10.1016/j.materresbull.2014.11.010 Chen Z et al (2014) A Three-Dimensionally Interconnected Carbon Nanotube – Conducting Polymer Hydrogel Network for High- Performance Flexible Battery Electrodes. 201400207:1–10. 10.1002/aenm.201400207 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5548724","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":384262132,"identity":"4b816d10-a3c1-4caf-a762-11058aaffd46","order_by":0,"name":"Wondwossen Melaku Yimer","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIiWNgGAWjYJACCQjF3MDYwGADZDA2HiBSCyNISxqYQZKWw2AmXi0Gx3sP3vjwxyZPt72x8ePMtvN2a9sPA22psYnGqeXMuWTLmW1pxWZnDjZLbmy7nbztTCJQy7G03AYcWsxu5JhJ8zYcTtx2I7FB8iFQi9kBoBbGhsP4tfD8+Z+47f7D5p8P284lm51/SIwWtgNAWxjbgA47YGd2g4At9mfOGAP9kpwI9EKb5YxzyQlmN4C2JODxi2R7jyEwxOwStx0/fPhmT5mdvdn59IcPPtTY4NSCARLBKhOIVQ52KSmKR8EoGAWjYGQAALZ1bvNYaMFDAAAAAElFTkSuQmCC","orcid":"","institution":"Jimma Institute of Technology, Jimma University, Jimma, Ethiopia","correspondingAuthor":true,"prefix":"","firstName":"Wondwossen","middleName":"Melaku","lastName":"Yimer","suffix":""}],"badges":[],"createdAt":"2024-11-29 11:30:23","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-5548724/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5548724/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70476124,"identity":"c836dcc1-2d62-40bb-b12a-1fa2a50a55f6","added_by":"auto","created_at":"2024-12-03 14:15:21","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":717782,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesis procedure\u003cstrong\u003e \u003c/strong\u003eof CHs based on CPs. (a) PEDOT:PSS–PAAm organogels \u0026nbsp;[44], (b) PANI bearing boronic acid groups hydrogel crosslinked between PANI and PVA [45], (c) heparin-methacrylate/PANI hydrogel [46], \u0026nbsp;(d) 3D hierarchical microstructure of PANI hydrogel \u0026nbsp;doped and crosslinkrd by phytic acid [47]. (e) CuPcTs doped PPy hydrogel [48]. (g) (ai Schematic diagram of phytic acid replacing some PSS (ii) Schematic diagram of hydrogel and porous network of PEDOT sheet with PANI [49].\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/b02293e0e32ecbd3aea81ebd.png"},{"id":70474622,"identity":"c7076abf-80c4-4b76-8802-b06597aba675","added_by":"auto","created_at":"2024-12-03 13:59:21","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":569175,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the PDA-rGO-PAM hydrogel manufacturing process [58]. (b) (1) Image of GO dispersion before (left) and after (right) hydrothermal reduction. (2) Mechanism of graphene hydrogel formation. (3) graphene hydrogels image prepared by hydrothermal reduction GO concentrations. (4) three columns of graphene hydrogel images, weigning 100 g [59], (c) \u0026nbsp;RGO-based hydrogel synthesis procedure[60] (d). Schematic diagram of preparation process and microstructure of GO-g-PAA/PAM and rGO-g-PAA/PAM hydrogels networks [61]. (e) Preparation procedure of fractal CNT network embedded in GelMA hydrogel. [62].\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/fdbe7ba8fa1fed6c06c56ce8.png"},{"id":70476126,"identity":"e1c78bca-fe25-4a8e-bd05-5b8232f086da","added_by":"auto","created_at":"2024-12-03 14:15:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":432987,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the 3D porous Si/PANI hydrogel; (b) CV curve of PANI and Si-PANI hydrogels electrode at a scan rate of 0.1 mV/s; (c) Polymerization in situ and simple mixing The electrochemical cycle performance of SiPANI composite electrode and pure silicon electrode under charge-discharge cycles; (d) The lithiation/ delithiation capacity and the coulomb efficiency of the Si-PANI electrode at a current density of 6.0 A / g for 5,000 cycles; (e) Constant current charge-discharge curve drawn at 1, 1000, 2000, 3000 and 4000 cycles. [65].\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/fdcb4ba9b6fd47d3d20ff264.png"},{"id":70476127,"identity":"09f343b0-fd17-4096-ad82-4cef21f4a899","added_by":"auto","created_at":"2024-12-03 14:15:21","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":457816,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Si/PPy/CNT ternary electrode structure (b) SEM image of layered Si/PPy/CNT hydrogel, \u0026nbsp;(c) Frequency range of the prepared hybrid electrode between 0.1 Hz and 1 MHz as in Nyquist plots (d) CV curve of Si/PPy/CNT electrode at a scanning rate of 0.1 mVs\u003csup\u003e-1\u003c/sup\u003e, (e) Voltage curve of Si/PPy/CNT electrode, (f) Discharge capacity of the Si/PPy/CNT electrode and Coulombic efficiency [4].\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/e6bef703acb045be1ab80216.png"},{"id":70475011,"identity":"59033f29-b3e2-496e-baa2-0e21c487a402","added_by":"auto","created_at":"2024-12-03 14:07:21","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":419060,"visible":true,"origin":"","legend":"\u003cp\u003ea. SEM images of Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH composites: (a) Si/SiO\u003csub\u003ex\u003c/sub\u003e-1, (b) Si/SiO\u003csub\u003ex\u003c/sub\u003e-2, (c) Si/SiO\u003csub\u003ex\u003c/sub\u003e-3, (d) Si/SiO\u003csub\u003ex\u003c/sub\u003e-4 (or named Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH-1) with inset showing the EDS spectrum, (e) Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH-2, and (f) Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH-3. The arrow indicates cluster of Si/SiO\u003csub\u003ex\u003c/sub\u003e nanoparticles), (a) the cyclic performance of Si-SiO\u003csub\u003ex\u003c/sub\u003e/GH composites and (b) the constant current charge/discharge curve of Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH1 at various current densities shown, (c) Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH-1 Cyclic voltammogram in the first five cycles of 0.1 mVs\u003csup\u003e-1\u003c/sup\u003e. For Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH-1, for an active ingredient of approximately 30 mgcm\u003csup\u003e-2\u003c/sup\u003e, 1 Ag\u003csup\u003e-1\u003c/sup\u003e corresponds to approximately 12 mAcm\u003csup\u003e-2\u003c/sup\u003e.[95].\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/170c0389644b7c86ec1d58e3.png"},{"id":70474626,"identity":"6a124e18-82e8-4087-84e2-02650e2ee22f","added_by":"auto","created_at":"2024-12-03 13:59:21","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":279768,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Diagram of 3D structure of Si nanoparticles with conductive polyaniline polymer (PANI) connected to functionalized sulfonated graphene (SGN) nano-sheets.\u0026nbsp; (b) CV measurement of composite electrode Si/PANI-SGN (red line) and PANI/SGN (blue line). (c) The electrochemical cycle performance of Si/PANI two different electrodes (purple line, a) at a rate of 0.43 mAcm\u003csup\u003e-2\u003c/sup\u003e, and the coulombic efficiency of Si/PANI/SGN (red line, d) and the electrode composed of Si/PANI/SGN (brown line), e) Under a deep charge/discharge cycle of 0.01 to 1 V at a rate of 0.65 mAcm\u003csup\u003e-2\u003c/sup\u003e. (f) Constant current charge/discharge curves of Si/PANI/SGN electrodes cycled at different current densities. (g) The area capacity (mAhcm\u003csup\u003e-2\u003c/sup\u003e) and volume capacity (mAhcm\u003csup\u003e-3\u003c/sup\u003e) of the Si/PANI/SGN composite electrode are cycled up to 5000 times at a rate of 5.2mAcm\u003csup\u003e-2\u003c/sup\u003e (corresponding to 3.2 C\u003cstrong\u003e)\u003c/strong\u003e[96].\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/bf6fa7b337815d9f08100a94.png"},{"id":70475015,"identity":"58457084-db30-4214-9e56-66f2a3d87b32","added_by":"auto","created_at":"2024-12-03 14:07:21","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":270091,"visible":true,"origin":"","legend":"\u003cp\u003eLow (a) and high (b) magnification SEM micrographs of PPy/Si/rGO (c) Cycle data and speed capacity of the electrode based on PPy/Si/rGO and PPy/Si [97].\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/317851a7ee9f6ab97fb13b44.png"},{"id":70476619,"identity":"3b65aa65-8e80-40d2-90bc-3634aa5b1d77","added_by":"auto","created_at":"2024-12-03 14:23:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":371292,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The structure design and manufacturing process of the 3D SnCu/PANI porous electrode (the schematic diagram of the formation of the 3D SnCu/PANI porous electrode). (b) SEM image of the SnCu/PANI hydrogel. (c) TEM image of the SnCu/PANI hydrogel. (d) Constant current charge and discharge curve. (e) Cycle performance of three Sn-Cu-based electrodes. (f) Evaluate performance. (g) Nyquist plot. (e) Cycle performance [146].\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/9d5eadbbb48c639b4ad4ca87.png"},{"id":70476130,"identity":"9e2ed562-b78e-4a1b-83b3-c274bc6f9287","added_by":"auto","created_at":"2024-12-03 14:15:21","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":504421,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Fabrication of 3D Ternary Hydrogel Sn-Cu/PANI/GO; (b) SEM image of the Sn-Cu/PANI composite electrode at different magnification; (c) TEM image of the PANI/GO hydrogel. (d) Voltage distribution of the Sn-Cu/PANI/GO hydrogel electrode at a current density of 0.2 C. (e) Cycle and Coulomb efficiencies of the Sn-Cu/ PANI/GO hydrogel electrode at a density 0.2 C current for 200 cycles. (f) Cycle performance of the Sn-Cu/PANI/ GO, Sn-Cu/PANI and Sn-Cu NP hydrogel electrodes at a current density of 0.2 C. (g) Nyquist graphs of new button cells in the frequency range 1 MHz to 0.01 Hz for Sn-Cu/PANI/GO and Sn-Cu/PANI hydrogel electrodes [147].\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/ea48349b3e3d6698990e775c.png"},{"id":70476617,"identity":"a663f5e7-123b-4487-ae30-9f0e8cc80768","added_by":"auto","created_at":"2024-12-03 14:23:25","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":434210,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of FGH formation process (b and c)) (a) SEM image of FGH Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes. (d) TEM image of FGH. (e) First discharge/charge curve of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and FGH nanotubes at 200 mAg\u003csup\u003e-1\u003c/sup\u003e. (f) Comparison of\u0026nbsp; cycle performance at 200 mAg\u003csup\u003e-1\u003c/sup\u003e current density, (g) Nanotube rate capacity of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and FGH. (h) The AC impedance diagram of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and FGH nanotubes [203].\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/20bfff0107d785163a86c2e8.png"},{"id":70475018,"identity":"994a692a-0b0b-450e-a356-a7c86d102ebd","added_by":"auto","created_at":"2024-12-03 14:07:21","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":77518,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the aqueous solution process of manufacturing PEDOT: PSS/CNT electrode; (b) TiO\u003csub\u003e2\u003c/sub\u003e/PEDOT: SEM image of PSS/CNT thin film electrode; (c) The resistance of TiO\u003csub\u003e2\u003c/sub\u003e/PEDOT:PSS/CNT electrode has a bending radius during 500 bending cycles 3.5 mm; (d) The dependence of the capacity of each electrode on the charging time [204].\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/6852ea8ae54e4368cb3866a6.png"},{"id":70474634,"identity":"1efebd41-501e-4de9-94db-6f378ca071f4","added_by":"auto","created_at":"2024-12-03 13:59:21","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":541515,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the formation mechanism of CoO/rGO nanocomposite, (b) SEM image of CoO/rGO, (c) HRTEM image of CoO/rGO nanocomposite. (D) The charge and discharge curves of CoO/rGO nanocomposites at different current densities between 1, 5, 20, 30, 40, 50 and 70 at 0.01 and 3.0 V (vs. Li\u003csup\u003e+\u003c/sup\u003e/Li). (e)\u0026nbsp;Comparison of the speed capability of rGO nanosheets, CoO nanoparticles and CoO/rGO nanocomposites between 100 mAg\u003csup\u003e-1\u003c/sup\u003e and 2400 mAg\u003csup\u003e-1\u003c/sup\u003e. (f) AC impedance diagram of CoO/rGO nanocomposite and CoO nanoparticles [66].\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/4786e3376421c9d551580c20.png"},{"id":70476133,"identity":"14ae74f4-1578-4b70-86de-2ac120b5950f","added_by":"auto","created_at":"2024-12-03 14:15:22","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":567283,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the synthesis of CoO-graphene hydrogel by hydrothermal technology. (B) SEM image of SEM CoO-GHG image. (c) TEM image of CoO-GHG.\u0026nbsp; (d) Constant current charge/discharge curve of flower-shaped CoO electrode, relative to lithium, cycled at a rate of 100 mAg\u003csup\u003e-1\u003c/sup\u003e. (E)) Constant current charge/discharge curve of the CoO-GHG electrode, relative to lithium, cycled at a rate of 100 mAg\u003csup\u003e-1\u003c/sup\u003e.\u0026nbsp;\u0026nbsp; (f) The capacity retention rate of flower-shaped CoO and CoO-GHG electrodes at a rate of 100 mAg\u003csup\u003e-1\u003c/sup\u003e. (g) Flower shaped\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;CoO and CoO-GHG electrodes are cycled at different rates from 100 mAg\u003csup\u003e-1\u003c/sup\u003e to 3200 mAg\u003csup\u003e-1\u003c/sup\u003e [2].\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/0b8a692d09f00a48102ef4ec.png"},{"id":70476927,"identity":"1ab3cfda-ecff-4813-9a36-4a8266de2ade","added_by":"auto","created_at":"2024-12-03 14:23:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6468381,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5548724/v1/de1295cf-ba0b-467a-b0d2-43fa71d811df.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eDevelopment of Conductive Hydrogel-Based Anode Materials for Lithium-Ion Batteries\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eWith increasing attention to the fossil fuel burgeoning burden, energy disasters and environmental issues, finding a source of sustainable and stable intensity has become the world's top priority. Although various renewable energy sources have been explored and applied to many components of daily activities, including wind energy, geothermal energy, tidal energy, and solar energy, due to the significant fluctuations and unpredictability of climate and environment, seldom widely used. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It is essential to propose efficient energy storage structures, which provide energy to protect the grid when necessary and maintain energy production when there is a surplus of energy production [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Therefore, due to the unexpected increase in global energy consumption, the demand for energy storage and conversion equipment is gradually increasing [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Compared to ordinary storage devices (e.g. as lead-acid batteries, nickel metal hydroxide batteries etc.), rechargeable lithium-ion batteries (LIBs) are the most promising candidates in a series of electric power applications. Because they have the following advantages: extremely high working voltage, high energy density and long life cycle [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In addition to improving the performance of LIBs, the massive efforts of various academic circles and companies remain committed to realizing large-scale energy storage in fully electric vehicles, military and aerospace applications [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Since the overall electrochemical performance of LIBs is closely related to the performance of the electrodes, the choice of electrode materials is extremely important. The negative electrode plays an indispensable role in LIBs, because the characteristics of the negative electrode directly affect the electrochemical performance of the battery. The physical and chemical properties of the active material of the anode determine the behavior of the battery, so it must be considered and managed properly. Some notable characteristics of raw materials certainly provide convenience for your software as active negative electrode materials, but the inherent defects of the materials limit their optimal use. Therefore, in addition to material selection and preparation, excellent modifications and architectural drawings are also essential for increased battery performance [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCarbon-based materials (e.g., graphite) are generally used as anode substances for LIBs due to the fact of their low cost, high abundance and notable kinetics [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, the low operating voltage of graphite, which is close to the voltage of lithium electroplating, can cause protection problems. Its limited theoretical capacity of 372 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e prompts researchers to search for safer and more potential negative electrode candidates. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. To improve the capability of anode materials, full-size interest has been dedicated to alloy-type anode materials, owing to their high precise capacity and safety characteristics [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Among different alloy types of anode materials, silicon (Si) and tin (Sn) are considered promising alternative materials for the next generation of LIB. Si and Sn have theoretical capacities of 4200 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 994 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. They are completely lithiated to the Li\u003csub\u003e22\u003c/sub\u003eSi\u003csub\u003e5\u003c/sub\u003e and Li\u003csub\u003e22\u003c/sub\u003eSn\u003csub\u003e5\u003c/sub\u003e phases, based entirely on the alloying reaction between the respective elements and lithium, which is related to the intercalation mechanism of graphite. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e][\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Furthermore, because silicon has huge exploitable reserves, it can be explored and manufactured at a lower cost. However, before practical application, two major challenges of silicon anodes must be solved. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Other anode materials which are applicable in lithium ion battery are transition metal oxides(TMOs). TMOs (M\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e, M\u0026thinsp;=\u0026thinsp;Fe, Co, Ni, Mn, Mo, Cr, Nb, etc.) are attractive candidates because they can provide about 2\u0026ndash;3 times higher reversibility than traditional graphite Capacity. And eco-friendliness, corrosion resistance and decent cost financial system.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, these anode materials endure a large extent variant throughout cycling, main to poor electrochemical performance[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], and due to the large number of extension exchanges and kinetic and thermodynamic constraints throughout the cycle, they usually exhibit low initial Coulombic efficiency, negative charge capacity, and rapid decay potential.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the final few decades, exceptional effort has been made to conquer the boundaries of Si, Sn and TMOs as anode materials for LIBs using electrical conducting hydrogels (CHs). CH is considered a viable platform for delineating and assembling lithium-ion batteries and other energy storage supplies [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Due to reality, this \"water-based soft material\" synergizes the advantages of hydrogels and electronic conductors, and has high conductivity and mechanical flexibility. It is more suitable for electron and ion transport, as well as for the first-class interface interaction between solid phase and response phase[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis review is devoted to the conductivity of hydrogels, manufacturing methods and their applications in LIB anode materials. The modification aspect of hydrogel in depth, by adding carbon-based materials and conductive polymers to make it conductive. The conductive material can be physically or chemically bonded to the hydrogel matrix. The conductivity is affected by the size of the nanoparticles, the presence of hydrogel-bound water, and the presence of any other components that may affect the conductivity. The review will focus on the application of these conductive hydrogels in lithium-ion battery anode materials.\u003c/p\u003e"},{"header":"2. Electrically Conductive Hydrogels","content":"\u003cp\u003eHydrogel is a cross-linked polymer network that is elastic and packed with a lot of fluid [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] or it is a gel that can contain a required amount of water and swell to a certain degree of balance ( equilibrium extent) in three dimensional (3D) network since it is made up of the terms \"hydro\" (water) and \"gel\"[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The hydrophilic component is answerable for expanding and putting away a lot of water. ECHs are a rising gloriousness of hydrogels joining a hydrophilic framework with electrical conducting fillers, which incorporate metal nanoparticles, conducting polymers and carbon-based substanes [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e][\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. As a result of reversible functionality between swelling and de-swelling, electrical conducting hydrogels (ECHs) can also be designed to have dramatic liquid alternation, quantity or volume changes, and to give a controllable response to different environmental conditions, including ion and light conductivity, electrical or magnetic area. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In general, electrical conducting hydrogels (ECHs) have huge promises in different packages in renewable electricity, [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e][\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], and environmental engineering [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] to medical devices[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e][\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] and drug delivery structures[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e][\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Conducting Polymer based Hydrogels\u003c/h2\u003e \u003cp\u003eConductive polymers (CPs), which include poly(acetylene, aniline, pyrrole, thiophene, (phenylene vinylene), etc.)[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], are similar to metals and semiconductors in that they have electrical and optical properties while maintaining the properties of ordinary polymers. It has the characteristics of a cheap, simple and flexible synthesis method. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. They are versatile in that their properties can be easily adjusted by surface functionalization and /or doping. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The basic performance of charge propagation in CPs is mainly based on the following two mechanisms: (i) the transfer of delocalized electrons through conjugated systems such as polypyrrole (PPy) and PANI) etc., and (ii) the transfer of electrons via the mobile electron exchanges and reacts between adjacent redox sites in the redox polymer [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] (electron jumping). Conductive CP makes it an important category of materials, with wide applications [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], mainly used for energy storage[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e][\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e][\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], electrochromic screens [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], electrocatalysis and photocatalysis [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], and sensors [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], etc.\u003c/p\u003e \u003cp\u003eConductive hydrogel is the name used to define the hybrid network formed by the combination of cross-linked hydrogel and CP. They have similar properties to traditional hydrogels, but have the additional advantage of electrical conductivity. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. CPH is a material that generally contains CP together with a carrier polymer. Due to its special structure, CPH has some interesting characteristics, such as: high water content, softness, plasticity and mechanical integrity, porosity and high surface specificity.[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. In addition, they are characterized by mixed electronic and ionic conductivity, redox activity, and conversion between conductive and insulating forms in CPs. Mostly used conductive components in CPHs are PANI, PPy and PEDOT [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e][\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e][\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e][\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e][\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The most studied synthetic method for forming CP hydrogels is to polymerize CP using a hydrogel matrix that has already been manufactured. [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGenerally, the following manufacturing routes have been studied to develop CPHs. The first is to gel the CPs and the hydrophilic polymer/ monomer mixture by self-assembly or by introducing cross-linkable elements. In this case, the conductivity of this hydrogel can usually be improved by increasing content of the conductive polymer. The organogel conductor was synthesized by this method. [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Lee et al. Synthesized organogel PEDOT: PSS/Acrylamide [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], which is composed of poly (3,4 ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), polyacrylamide (PAAm) and glycol solvent. The detailed synthesis process is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. PEDOT: PSS provides a conductive pathway for the organogel to transmit electrical signals and PAAm, because the cross-linked polymer network makes it highly flexible and stretchable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAnother method is to grow CP on a precast hydrogel by chemical oxidation and electrochemical polymerization. The conductivity of CPHs can be used for different purposes in a wide range by controlling the amount of polymerization of CPs. In this way, Li et al. synthesized PANI PVA hybrid conductive hydrogel through dynamic borate bonding.[\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. PVA act as a soft polymer and makes the hybrid hydrogels have excellent mechanical properties, while PANI act as a rigid polymer and provides enhanced electrical properties and stability. PANI can be cross-linked with PVA through the boronic acid group in PANI to form a strong CH with the mesoporous structure indicated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. Furthermore, electrochemical polymerization can also be used to develop CPs in prefabricated hydrogels[\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e][\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. ECHs manufacturer inspired by this work from many hydrogels (PAM, PAA, PVA, agarose, and chitosan) and many CPs (polypyrrole, polyaniline, and polyethylene dioxythiophene)[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e][\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e][\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. In a study published by Ambrosio et al., [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], the aniline monomer was first dissolved in a polyethylene glycol diacrylate (PEGDA) solution; then UV polymerization was carried out to build a cross-linked hydrogel with a super-porous structure network.\u003c/p\u003e \u003cp\u003eAnother ECH fabricated was PANI/heparin-methacrylate hydrogel, its synthetic method is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. First, the bio-based heparin hydrogel network is formed by UV curing; then it is immersed in the aniline solution to diffuse the monomer into the porous structure. Finally, PANI/heparin methacrylate hydrogel is formed by the oxidative polymerization of aniline, and PANI is physically embedded in the heparin methacrylate hydrogel matrix. Yeen and others [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e] used polyaniline (PANI) and polyacrylamide (PAA) to prepare a conductive hydrogel. PANI/PAA hydrogel is prepared by the interfacial polymerization method. Various characterization tests were performed in order to study the properties of CHs, such as FTIR, conductivity test, swelling test, and compression test. The results were compared with non-conductive PAA hydrogels. The incorporation of PANI into PAA hydrogel significantly improves the conductivity of the hydrogel. Compared with PAA hydrogel, the swelling rate of PANI/PAA hydrogel is reduced, and Young's modulus is increased.\u003c/p\u003e \u003cp\u003eThe third method involves the use of doped molecules to crosslink CP chains through multiple functional groups to produce several CPHs that do not contain insulating components [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e][\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Among them, Bao et al., they first described phytic acid to form PANI hydrogels [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. The gel formation mechanism of PANI hydrogel is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. This type of CPH has high conductivity because it avoids the use of insulating components and builds a 3D conductive polymer network, which promotes electron transport and ion diffusion. In addition to phytic acid, copper phthalocyanine-3\u0026rsquo;, 4\u0026rsquo;, 4\u0026rsquo;\u0026rsquo;, 4\u0026rsquo;\u0026rsquo;\u0026rsquo;,-tetrasulfonic acid tetrasodium salt can be used to form polypyrrole hydrogel by crosslinking polypyrrole chains[\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. The interfacial polymerization strategy was used to prepare nanostructured conductive PPy hydrogels at the organic/water two-phase interface as reported by Yu \u003cem\u003eet al\u003c/em\u003e. [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. CuPcTs and PPy are connected to each other and form a PPy fiber, which crosslinks into a hydrogel. Dopants CuPcTs are used as gelling agents to self-assemble 1D PPy nanofibers \"collar-shaped\" into a 3D hydrogel networks via electrostatic interaction and H-bonding as indicated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee. Chen et al., synthesized a hydrogel by integrating two types of conductive polymers PANI and PEDOT using phytic acid as the molecular bridge[\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Some of PSS replaced by the acid and promotes the conversion of the PEDOT chain from the benzoic acid structure to the quinone structure. The resulting hydrogel is composed of a 3D network of PEDOT sheets embedded with PANI; due to the molecular interaction between PANI and PEDOT. Compared to PEDOT hydrogels, it has greatly improved mechanical properties. Since each phytic acid molecule has six phosphate groups, it can interact easily with the PEDOT and PANI chains. Phytic acid used as a molecular bridge and cross-link PANI and PEDOT at the molecular level in order to form a PEDOT/PANI hydrogel. The gel mechanism is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg (i). During the gelling process, it produces an independent PEDOT/PANI hydrogel of high mechanical strength. The independent PEDOT/ PANI hydrogel is composed of a 3D network of PEDOT sheets; PANI particles appear to be embedded in each foil, promoting rapid transmission of electrons and ions, resulting in high capacitance performance. Each paper features a rough surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg(ii)) rather than the smooth surface of separate PEDOT or PANI hydrogel, meaning that PANI is successfully integrated into PEDOT.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Carbon material-based hydrogels\u003c/h2\u003e \u003cp\u003eCarbon materials, such as carbon nanotubes (CNT), graphene, activated carbon, carbon fibers, carbon dots, and porous carbon, are considered conductive due to their unique high conductivity, excellent environmental stability. and low cost production and promising conductor material for hydrogel [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e][\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e][\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. From various carbon materials, carbon nanotubes and graphene have been extensively explored in materials science, and is used as conductive fillers in conductive hydrogels for flexible and portable electronics products. Due to its electrical, thermal and mechanical properties, it has played an important role in a wide range of research fields. Their improved electrical properties are very attractive, suggesting that they can be used as reinforcing materials and additives for composites [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. Self-assembly of mixed and modified with various polymers, the two most common methods for preparing conductive carbon-based hydrogels. Some carbon-based hydrogels are discussed below.\u003c/p\u003e \u003cp\u003eThe conjugated structure graphene cannot be uniformly dispersed in water, which limits its application in the manufacture of conductive hydrogels. Modified hydrophilic polymer is an effective way to promote good dispersion of graphene in H\u003csub\u003e2\u003c/sub\u003eO. Polydopamine (PDA) can cover almost all nanomaterials, so nanomaterials have a good dispersion in the hydrogel network. On this basis, Han's team designed a partially reduced graphene oxide (pGO) PAAm hybrid hydrogel with conductive PDA[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea illustrates synthesis process to form a hydrogel. First, GO is dissolved and reduced partially in the PDA solution, and obtained by polymerizing dopamine under oxidizing and alkaline conditions. Then, CHs were developed by polymerizing acrylamide monomers in the presence of rGO. The fully reduced GO (rGO) can be uniformly dispersed in the PAAm hydrogel lattice and act as an electronic pathway, so that the conductive hydrogel has good conductivity. GO which is not reduced by oxygen-containing groups can interact with the PAAm chain through H-bonding and electrostatic interaction. PDA also interacts with the PAAm chain through π-π stacking and H-bonding. These synergistic effects of non-covalent interactions give the CHs toughness and high stretchability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSelf-assembled graphene hydrogel with a cross-linked three-dimensional porous structure synthesized by Shi et al., (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb1)[\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. The uniform suspension of GO sealed in an autoclave and kept at 180 \u0026deg; C. After heating for 12 hours without any interference, and then the autoclave is cooled to room temperature and the graphene hydrogels are formed through supramolecular interactions such as H-bonding, electrostatic interaction, and π-stacking (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb2). The characterstics of graphene hydrogels highly dependent on the GO concentration during the process. As the amount of GO is low, only black powder is formed. And increasing the amount of GO, a well-defined graphene hydrogel can be formed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb3). hydrazine or hydroiodic acid used to further treat the dispersed graphene hydrogel to remove residual oxygen containing functional groups and improve conductivity. This study provides a method to construct three dimensional (3D) hydrogel networks from 2D graphene sheets, which has inspired a number of new designs of graphene-based hydrogel networked systems. The graphene hydrogels obtained by this method exhibit a clear networked structure with high mechanical strength (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb(4)), but if they do not contain a hydrophilic polymer matrix and therefore lack the ability to retain a large amount of liquid .\u003c/p\u003e \u003cp\u003eAnother type of rGO-based hydrogel is synthesized by encapsulating it in PEGDA hydrogel (CTS-g-GMA). First, the CTS was modified by GMA grafting to obtain the photo-crosslinkable group in its skeleton (methacrylation degree: 7%). Then, rGO is encapsulated in PEGDA hydrogel (CTS-g-GMA) to make conductive hydrogel, because rGO has the advantages of low preparation cost, two-dimensional planar structure, large specific surface area, and dispersibility in many organic solvents and water. Due to its reactive side groups (OH and COOH), rGO molecules interact with the polymer network formed by the photopolymerization process between CTS-g-GMA and PEGDA, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec. In order to create a chemical cross-linking network, GMA graft-modified CTS was used as the main component, and PEGDA was used as a cross-linking agent due to its acrylate group. A PEGDA hydrogel without rGO (CTS-g-GMA) was also synthesized to predict effect of rGO on the physico-chemical characterstics of the hydrogels. [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLi et al. [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e] proposed a strategy to make a strong, self-healing and conductive hydrogel containing rGO. The grafted polyacrylic acid GO (GO-g-PAA) fabricated incorporated it into a chemically cross-linked PAM network to get GO-g-PAA/PAM hydrogel, which is subsequently treated with ascorbic acid solution at room temperature and passed rGO-g-PAA/PAM to obtain a hydrogel. The reversible H-bond between the grafted PAA chain and the PAM matrix increase the interfacial interaction between GO/rGO and the hydrogel matrix. Therefore, both GO-g-PAA/PAM and rGO-g-PAA/PAM hydrogels have improved tensile properties, excellent energy dissipation, and rapid self-recovery. In situ chemical reduction of GO-g-PAA in the hydrogel matrix causes the rGO-g-PAA/PAM hydrogels to have good electrical conductivity and significant changes in tensile strength.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed shows a schematic diagram of the synthesis of GO-g-PAA/PAM and rGO-g-PAA/ PAM hydrogels. At the begning, GO-g-PAA is synthesized from GO, dispersed in water, and neutralized with NaOH to form a long-term stable aqueous solution. Next, use MBA as a chemical crosslinking agent in GO-g-PAA aqueous solution to perform AM in situ polymerization to obtain GO-g-PAA/PAM hydrogels. Finally, ascorbic acid was used as a reducing agent to perform a mild in situ chemical reduction of GO-g-PAA in the hydrogel matrix [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e] inorder to obtain rGO-g-PAA/ PAM hydrogels. The GO-g-PAA/PAM hydrogels observed to be brown with the naked eye. The rGO-g-PAA/PAM hydrogel is black, indicating a decrease in GO-g-PAA. GO-g-PAA and rGO-g-PAA not only act as nanofillers, but also act as multifunctional physical crosslinkers in the hydrogels by grafting the H-bonds between the PAA chains and the PAM matrix. [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. The reversible hydrogen bond between the grafted PAA chain and the PAM matrix improves the interfacial interaction between GO/rGO and the hydrogel matrix. Due to improved interface compatibility and effective energy dissipation, GO-g-PAA/ PAM and rGO-g-PAA/PAM hydrogels exhibit improved tensile mechanical properties and exhibit good self-healing capabilities, and exhibits satisfactory conductivity. The combination of these properties, make rGO-g-PAA/PAM hydrogels more widely used in different applications.\u003c/p\u003e \u003cp\u003eApart from graphene, CNTs have widely incorporate into hydrogel networks due to their tube like structures and highest electrical properties. As described in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, gelatin methacrylate hydrogel (GelMA) incorporating CNTs is prepared by in-situ polymerization through ultraviolet radiation [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. The uniform inclusion of CNTs in the hybrid hydrogel can be attributed to the uniform dispersion of the GelMA-coated CNTs in the prepolymer solution. Uniform crosslinking of GelMA coated CNTs through acrylic groups results in a network structure.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conducting Hydrogels Used in Lithium-Ion Battery","content":"\u003cp\u003eOver the years, researchers have designed hydrogels in various ways to meet the considerable requirements of LIB electrodes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e][\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e] [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e][\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e][\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e][\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e]. The following table lists the electrochemical characteristics of some ECH incorporated into the active electrode of LIBs and compared. The active anode materials are Si, tin metal alloy and transition metal oxides. ECH is currently used substances that specify LIB, and given their electrochemical and physical properties, the following dialogue will focus on intentional ECHs.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Silicon based Hydrogels\u003c/h2\u003e \u003cp\u003eFor every one silicon atom, four lithium atoms can be bound to form Li\u003csub\u003e22\u003c/sub\u003eSi\u003csub\u003e5\u003c/sub\u003e [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e], Si anode encounters problems inclusive of massive extent change (300\u0026ndash;400%) after lithiation/delithiation cycles ensuing mechanical fracture, loss of interparticle electric contact and repeated side reactions with electrolytes, it has not yet been broadly commercialized [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e]. Several improvements have been developed to increase the electrochemical performance of Si-based LIB anodes. Design Si nanostructures: Si nanocrystals [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e] nanowires [\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e], core-shell nanofibers [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e][\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e], nanosheets [\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e], nanotubes [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e], nanospheres [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e], Si nanoporous [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e], Si/carbon nanocomposites [\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e], [\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e], Si NPs coated by graphene [\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e] [\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e][\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e], and applied polymer binders to Si nanoparticle electrodes such as PAA-P (HEA-co-DMA)[\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e], PAA-UPy [\u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e], PAA-PBI [\u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e], PD/PAA [\u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e87\u003c/span\u003e], CS-PAA [\u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e], etc. However, since the electrode still suffers weak mechanical binding, nanoparticle agglomeration, poor network contact and pulverization during cycling because of large volume change during lithation/delithation[\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e], and applying the new class of polymeric materials are become known which are conductive polymer hydrogels. Hydrogels are 3D networks of crosslinked polymer chains that readily take in water and swell without dissolving [\u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e]. They are highly flexible because of their high water content. The hydrogels are capable of providing high ionic conductivity, electronic conductivity [\u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e], electrochemical activity [\u003cspan citationid=\"CR92\" class=\"CitationRef\"\u003e92\u003c/span\u003e], structural flexibility [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and electrolyte permeability [\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e] to improve energy-storage device performance. Hydrogels from conductive polymeric materials have been explored for a broader range of applications, such as energy conversion and storage, sensors, actuators, medical and biological equipment, and superhydrophobic coatings. [\u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e94\u003c/span\u003e]. Some of Si based conductive polymer hydrogels anode materials which has been used for lithium ion battery are discussed below.\u003c/p\u003e \u003cp\u003eWu et al., synthesized ECH matrix Si/PANI hydrogel anode material by in situ polymerization [\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e].. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea shows that each SiNP is encapsulated in a conductive polymer floor covering and similarly connected to a highly porous hydrogel framework. Through interaction between the surface OH groups and the phosphonic acid in the phytic acid molecule of the crosslinking agent (right column), or due to the electrostatic interaction between the negatively charged OH groups and the positive cost PANI due to the Phytic acid doping, the SiNP has been lined according to the polymer layer. The Si -PANI hydrogel is then covered with a modern copper foil current collector for electrochemical measurement. The CV experiment for both PANI and Si-PANI hydrogel was realized in a capacity window of 0.01-1 V at a scan rate of 0.1 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in half of the cells, instead of Li/Li\u003csup\u003e+\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). The results show that Si contributes to the capacity of the entire electrode in most areas. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, at a modern density of 1.0 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the well-known Si/PANI composite shows a constant capacity of 1600 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 1,000 cycles, which is much higher than the use of binders, silicon ordinary nano silica or the easy combination of SiNPs and PANI. The composite electrode has a perfect capacity at 2500 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the charge-discharge rate is between 0.3 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 3 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and the high current / potential lithiation slope during charge and discharge is between 0.3 and 0.01 V 3.0 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed and e shows that a composite electrode with a capacity of ~\u0026thinsp;550 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e can maintain a capacity of 91% after 5000 cycles at a current density of 6 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which confirms its better cycle stability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eYu et al., prepared a 3D Si/PPy/CNT ternary conductive hydrogel anode electrode [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], They reported on a new type of silicon anode, consisting of a porous, three-dimensional (3D) layered nanostructure with electrically conducting single-walled carbon and Si NPs composition in a polypyrrole (PPy) framework. Nanotubes (SWCNT) are used as electron enhancers, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea.\u003c/p\u003e \u003cp\u003eThe continuous PPy framework provides a unique porous structure to promot electron and ion transport adapt to the enormous volume changes of Si NPs. The SWCNTs used as the housing and electrical conductive structure further enhancing the integration of Si/CP structure and the electrical conductivity of the electrode, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb. EIS performed to check the lithiation/delithiation stability of the Si-PPy/CNT during the electrochemical process. The result of the Nyquist diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) of the hydrogel electrode shows no significant increase in impedance was detected after cycling, indicating that due to the unique hybrid electrode design and high efficiency in the cycling process, electron/ion transport through the porous electrode in 3D layers in between.\u003c/p\u003e \u003cp\u003eThe CV of the Si-PPy/CNT hydrogel electrode is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed. A high redox peak near 0.2 V corresponds to the Si-Li alloy reaction, and two clear correlations are observed related to the delithiation of Si at 0.40.6 V. Redox peak. As the SiNPs that react with lithium are gradually activated, the size of all current peaks increases with increasing number of cycles in the first cycle and the addition of SWCNT to the Si-PPy binary electrode system increased chemical reversibility of the electrical energy of the ternary electrode. The first discharge capacity of the hydrogel electrode is 3600 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is about 10 times that of the traditional graphite anode (372 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). It then stabilized at about 1600 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in 1000 cycles. Within the potential window of 0.01 to 1 V, the capacity retention rate was 86% compared to Li/Li\u003csup\u003e+\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). Furthermore, the coulombic efficiency of the Si-PPy/CNT electrode was 78.2% in the first cycle and 99.5% in subsequent cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eJiang et al., synthesized porous 3D Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH conductive hydrogel successfully composited to fabricate LIBs anode materials [\u003cspan citationid=\"CR95\" class=\"CitationRef\"\u003e95\u003c/span\u003e]. These compounds are composed of self-assembled 3D Graphene (GH) networks in which embedded silicon NPs, are covered with an ultra-thin layer of SiOx. SEM image in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows that Si/SiO\u003csub\u003ex\u003c/sub\u003e NPs are uniformly dispersed in the GH structure. Despite the presence of the SiO\u003csub\u003ex\u003c/sub\u003e coating (as indicated by the arrow), other NPs are still aggregate in micron-sized clumps. However, as the thickness of the SiO\u003csub\u003ex\u003c/sub\u003e coating increases, the average size of the agglomerates decreases, and hence it improves the overall dispersion of the Si/SiO\u003csub\u003ex\u003c/sub\u003e NPs. It is worth noting that changing the weight load of Si/SiO\u003csub\u003ex\u003c/sub\u003e has little effect on the microstructure of the composite material. Therefore, an ultra-thin layer of SiO\u003csub\u003ex\u003c/sub\u003e is manufactured on the surface of the Si NPs in order to improve their dispersion in the matrix and hence improve their interfacial adhesion with graphene sheets. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb shows that the Si/SiO\u003csub\u003ex\u003c/sub\u003e/GH composite constructed electrode shows excellent speed performance (1020 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 4 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) with good cycle stability (1640 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, at 10 and 140 at 0, 1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) Maintain 80 \u0026deg; speed between cycles), where the Si/SiO\u003csub\u003ex\u003c/sub\u003e/C value of is considered favorable (520 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 4 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with 75% by weight of Si/SiO\u003csub\u003ex\u003c/sub\u003e). In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, a slight gradient appears in the range of 0.3 to 0.6 V, corresponding to the lithation of Si and delithation of Li\u003csub\u003ex\u003c/sub\u003eSi phase, respectively. This means that an increase in current density has almost influenced the shape of the curve. The CV profile of the composite electrode if SiO\u003csub\u003ex\u003c/sub\u003e/GH is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. In scanning of the anode, a peak was observed at 0.74 V, 0.01 V and 0.15 as the degradation of the electrolyte and the formation of the SEI film is shown. As lithation of Si and GH, indicates the formation of the SEI layer, and the formation of several phases of LiSi, respectively. In an anode price, two apparent peaks of 0.35 and 0.5 V showed disinposition of the LiSi alloy. Excellent electrochemical performance can be attributed to 3D opening and porous structures of GH openings and 3D porous structures that can be adapted to a large internal space and volume change of nanoparticles and highly porous 3D structures there.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOh, \u003cem\u003eet al\u003c/em\u003e., they reported [\u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e96\u003c/span\u003e] a 3D self-assembled Si/PANI-SGN porous nanocomposite electrodes, prepared by a low-cost, scalable, complete solution processing method, using aniline is a monomer to form a PANI, SGN as a 3D soft template and as an electrical enhancer in the presence of SiNPs, followed by oxidative polymerization in situ by ultrasonic treatment. Since SGN is interconnected with PANI, SGN forms a smooth porous structure. At the same time, when SiNPs was added to PANI-SGN nanocomposites with a small amount of PA, the SiNPs- PANI/SGN/PA compounds showed that PANI-SGN hydrogels embedded together to form porous nanostructures, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea.. Electrochemical performance is expressed as follows. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, the CV measurement is performed on the potential window of 0.01-1.0 V with respect to Li/Li\u003csup\u003e+\u003c/sup\u003e at a scanning speed of 0.1 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in a half-cell. The peak observed at 0.19 V corresponds to the conversion of crystalline Si to the Li\u003csub\u003ex\u003c/sub\u003eSi phase, while the two peaks at 0.43 and 0.51 V correspond to amorphous (α) α-Li\u003csub\u003ex\u003c/sub\u003eSi delithiation to α-Si. The expanded peak potential separation between the anode peak and the cathode peak indicates that the electrochemical reversibility of the ternary electrode which is enhanced by adding SGN to the Si/PANI binary electrode system. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec shows that the electrochemical performance of the Si/PANI/SGN composite electrode is significantly higher than that of the Si/PANI electrode under a deep charge-discharge cycle of 1 to 0.01 V, and maintains a stable capacity (red line, b) for a long period of time. The coulombic efficiency stabilizes around 100% in long cycles. Furthermore, these results indicate that by protonating the nitrogen group in PANI, SGN reacts with the aniline monomer and can be used as an excellent gelling agent, electrical conductor and reinforcing agent. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed anode shows that the first cycle EC is ~\u0026thinsp;78% (discharge capacity, 1.87 mAhcm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e charge capacity, 1.45 mAhcm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), and easily increases to 91% in the second cycle, and finally stabilizes above 99.5%. Then cycle at a rate of 0.33 mAcm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. From the lowest current density to the highest, we found that the Si/PANI/SGN composite material holds the alloying and unlocking deck well. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee, the reversible lithium extraction capacity and excellent EC are found to be consistent with the robust performance of the electrode under high current density at a rate of 5.2 mAcm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e for up to 5000 charge-discharge cycles 3.2C. Compared to Si/PANI, the improved speed performance of the ternary anode Si/PANI/SGN further confirms the advantages of SGN as an electronic enhancer. These results also support that the conductive polymer SGN hydrogel structure provides a channel for rapid electron transmission, thus providing excellent speed capability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOzkan et al., synthesized the rGO wrapped PPy/Si electrodes using a solution-based sol-gel polymerization process [\u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e97\u003c/span\u003e]. SEM micrograph shows the structure and morphology of the PPy/ Si/rGO compound in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea. Due to hydrogen bonding and electrostatic interactions between the ternary components: Si, pyrrole, and phytic acid in the precursor, the polymerized PPy hydrogel produces a uniform coating to encapsulate the Si. Before polymerization, the diameter of the Si ranged from 50 to 70 nm. A gel-like conductive layer was formed with a thickness of 10\u0026ndash;20 nm to coat Si, which was confirmed by the increase in diameter of Si at 80\u0026ndash;90 nm after polymerization, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb. The PPy coating helps maintain the integrity of the solid electrolyte interface (SEI) layer during the expansion process. The PPy gel also generates a continuous conductive frame to shorten the transmission length of electrons and ions while preventing the SINP from separating from the electrode. The rough surface has a 30\u0026ndash;60 nm nanopore, which aids in the rapid diffusion of lithium ions, and the micropore reduces Si volume expansion during the lithiation process (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). It is worth noting that the PPy/Si are wrapped in the rGO sheet or covered flat with rGO on the surface of Si. Therefore, rGO can improve the electrochemical stability of the network because its functional groups (such as carboxyl and hydroxyl) bind to the surface of PPy/Si. In addition, the excellent conductivity of rGO can promote the transfer of electrons and charges, thus improving the rate performance.\u003c/p\u003e \u003cp\u003eHere, silicon NPs are coated with CHs and wrapped in rGO sheets through a simple solution-based sol-gel process. In-situ polymerized PPy hydrogel forms an interconnected 3D fiber matrix. The amine and OH groups of the hydrogel help to encapsulate Si through hydrogen bonding. Constant current charge, discharge and cycle performance are measured in the voltage range of 0.01 to 1 V (compared to Li\u003csup\u003e+\u003c/sup\u003e/Li). Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec shows the speed capability of the PPy/Si/rGO composite electrode up to 2.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with up to 500 additional cycles at 2.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The first cycle is performed at 0.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, followed by 9 cycles at 0.2 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 10 cycles at 0.4 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This process is necessary to fully activate Si while promoting the formation of stable SEI confirmed by the cycle. The first discharge capacity of the PPy/Si/rGO electrode is 3323 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the charge capacity is 2639 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the corresponding coulombic efficiency is 79.4%. After being discharged at a high rate of 2.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the PPy/Si/rGO electrode showed reversible capacities of 1312, 1285 and 1066 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 100, 250 and 500 cycles. The average Coulombic efficiency (\u0026gt;\u0026thinsp;99%) of the cycle at 2.1 A g1 indicates that the PPy/Si/rGO anode has good stability and reversibility. In contrast, PPy/Si without rGO sheets showed a capacity of 742 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 500 cycles at 2.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Support for the addition of rGO greatly improved the stability and velocity performance of the electrode. Constant current charge/discharge curve. The excellent performance of the anode can be attributed to several factors including the interconnected layered PPy framework, the formed Ppy coating on the SiNPs, and the addition of rGO flakes as a conductive additive for the PPy/Si electrode.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Tin (Sn-M, M\u0026thinsp;=\u0026thinsp;Cu, Ni, Fe) alloys based hydrogels\u003c/h2\u003e \u003cp\u003eDue to the massive deposition of tin in nature and the high theoretical capacity of approximately 994 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, tin-based materials are considered as promising anode alternatives [\u003cspan citationid=\"CR98\" class=\"CitationRef\"\u003e98\u003c/span\u003e][\u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e99\u003c/span\u003e]. However, the low capacity retention rate and rate capacity are usually attributed to the huge volume change during the Li\u003csup\u003e+\u003c/sup\u003e insertion and removal process, which not only leads to severe splashing of the current collector and subsequent power failure, but also leads to unstable SEI in Sn surface. [\u003cspan citationid=\"CR100\" class=\"CitationRef\"\u003e100\u003c/span\u003e]. To overcome such problems, several strategies has been developed: (i) Developing various nanostructures of Sn and Sn-based nanoscale materials: monodisperse Sn nano particles[\u003cspan citationid=\"CR101\" class=\"CitationRef\"\u003e101\u003c/span\u003e] Sn/SnO\u003csub\u003e2\u003c/sub\u003e nanoparticles [\u003cspan citationid=\"CR102\" class=\"CitationRef\"\u003e102\u003c/span\u003e], nanoporous Sn NPs [\u003cspan citationid=\"CR103\" class=\"CitationRef\"\u003e103\u003c/span\u003e][\u003cspan citationid=\"CR104\" class=\"CitationRef\"\u003e104\u003c/span\u003e], Sn, SnS, and SnO\u003csub\u003e2\u003c/sub\u003e nanocrystals[\u003cspan citationid=\"CR105\" class=\"CitationRef\"\u003e105\u003c/span\u003e], dispersing Sn nanoparticles in Carbon Matrix [\u003cspan citationid=\"CR106\" class=\"CitationRef\"\u003e106\u003c/span\u003e], Ultra-small Sn NPs embedded in nitrogen-containing porous carbon[\u003cspan citationid=\"CR107\" class=\"CitationRef\"\u003e107\u003c/span\u003e], nanostructured Sn/nitrogen-doped carbon composites (Sn/NCs) [\u003cspan citationid=\"CR98\" class=\"CitationRef\"\u003e98\u003c/span\u003e] etc., alloying of Sn with electrochemically inactive metals: amorphous Sn\u0026ndash;Co\u0026ndash;C composites [\u003cspan citationid=\"CR108\" class=\"CitationRef\"\u003e108\u003c/span\u003e], Fe\u0026ndash;Sn [\u003cspan citationid=\"CR109\" class=\"CitationRef\"\u003e109\u003c/span\u003e][\u003cspan citationid=\"CR110\" class=\"CitationRef\"\u003e110\u003c/span\u003e][\u003cspan citationid=\"CR111\" class=\"CitationRef\"\u003e111\u003c/span\u003e][\u003cspan citationid=\"CR112\" class=\"CitationRef\"\u003e112\u003c/span\u003e], Co\u0026ndash;Sn [\u003cspan citationid=\"CR113\" class=\"CitationRef\"\u003e113\u003c/span\u003e][\u003cspan citationid=\"CR114\" class=\"CitationRef\"\u003e114\u003c/span\u003e][\u003cspan citationid=\"CR115\" class=\"CitationRef\"\u003e115\u003c/span\u003e][\u003cspan citationid=\"CR116\" class=\"CitationRef\"\u003e116\u003c/span\u003e][\u003cspan citationid=\"CR117\" class=\"CitationRef\"\u003e117\u003c/span\u003e][\u003cspan citationid=\"CR118\" class=\"CitationRef\"\u003e118\u003c/span\u003e][\u003cspan citationid=\"CR119\" class=\"CitationRef\"\u003e119\u003c/span\u003e], Cu\u0026ndash;Sn [\u003cspan citationid=\"CR120\" class=\"CitationRef\"\u003e120\u003c/span\u003e][\u003cspan citationid=\"CR121\" class=\"CitationRef\"\u003e121\u003c/span\u003e][\u003cspan citationid=\"CR122\" class=\"CitationRef\"\u003e122\u003c/span\u003e][\u003cspan citationid=\"CR123\" class=\"CitationRef\"\u003e123\u003c/span\u003e], Ni\u0026ndash;Sn [\u003cspan citationid=\"CR124\" class=\"CitationRef\"\u003e124\u003c/span\u003e][\u003cspan citationid=\"CR125\" class=\"CitationRef\"\u003e125\u003c/span\u003e][\u003cspan citationid=\"CR126\" class=\"CitationRef\"\u003e126\u003c/span\u003e], Mn\u0026ndash;Sn [\u003cspan citationid=\"CR127\" class=\"CitationRef\"\u003e127\u003c/span\u003e][\u003cspan citationid=\"CR128\" class=\"CitationRef\"\u003e128\u003c/span\u003e][\u003cspan citationid=\"CR129\" class=\"CitationRef\"\u003e129\u003c/span\u003e], La\u0026ndash;Sn [\u003cspan citationid=\"CR130\" class=\"CitationRef\"\u003e130\u003c/span\u003e][\u003cspan citationid=\"CR131\" class=\"CitationRef\"\u003e131\u003c/span\u003e], Ce\u0026ndash;Sn [\u003cspan citationid=\"CR132\" class=\"CitationRef\"\u003e132\u003c/span\u003e], Cr\u0026ndash;Sn [\u003cspan citationid=\"CR133\" class=\"CitationRef\"\u003e133\u003c/span\u003e] etc., Sn Alloyed with Electrochemically Active Metals: Ge-Sn [\u003cspan citationid=\"CR134\" class=\"CitationRef\"\u003e134\u003c/span\u003e][\u003cspan citationid=\"CR135\" class=\"CitationRef\"\u003e135\u003c/span\u003e][\u003cspan citationid=\"CR136\" class=\"CitationRef\"\u003e136\u003c/span\u003e], Sb\u0026ndash;Sn[\u003cspan citationid=\"CR137\" class=\"CitationRef\"\u003e137\u003c/span\u003e][\u003cspan citationid=\"CR138\" class=\"CitationRef\"\u003e138\u003c/span\u003e][\u003cspan citationid=\"CR139\" class=\"CitationRef\"\u003e139\u003c/span\u003e], Ag\u0026ndash;Sn [\u003cspan citationid=\"CR140\" class=\"CitationRef\"\u003e140\u003c/span\u003e][\u003cspan citationid=\"CR141\" class=\"CitationRef\"\u003e141\u003c/span\u003e], Mg\u0026ndash;Sn[\u003cspan citationid=\"CR142\" class=\"CitationRef\"\u003e142\u003c/span\u003e][\u003cspan citationid=\"CR143\" class=\"CitationRef\"\u003e143\u003c/span\u003e] etc. Overall, despite the actual progress of portable electronic products, the Sn-M alloy state-of-the-art anode performance still cannot meet advanced LIB requirements for electric vehicles or even grid-level energy storage, which is mainly due to its huge volume change leads to a bad life cycle.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The recent method of improving the electrochemical performance of Sn-M alloy is introducing electrical conductive hydrogels. Up to now, 3D CPHs have attracted attention due to their larger active surface area, shorter ion and electron transport pathways, and better adaptation to stress at the electrode.[\u003cspan citationid=\"CR144\" class=\"CitationRef\"\u003e144\u003c/span\u003e][\u003cspan citationid=\"CR145\" class=\"CitationRef\"\u003e145\u003c/span\u003e]. Some of which will be discussed below in detail.\u003c/p\u003e \u003cp\u003eXu et al., successfully prepared new three-dimensional (3D) polyaniline hydrogel-encapsulated SnCu nanotubes (PANI) (SnCu/PANI). The SnCu nanotubes and the in situ polymerized PANI hydrogel were coated and combined together, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a) [\u003cspan citationid=\"CR146\" class=\"CitationRef\"\u003e146\u003c/span\u003e]. The detailed morphology of Sn-Cu nanotubes anchored by PANI was characterized by SEM and TEM, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b) and (c). The superimposed SnCu nanotubes are uniformly dispersed in the PANI hydrogel matrix and fixed by it. The PANI network improves the conductivity of the composite material and prevents the electrode from cracking. The PANI hydrogel intersects the dispersed SnCu nanotubes as a whole, which plays a key role in avoiding direct contact between the SnCu nanotubes and the electrolyte and inhibiting the formation. The unstable SEI film on SnCu nanotubes contributes to excellent electrochemical performance. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (d) shows the constant current charge and discharge curve of the SnCu/PANI hydrogel at a current density of 0.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. SnCu/PANI initial discharge and charge capacities are 1332 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1034 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, which are much higher than commercial graphite anodes. In Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (e), the 3D SnCu/PANI hydrogel has a higher capacity than the SnCu nanotube electrode using PVDF as a binder. The former has a capacity of 552 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is higher than the 450 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of SnCu nanotubes after 300 cycles which is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (f). The constant current cycle curve is performed at 0.1 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. After 500 cycles, the capacity is 584 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This is because the porous PANI hydrogel helps to improve the electron transport of the electrode. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e(g) is the Nyquist diagram of SnCu/PANI hydrogel electrode. The low-frequency linear slope of is relatively large, indicating that the composite electrode has a faster lithium ion transmission rate, which is conducive to high rate charge/discharge.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eXu et al., successfully synthesized a unique coral-like 3D Sn-Cu/PANI/GO nanostructured electrode through a simple and scalable solution process [\u003cspan citationid=\"CR147\" class=\"CitationRef\"\u003e147\u003c/span\u003e] and the general synthesis procedure and detailed structure of the 3D Sn-Cu/PANI/GO hydrogels. The hydrogel is schematically illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a). In-situ coating of polymer layer on the surface of Sn-Cu NPs and GO nanoflames can provides electrical connection and maintains structural stability and inhibits Sn-Cu NPs aggregation to further improve electrochemical performance. The morphology and structural information of Sn-Cu/PANI/GO hydrogel electrodes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (b) respectively. The SEM image demonstrated the hierarchical porous nanostructured Sn-Cu/PANI hydrogel composite electrode. Furthermore, TEM showed that PANI formed a continuous network. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (d) and (e), a constant current charge/ discharge cycle of 2.0 to 0.01 V was used to evaluate the electrochemical performance of the composite electrode. The Sn-Cu/PANI/ GO hydrogel electrode exhibits improved electrochemical characteristics. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (d) demonstrates the result of the potential curve with an increase of 0.2 C. The first discharge / charge cycle provides a specific charge capacity of 1259 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a discharge capacity of 1466 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which corresponds to a coulombic efficiency of 85%. From cycle 30 to cycle 200, there is almost no change in the charge and discharge curves, indicating that the 3D Sn-Cu/ PANI/GO electrode is very stable during the cycle. Even after 200 cycles at a charge / discharge rate of 0.2 C, the composite can still provide a reversible specific capacity of 693 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (e). Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (f) shows the cycling performance of the three electrodes at a current density of 0.2 C. The Sn-Cu/PANI/GO electrode shows excellent cycle performance. This is due to the strong synergy between the 3D conductive network hydrogel and the NP Sn-Cu PANI coating. The coating can inhibit Sn-Cu NPs agglomeration into larger sized particles, which improving cycle stability. Finally, impedance measurement shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (g) shows, the GO and 3D porous structure effectively improve the conductivity of the electrode and reduce the contact resistance and charge transfer resistance, which helps to significantly improve reversible ability and speed ability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Transitional Metal Oxide (TMO) Based Hydrogels\u003c/h2\u003e \u003cp\u003eTMOs (MxOy, M\u0026thinsp;=\u0026thinsp;Fe, Co, Ni, Mn, Mo, Cr, Nb, etc.) are attractive candidates because their reversible capacity is about 2\u0026ndash;3 times higher than traditional graphite. [\u003cspan citationid=\"CR148\" class=\"CitationRef\"\u003e148\u003c/span\u003e], [\u003cspan citationid=\"CR149\" class=\"CitationRef\"\u003e149\u003c/span\u003e], [\u003cspan citationid=\"CR150\" class=\"CitationRef\"\u003e150\u003c/span\u003e], [\u003cspan citationid=\"CR151\" class=\"CitationRef\"\u003e151\u003c/span\u003e], [\u003cspan citationid=\"CR152\" class=\"CitationRef\"\u003e152\u003c/span\u003e][\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In particular, MO-type metal oxides have begun research work as LIB anodes [\u003cspan citationid=\"CR153\" class=\"CitationRef\"\u003e153\u003c/span\u003e], [\u003cspan citationid=\"CR154\" class=\"CitationRef\"\u003e154\u003c/span\u003e] because of their wide availability in nature, ease of synthesis procedures, and only moderate safety issues. Graphite, as well as eco-friendliness, corrosion resistance and decent cost economy.[\u003cspan citationid=\"CR148\" class=\"CitationRef\"\u003e148\u003c/span\u003e][\u003cspan citationid=\"CR149\" class=\"CitationRef\"\u003e149\u003c/span\u003e] [\u003cspan citationid=\"CR150\" class=\"CitationRef\"\u003e150\u003c/span\u003e][\u003cspan citationid=\"CR151\" class=\"CitationRef\"\u003e151\u003c/span\u003e][\u003cspan citationid=\"CR152\" class=\"CitationRef\"\u003e152\u003c/span\u003e][\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Several transition metal oxides such as TiO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR155\" class=\"CitationRef\"\u003e155\u003c/span\u003e], NiO [\u003cspan citationid=\"CR156\" class=\"CitationRef\"\u003e156\u003c/span\u003e], SnO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR157\" class=\"CitationRef\"\u003e157\u003c/span\u003e], Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [\u003cspan citationid=\"CR158\" class=\"CitationRef\"\u003e158\u003c/span\u003e], CuO [\u003cspan citationid=\"CR159\" class=\"CitationRef\"\u003e159\u003c/span\u003e], MoO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR160\" class=\"CitationRef\"\u003e160\u003c/span\u003e], Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR161\" class=\"CitationRef\"\u003e161\u003c/span\u003e][\u003cspan citationid=\"CR162\" class=\"CitationRef\"\u003e162\u003c/span\u003e][\u003cspan citationid=\"CR163\" class=\"CitationRef\"\u003e163\u003c/span\u003e], CoO [\u003cspan citationid=\"CR164\" class=\"CitationRef\"\u003e164\u003c/span\u003e] etc., have successfully tested as anodes for LIBs. However, its electrical conductivity is relatively poor and its volume changes greatly during Li\u003csup\u003e+\u003c/sup\u003e insertion and removal [\u003cspan citationid=\"CR165\" class=\"CitationRef\"\u003e165\u003c/span\u003e]. The large voltage difference between charge and discharge also leads to low energy efficiency. Therefore, it is still a huge challenge to manufacture high-performance transition metal oxide electrode materials with good cycle stability and speed performance. Several strategies have been developed to improve structural integrity and conductivity such as developing nanostructured TMOs: Co3O4 [\u003cspan citationid=\"CR163\" class=\"CitationRef\"\u003e163\u003c/span\u003e][\u003cspan citationid=\"CR161\" class=\"CitationRef\"\u003e161\u003c/span\u003e], CoO [\u003cspan citationid=\"CR166\" class=\"CitationRef\"\u003e166\u003c/span\u003e] Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [\u003cspan citationid=\"CR167\" class=\"CitationRef\"\u003e167\u003c/span\u003e][\u003cspan citationid=\"CR168\" class=\"CitationRef\"\u003e168\u003c/span\u003e], SnO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR169\" class=\"CitationRef\"\u003e169\u003c/span\u003e][\u003cspan citationid=\"CR170\" class=\"CitationRef\"\u003e170\u003c/span\u003e][\u003cspan citationid=\"CR171\" class=\"CitationRef\"\u003e171\u003c/span\u003e], TiO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR172\" class=\"CitationRef\"\u003e172\u003c/span\u003e], etc., TMOs with \u003cb\u003eporous structures\u003c/b\u003e: porous Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e microspheres [\u003cspan citationid=\"CR173\" class=\"CitationRef\"\u003e173\u003c/span\u003e], spherical mesoporous Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e particles [\u003cspan citationid=\"CR174\" class=\"CitationRef\"\u003e174\u003c/span\u003e], 1D mesoporous single-crystalline Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanobelts [\u003cspan citationid=\"CR175\" class=\"CitationRef\"\u003e175\u003c/span\u003e], porous Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanospheres[\u003cspan citationid=\"CR176\" class=\"CitationRef\"\u003e176\u003c/span\u003e], porous CoO nanostructure arrays on nickel foam[\u003cspan citationid=\"CR177\" class=\"CitationRef\"\u003e177\u003c/span\u003e], Mesoporous NiO microspheres [\u003cspan citationid=\"CR178\" class=\"CitationRef\"\u003e178\u003c/span\u003e], porous Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoplates [\u003cspan citationid=\"CR179\" class=\"CitationRef\"\u003e179\u003c/span\u003e] etc., TMOs with hollow structures: hollow Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e spheres via a simple template-free [\u003cspan citationid=\"CR180\" class=\"CitationRef\"\u003e180\u003c/span\u003e], multi-shelled Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e hollow microspheres [\u003cspan citationid=\"CR181\" class=\"CitationRef\"\u003e181\u003c/span\u003e], Hollow Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanospheres [\u003cspan citationid=\"CR182\" class=\"CitationRef\"\u003e182\u003c/span\u003e], hollow nanospheres of MnO\u003csub\u003e2\u003c/sub\u003e, Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and MnO [\u003cspan citationid=\"CR183\" class=\"CitationRef\"\u003e183\u003c/span\u003e] etc., TMOs based hybrid nanostructured composites: carbon-coated Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e hollow particles [\u003cspan citationid=\"CR184\" class=\"CitationRef\"\u003e184\u003c/span\u003e], carbon-coated Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanorods [\u003cspan citationid=\"CR185\" class=\"CitationRef\"\u003e185\u003c/span\u003e], mesoporous CoO nanorod@carbon nanotube[\u003cspan citationid=\"CR186\" class=\"CitationRef\"\u003e186\u003c/span\u003e], 1D Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e/carbon nanowires[\u003cspan citationid=\"CR187\" class=\"CitationRef\"\u003e187\u003c/span\u003e], 2D Fe3O4/carbon nanosheets [\u003cspan citationid=\"CR188\" class=\"CitationRef\"\u003e188\u003c/span\u003e], 3D macroporous Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e/carbon nanospheres [\u003cspan citationid=\"CR189\" class=\"CitationRef\"\u003e189\u003c/span\u003e], Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanorods/carbon nanofibers composite[\u003cspan citationid=\"CR190\" class=\"CitationRef\"\u003e190\u003c/span\u003e] and graphene-wrapped Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e[\u003cspan citationid=\"CR191\" class=\"CitationRef\"\u003e191\u003c/span\u003e], MnO [\u003cspan citationid=\"CR192\" class=\"CitationRef\"\u003e192\u003c/span\u003e], Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e[\u003cspan citationid=\"CR193\" class=\"CitationRef\"\u003e193\u003c/span\u003e], Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR194\" class=\"CitationRef\"\u003e194\u003c/span\u003e], and CoO [\u003cspan citationid=\"CR195\" class=\"CitationRef\"\u003e195\u003c/span\u003e] etc., developing Binary metal oxides: NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR196\" class=\"CitationRef\"\u003e196\u003c/span\u003e][\u003cspan citationid=\"CR197\" class=\"CitationRef\"\u003e197\u003c/span\u003e][\u003cspan citationid=\"CR198\" class=\"CitationRef\"\u003e198\u003c/span\u003e], ZnCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e[\u003cspan citationid=\"CR199\" class=\"CitationRef\"\u003e199\u003c/span\u003e], MnCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR200\" class=\"CitationRef\"\u003e200\u003c/span\u003e], and CoMn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e[\u003cspan citationid=\"CR200\" class=\"CitationRef\"\u003e200\u003c/span\u003e] etc. However, during lithium ion intercalation/deintercalation, severe aggregations and large volume changes of nanoparticles have been observed [\u003cspan citationid=\"CR201\" class=\"CitationRef\"\u003e201\u003c/span\u003e], which limits their application in energy storage systems. Recently, 3D graphene such as hydrogel conductive foams, gels and networks, with its high specific surface area, adequate networks, good conductivity and multidimensional electron transport, has launched new research as a cornerstone of building new 3D networked conductive hydrogels[\u003cspan citationid=\"CR202\" class=\"CitationRef\"\u003e202\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eZhou et al., prepared a new type of 3D Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/rGO hydrogel (FGH) through simple hydrothermal strategy. [\u003cspan citationid=\"CR203\" class=\"CitationRef\"\u003e203\u003c/span\u003e]. In this hydrogel, rGO sheets self-assemble into an interconnected macroporous structure, and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes are encapsulated in the rGO layer, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e(a). The SEM image of FGH shows a well-defined and interconnected 3D porous network with pore sizes ranging from submicron to several microns, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (b and c). This indicates that the Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes in FGH are considered to be enveloped within the pore wall composed of thin stacked layers of RGO sheets. TEM observations further confirmed the uniform distribution of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes in rGO sheet in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (d). In Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (e), we can see the electrochemical performance of the electrode, FGH exhibited a discharge curve similar to Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes in the first cycle, with a discharge slope 0.75 V between approximately 1.29 V and 0.78 V. When cycling at 200 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the specific capacity of the Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes is significantly attenuated and after 70 cycles it only maintains 63.5 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In the case of FGH, although its first discharge capacity (1009.1 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is slightly lower than that of pure Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes (1147.4 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), it shows better cycle performance, stabilizing at ~\u0026thinsp;700 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (f). Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (g) compares the nanotube velocity performance of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and FGH at different current densities. For FGH, reversible capacities of 850, 780, 550, 400, and 280 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were obtained at current densities of 200, 400, 600, 800, and 1000 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which significantly exceeded Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes (for example, ~ 100 and 60 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 200 and 400 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively). When the current density returns to 200 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, FGH can still provide a capacity of up to ~\u0026thinsp;600 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which means its structure is stable and reversible. The AC impedance spectra of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and FGH nanotubes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e(h). The Nyquist diagram is composed of concave semicircles in the high and mid-frequency regions and straight lines in the low-frequency regions. The result shows that the charge transfer of FGH (16.5 Ω) is lower than that of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanotubes (73.5 Ω), indicating that a good conductive network is formed due to the incorporation of scales 3D rGO.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBao et al., fabricated a hybrid hydrogel system based on CNTs and CP lattices, which was loaded with TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles to enhance its electrode capabilities in advanced LIB [\u003cspan citationid=\"CR204\" class=\"CitationRef\"\u003e204\u003c/span\u003e]. The fabrication process is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea. First prepare a homogeneous solution containing PEDOT nanoparticles: water-soluble PSS, CNT and TiO\u003csub\u003e2\u003c/sub\u003e are well dispersed, and then gelling agent is inserted for hydrogel formation, and it can be peeled off as a separate film and cut into hydrogels of different sizes and shapes. The hydrogel is polymerized in-situ to form an interconnected 3D structure, where the CNT is essential to ensure mechanical strength and flexibility. PEDOT: PSS is responsible for the effective transport of delocalized electrons to obtain high conductivity; TiO\u003csub\u003e2\u003c/sub\u003e is selected to achieve high capacity, conductivity and electrochemical stability. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb, CNTs penetrate the entire structure, while TiO\u003csub\u003e2\u003c/sub\u003e NPs form embedded clusters in the matrix. This network provides the TiO\u003csub\u003e2\u003c/sub\u003e/PEDOT:PSS/CNT electrode with excellent electrical performance, even after 500 repeated bends at a radius of 3.5 mm. The TiO\u003csub\u003e2\u003c/sub\u003e/PEDOT:PSS/CNT electrode shows a higher charge storage capacity in 4000 seconds of charge/discharge, reaching 76 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e compared with the TiO\u003csub\u003e2\u003c/sub\u003e electrode made of polyvinylidene fluoride binder. In addition, the hydrogel system loaded with TiO\u003csub\u003e2\u003c/sub\u003e showed a high area capacity of 2.2 mAhcm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e at a rate of 0.1C (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ec and \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ed). By combining ideal anode or cathode active materials with CNTs CPHs hybrid systems, batteries with improved mechanical properties and hence electrochemical properties, can be easily manufactured.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e3D hydrogels rGO anchored in ultrafine CoO NPs (CoO/rGO nanocomposites) was synthesized using a simple hydrothermal strategy and post-heat treatment process. [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]. Small sized CoO NPs encapsulated in the hole structure are fixed on rGO nanosheets for CoO/rGO nanocomposites, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e(a). The SEM and TEM images showed that partial overlap or fusion of the flexible RGO nanomembrane resulted in the formation of physical cross-linking sites in the 3D framework shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e(b) and (c), respectively. It also shows that the high density CoO NPs are uniformly dispersed on the surface of the 3D rGO nano-sheets, with wrinkled and wavy structures, and there is no aggregation of CoO nanoparticles in the CoO/rGO nanocomposites. Electrochemical performance was evaluated by using coin-type batteries. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e (d) shows that the CoO/rGO nanocomposite charge-discharge curve exhibits a long and extended potential plateau during the first charge/discharge process. The curve is symmetrical in shape, indicating that Li\u003csup\u003e+\u003c/sup\u003e insertion/removal is highly reversible under different current densities. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e (e) shows that the CoO/rGO nanocomposite maintains high specific capacities of 890.2, 690.4, 543.8, and 457.0 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, even at 200, 800, 1600, and 2400 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. When the current returns to 100 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the capacity increases to 1025.8 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 82 cycles. CoO NPs and rGO nano-sheets show poor speed capabilities. After cycling 82 times at different current densities, the capacities of CoO NPs and rGO nanosheets were 676.3 and 240.6 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 100 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. Therefore, the retention capacity of the nanocomposite CoO/rGO is better than the other two electrode materials, which is attributed to the well-designed structure with three-dimensional rGO nanosheets. The remaining oxygen-containing functional groups in the graphene nanomembrane after hydrothermal treatment facilitate the formation of covalent forces between the oxide and the matrix, and the large number of pore structures in Li can effectively limit the serious volume change Li\u003csup\u003e+\u003c/sup\u003e insertion/extraction process of CoO nanoparticles. Then the 3D CoO/rGO nanocomposite showed excellent cycle performance and speed capability. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e (f) displays the impedance spectra of CoO NPs and CoO/rGO nanocomposites at a potential of 3.0 V after four cycles. The Nyquist diagram is composed of concave semicircles in the high and mid-frequency regions and straight lines in the low-frequency regions. According to the fitting results, the charge transfer of CoO/rGO (45.4) nanocomposites is slightly lower than that of CoO (112.8) nanoparticles, indicating that a good conductive network is formed due to the introduction of rGO three-dimensional nanosheets.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eShaijumon, and others [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] have produced a 3D structure based on reduced graphene oxide (rGO), which has a unique flower-like CoO microstructure, uniformly embedded in the graphene hydrogel matrix (CoO-GHG), thus forming a complete interconnection. shown in Fig.\u0026nbsp;13 (a). 2]. CoO-GHG exhibits a 3D interconnection structure, with CoO flowers embedded in the 3D graphene lattice, as indicated in Fig.\u0026nbsp;13 (b), and the TEM image in Fig.\u0026nbsp;14 (c) shows that the CoO flakes they are embedded in the graphene matrix. The electrochemical activities of CaO and CoO-GHG are shown in Fig.\u0026nbsp;13 (d) and (e), respectively. The constant current charge/ discharge voltage curves of the CoO-GHG and CoO electrodes cycle Li/Li\u003csup\u003e+\u003c/sup\u003e in a voltage window of 0.01-3.0 V at a current rate of 100 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The initial discharge capacities of CoO-GHG and CoO electrodes were 1230 and 1020 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, indicating that the irreversible loss of capacity of the respective electrodes was 20% and 27%. Interestingly, the first discharge capacity obtained by the two electrodes is much higher than the theoretical CoO capacity (\u0026asymp;\u0026thinsp;715 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and the higher original CoO capacity after 50 cycles is the result of reversible formation. The CoO-GHG electrode exhibits improved cycle stability, as indicated in Fig.\u0026nbsp;13 (f), with a very high reversible capacity of 1010 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and cycles in excess of 100 at a current density of 100 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e times. However, the original CoO electrode showed rather poor cycling performance and its capacity dropped sharply during cycling (Fig.\u0026nbsp;14 (g), at the same current density of 100 mA g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. 0020, 370 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was recorded in 100 cycles reversible capacity) Compared with the original CoO electrode, the CoO-GHG electrode has excellent cyclic behavior, which can be attributed to the 3D graphene hydrogel lattice. To further evaluate the excellent electrochemical performance of the CoO-GHG electrode relative to CoO, the velocity performance study tested the two electrodes by cycling at different current rates, namely 100, 200, 400, 800, 1600 and 3200 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;13b). At current speed, the capacity is about 300mAh g-1. Under the current of 1600 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, CoO-GHG shows superior speed performance. Compared with the original CoO electrode, it can only hold\u0026thinsp;\u0026asymp;\u0026thinsp;50 at the same current rate. mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Additionally, in the final 100 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e cycle, the CoO-GHG electrode maintained a capacity of 800 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, while the original CoO electrode was only able to provide a capacity of 410 mAhg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which indicates the kinetics of the CoO-GHG sample is better than that of the original CoO. It's worth noting that the CoO-GHG electrode achieves high-speed performance without adding additional conductive carbon. This clearly shows that the graphene sheets in the CoO-GHG 3D interconnect network improve conductivity. The synergistic effect of the high conductivity rGO network and the unique flower-shaped morphology of CoO results in an electrochemical performance of the CoO-GHG electrode superior than the original CoO electrode.\u003c/p\u003e \u003cp\u003eCoO and CoO-GHG electrodes are cycled at different rates from 100 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 3200 mAg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eWe emphasized how to make hydrogels and integrate them into the LIB active materials, and we provide interesting examples to demonstrate the versatility of hydrogels made from conductive polymers and carbon materials. The creative and combined methods used in the design of functional hydrogels are expected to continue to produce materials with great potential in the field of energy storage. Specifically, a fascinating strategy is to combine CPs or graphene/CNTs with hydrogel electrodes to increase energy storage and power density production; Similarly, combine TMOs and alloys with the conductive hydraulic glue mix. Obtaining the most suitable cycle stability provides a fascinating technique; increasing surface area, porosity, and creating well-connected channels in the form of a hydrogel to promote electron transfer and ion diffusion are expected to improve the electrochemical performance of the battery. Although this article discusses these achievements, ECH development in energy storage systems is still in its early stages. Before transferring high-performance general-purpose ECH to sensitive applications, their manufacturing still faces huge scientific and technological challenges. Compared with typical electrodes, the active materials in LIB electrodes made of ECH have more complex structures and more complex shapes, as well as more complex special elements. These include: (1) The porous hydrogel scaffold provides a huge internal space for the dramatic volume changes of high-energy electrochemical nanoparticles; (2) The uninterrupted conductive community promotes efficient and rapid electron and ion transfer methods; (3) ) The interlocking and interlocking polymer matrix ensures excellent mechanical strength. Looking ahead, continuing to improve CPH performance in exciting energy storage applications requires better control of its electrical, electrochemical, thermal and mechanical properties, as well as chemical and surface functionalization. The development of CH-based materials to synergize the advantages of various components is another future promising approach. At the same time, understand the basic knowledge of CH more deeply, advanced modeling and simulation research is needed. The most advanced microscopy and spectroscopy measurements are also needed to study the basic electrochemistry of nanostructured CHs and the electrochemical dynamics of the mixed inorganic-organic interface. These studies will provide more information on how to make full use of CHs to optimize the electrochemical performance of energy storage devices.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZhang J, Yu A (2015) Nanostructured transition metal oxides as advanced anodes for lithium-ion batteries. 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All of these must be sustainable electrochemically and generally robust. The main limitation in recognizing these functions is the lack of electrodes with excellent mechanical and electrochemical properties. CHs combine the electrical conductive properties of metals or semiconductors with the unique properties of hydrogels and are important for forming and assembling lithium ion battery electrodes. Which can contain a large amount of electrolyte solution in the conductive network of 3D nanostructures, providing a large number of sites on the surface for the required electrochemical reactions. Until now, 3D nanostructured CH has shown excellent performance when used as an electrode materials for LIBs. Future efforts are based on improving the intentional CH with controllable size, composition, shape, and interface. In this review, we focus on fabrication of CH, how conductive hydrogels are incorporated into the active materials (Si nanparticles, tin-metal alloy and transition metal oxides) of LIBs, and show some of the hydrogel electrode materials in LIBs based on Si, tin alloys and transition metal oxides based hydrogels.\u003c/p\u003e","manuscriptTitle":"Development of Conductive Hydrogel-Based Anode Materials for Lithium-Ion Batteries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-03 13:59:16","doi":"10.21203/rs.3.rs-5548724/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e8d07710-270d-4bf1-8d0f-1674a5e493dc","owner":[],"postedDate":"December 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":40938218,"name":"Electrochemistry"}],"tags":[],"updatedAt":"2024-12-03T13:59:16+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-03 13:59:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5548724","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5548724","identity":"rs-5548724","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}