11pt, fleqn, a4paper, ]LegrandOrangeBook Cationic Synergy Engineering by Tuning Co/Mn Ratio for Optimizing Supercapacitors Performance

11pt, fleqn, a4paper, ]LegrandOrangeBook Cationic Synergy Engineering by Tuning Co/Mn Ratio for Optimizing Supercapacitors Performance | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 24 June 2025 V1 Latest version Share on 11pt, fleqn, a4paper, ]LegrandOrangeBook Cationic Synergy Engineering by Tuning Co/Mn Ratio for Optimizing Supercapacitors Performance Authors : Wenwen Kong , Xin Liu , Tianhui Wu [email protected] , Yang Zhao , Jie Guan , Nianrui Qu , Jianmin Gu , and Desong Wang Authors Info & Affiliations https://doi.org/10.22541/au.175073238.85412300/v1 156 views 100 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract 11pt, fleqn, a4paper, ]LegrandOrangeBook The design of high-performance and cost-effective electrode materials for supercapacitors is attracting growing interest. Current research efforts focus predominantly on surface-level modifications such as foreign metal/anion doping to augment active sites and structural porosity, while intrinsic material engineering via compositional and crystallographic tailoring remains underexplored, despite its potential to fundamentally tune charge storage mechanisms. Here, based on the excellent properties of bimetallic bases (Mn and Co), we have synthesized a series of Co-doped Mn-based compounds with adjustable morphology and crystal phase by a simple hydrothermal method, in which the supercapacitor performance exhibits a trend of initial enhancement followed by degradation with the addition of Co 2+ . Particularly, the sample of doping 60 mol% Co 2+ concentration exhibits exceptional charge storage characteristics, delivering the specific capacitance of 308 F·g -1 at 0.2 A·g -1 , attributed to the optimal synergistic effects originating from the maximum ratio of Co 3+ /Co 2+ , which would offer an effective approach to enhance the electrochemical properties of transition metal oxides by systematically investigating the composition-structure-performance relationships. Cationic Synergy Engineering by Tuning Co/Mn Ratio for Optimizing Supercapacitors Performance Wenwen Kong, 1,‡ Xin Liu, 1,‡ Tianhui Wu, 1, *, Yang Zhao, 1 Jie Guan, 1 Nianrui Qu, 1 Jianmin Gu, 1, * Desong Wang 1,2, * 1 State Key Laboratory of Metastable Materials Science and Technology (MMST), Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004, China E-mail: [email protected] ; [email protected] ; [email protected] 2 School of Sciences, Hebei University of Science and Technology, Shijiazhuang 050018, P. R. China. E-mail: [email protected] math_shortcuts ‡ Wenwen Kong and Xin Liu contributed equally to this work. KEYWORDS: supercapacitors; manganese oxide; cobalt doping; electrochemical properties math_shortcuts 11pt, fleqn, a4paper, ]LegrandOrangeBook ABSTRACT: The design of high-performance and cost-effective electrode materials for supercapacitors is attracting growing interest. Current research efforts focus predominantly on surface-level modifications such as foreign metal/anion doping to augment active sites and structural porosity, while intrinsic material engineering via compositional and crystallographic tailoring remains underexplored, despite its potential to fundamentally tune charge storage mechanisms. Here, based on the excellent properties of bimetallic bases (Mn and Co), we have synthesized a series of Co-doped Mn-based compounds with adjustable morphology and crystal phase by a simple hydrothermal method, in which the supercapacitor performance exhibits a trend of initial enhancement followed by degradation with the addition of Co 2+ . Particularly , the sample of doping 60 mol% Co 2+ concentration exhibits exceptional charge storage characteristics, delivering the specific capacitance of 308 F·g -1 at 0.2 A·g -1 , attributed to the optimal synergistic effects originating from the maximum ratio of Co 3+ /Co 2+ , which would offer an effective approach to enhance the electrochemical properties of transition metal oxides by systematically investigating the composition-structure-performance relationships. INTRODUCTION Advanced efficiency electrical energy storage (EES) technology is urgently needed to fully harness regenerative and sustainable energy sources. [1-5] Supercapacitors have garnered substantial research attention in last several years due to their exceptional power density, extended cycle stability, and rapid charge/discharge characteristics. [6-9] The electric double layer capacitance (EDLC) devices, [10, 11] as commercially available supercapacitors, deliver excellent cyclic performance and high reversibility, yet their development is hindered by low energy density. This intrinsic limitation has driven the emergence of pseudocapacitive materials or battery-like electrodes, whose architectures strategically integrate EDLC electrodes with redox-active counterparts. [12-15] Unlike the purely physical charge adsorption mechanism of EDLC, these materials relies on redox reaction at the electrode surface or quasi-surface in a faradaic process, [16] involving the insertion and de-insertion of electrolyte ions at the electrode-electrolyte interface, [17, 18] To achieve high-performance charge storage of pseudocapacitive or battery-like electrodes, electrode materials should meet the following criteria: (i) high-active redox sites, (ii) optimizing the electron conduction and ion diffusion path, (iii) ensuring structural stability. Transition metal oxides are widely utilized in supercapacitor applications given their economic feasibility, abundant resource availability, and superior charge storage capabilities. [19] Compared to single transition metal components, the bimetallic compounds with more abundant redox reaction sites, are recognized as potential electrode materials, in which the different proportions of cations largely determine the physical and chemical properties of the materials, especially for stoichiometric tuning. [20-22] Doping strategies are able to regulate the electronic structure and active site of materials by introducing heterogeneous atoms, which have become an efficient path to improve electrode performance. Tang et al. [23] synthesized the Mo-doped NiSe electrode materials with a capacity of 799.90 C·g -1 , as well as retaining its 90% original capacity after 8000 cycles. Thalji et al. [24] fabricated cobalt-doped tungsten suboxide used for electrode material, achieving the specific capacity of 792 F · g -1 . Doping strategies have made significant progress in enhancing charge storage properties, but establishing quantitative composition-structure-performance relationships remains essential for bimetallic oxide systems. Precise manipulation of transition metal cation ratios in bimetallic compounds becomes a viable methodology to investigate these correlations in supercapacitors. [25-27] Due to the distinct abilities for Co-based material (battery-type characteristics and cycling stability) and Mn-based material (pseudocapacitive behavior with high theoretical capacity), [28-30] Co-Mn bimetallic system serves as an ideal platform to study the underlying reaction mechanisms and structure-property relationships via precise control the ratio of Co and Mn cations. Their binary synergy has been demonstrated to enhance the electrochemical performance through synergistic electronic coupling [31, 32] , yet the underlying reaction mechanisms and structure-property relationships in these bimetallic systems remain insufficiently understood. Therefore, it is imperative to establish quantitative correlations between the composition of Co-Mn compound electrode materials and the supercapacitors electrochemical properties based upon an efficient and controllable synthesis method. In this work, we constructed a series of Co-doped Mn-based composites with various nanostructures via a hydrothermal method, achieving the crystalline phase regulation from the square crystal phase component to the cubic crystal phase and finally to the hexagonal crystal phase with the doping of Co ions, in which the supercapacitor performance shows a trend of initial enhancement followed by degradation . In particular, the 60 mol% Co-doped Mn 3-x Co x O 4 exhibits the highest specific capacity, reaching 308 F · g -1 at 0.2 A · g -1 , originating from the optimal synergistic effects in compounds with the highest Co 3+ /Co 2+ ratio . This systematic investigation elucidates the composition-structure-property relationships in transition metal oxides, establishing a rational dopant engineering framework for optimizing charge storage mechanisms and electrochemical performance in high-performance electrode design. EXPERIMENTAL SECTION Reagents. MnCl 2 ·2H 2 O (99.99%, Xiya Reagent), KOH (wt 98%, Sinopharm Chemical Reagent) and CoCl 2 (99.5%, Xiya Reagent) were obtained from commercial sources and used directly. Preparation of Mn-Co composites. In a typical experiment, 8 mmol of manganese chloride dihydrate (MnCl 2 ·2H 2 O) was firstly dissolved in 5 ml distilled water, and magnetically stirred for five minutes to obtain a homogenous solution, and 30 mmol of potassium hydroxide (KOH) was put in ten ml ultrapure water to obtain a transparent solution. Subsequently, the above two kinds of solutions were gradually combined under continuous magnetic stirring and agitated for 15 minutes. Then the obtained solution was transferred into a p polytetrafluoroethylene-lined stainless-steel autoclave, sealed, and subsequently heated at 200 °C for 12 hours. After cooling to room temperature, the precipitation was separated via three cycles of centrifugation and washing, followed by drying overnight in an 80 °C air oven. The Co-Mn composites were obtained under the same conditions by Co 2+ (CoCl 2 ) replacing part of Mn 2+ according to a certain molar ratio (10%, 20%, 30%, and up to 100%), correspondingly labeled Co-Mn-10, Co-Mn-20, up to Co-Mn-100. Materials characterization. Transmission electron microscopy (TEM) images were recorded on a JEM-2100F transmission electron microscope. Scanning electron microscopy (SEM) images were received by employing a Hitachi S4800 field-emission scanning electron microscope. X-ray powder diffraction (XRD) patterns of the samples were obtained by Cu Kα radiation using a Bruker AXS D8 diffractometer. And the X-ray photoelectron spectroscopy (XPS) determination was carried out using ESCALab220I-XL. Electrochemical measurements. Electrochemical performance measurements were conducted at a 1208C electrochemical workstation (Solartron Analytical, UK), equipped with a three-electrode cell. The Hg/HgO electrode and the platinum sheet were used as reference electrode and counter electrode, respectively. The working electrode was prepared as follows: the slurry mixture of electroactive materials, acetylene black and polytetrafluoroethylene was coated on the nickel foam in the ratio of 7.5: 1.5: 1, and pressed into the flake and dried at 80 °C for 12 hours at 10 Mp. The galvanostatic charge-discharge (GCD) tests were contucted on the LANHE CT2001A battery tester, and the cut-off voltage window was 0 to 0.5 V vs. Hg/HgO. The electrochemical impedance spectroscopy (EIS) measurements were carried out within the range of 20000 Hz to 0.01 Hz, and the signal amplitude was 5 mV. All electrochemical measurements were performed in 3 M KOH aqueous electrolyte solution at room temperature. RESULTS AND DISCUSSION The ideal supercapacitor materials should possess high theoretical specific capacitance, superior electrochemical activity, excellent electrical conductivity, and other desirable characteristics. Compared with single-component oxides, multi-metal oxide systems demonstrate synergistic enhancements in charge storage performance through improved electrical conduction, elevated reversible capacity, and prolonged cycling durability. [33, 34] The Mn-based compounds possess a variety of oxidation valences, high theoretical specific capacitance, [35-37] and the Co-based compounds have superior redox properties, [38, 39] thus, the Mn-based and Co-based compounds are selected as ideal active material for the synthesis of homogeneous nanoscale Mn-Co oxide electrode materials. By manipulating the concentrations of doping Co 2+ ions in Mn-based compounds, a series of Co-Mn composites with various polymorphisms can be obtained with the doped Co 2+ content from 0 to 100 mol%, which offer a model system for studying the bimetallic-based composition-structure-performance correlations in supercapacitor. The samples of Mn 3-x Co x O 4 were synthesized with a facile and feasible hydrothermal method, in which structures (including the crystal phase and shape), could be contemporaneously modified through controlling the concentrations of the doped Co 2+ into the Mn-based compounds (Figure 1). The composition and structure characterizations of the Mn 3-x Co x O 4 samples were determined by X-ray diffraction (XRD) (Figures 1 and S1). Without the addition of Co 2+ ions, the pattern of pure Mn 3-x Co x O 4 sample (Co-Mn-0) could be indexed as tetragonal phase (JCPDS No. 80-0382), where the diffraction peak located at 32.38° is the typical characteristic peak of the tetragonal phase, corresponding to the (103) crystal plane. As the concentration of Co 2+ rose to 50 mol%, although the patterns still remained in the tetragonal phase, the intensity of the characteristic peak gradually decreased. Along with the continuous increase of Co 2+ concentration, it was noted that the transition from tetragonal to cubic structure became evident. Particularly, when the Co 2+ ion concentration reached 60 mol% (Co-Mn-60), a completely cubic phase material (JCPDS No.74-1656) appeared. With the concentration of Co 2+ ion further increasing into the 100 mol%, the entire change from the cubic phase to the hexagonal phase occurred (JCPDS No. 45-0031). math_shortcuts Figure 1. (a) XRD patterns of the Co-Mn composites of Co-Mn-0, Co-Mn-10, Co-Mn-50, Co-Mn-60, Co-Mn-90 and Co-Mn-100, respectively. (b) Phase transformation in Mn-Co composites structures by Co 2+ doping. (c) The photographs of obvious change of precipitation samples obtained from different Co 2+ content. The structure properties for all the samples were characterized with SEM and TEM (Figures 2, S2 and S3). Without additional Co 2+ ions added, the SEM image of Co-Mn-0 exhibits uniform and glossy morphologies with a diameter of 3-4 μm (Figure 2a). As the concentration of Co 2+ increases, a trend of decreasing nanocrystal size is observed, reducing to approximately 2 μm when the Co 2+ concentration reaches 30 mol% (Figure 2b). With the further increase of concentration of Co 2+ from 40 to 70 mol%, a number of small hexagonal nanosheets begin to appear on the surface of the large-scale nanoprisms (Figure 2c). It is noteworthy that the small hexagonal nanosheets formed at the concentration of 60 mol% Co 2+ , exhibit a hollow structure characteristic (Figure 2d). When the Co 2+ concentration increases to between 80 and 100 mol%, the particle size increases significantly to 3-4 μm, which still maintains the hexagonal nanocrystal morphology (Figure 2e). Furthermore, the microstructures of as-prepared samples were further characterized by TEM (Figures 2f-h and S3), which demonstrate that the dimension of the nanosheets decreased by degrees as the concentration of the Co 2+ increases from 0 to 50 mol% (Figure 2f). Notably, the small hexagonal nanosheets are converted into nanorings when the concentration of Co 2+ reaches approximately 60 mol% (Figure 2g). Upon increasing the concentration of the Co 2+ further to 100 mol%, the dimensions of the nanosheets gradually increase again (Figure 2h). In addition, electron diffraction techniques verified the single-crystallinity features in all observed samples with clear lattice fringes, corresponding to the expected lattice planes (Insets of Figure 2f and h). [40] Figure 2. (a-e) SEM images of Co-Mn-0, Co-Mn-30, Co-Mn-40, Co-Mn-60, and Co-Mn-100. The scale bars are 2 μm, and the scale bars for insets of c and d are 500 nm. (f-h) TEM images of the sample Co-Mn-0, Co-Mn-60, Co-Mn-100. The scale bars are 1 μm, 160 nm, and 1 μm, respectively, and the insets of the f and h are the SAED pattern for the hexagonal plate. Figure 3. Electrochemical performance of Co-Mn-0, Co-Mn-40, Co-Mn-60, Co-Mn-80, and Co-Mn-100. (a) CV curves at 0.2 A · g -1 . (b) GCD at 0.2 A · g -1 . (c) Specific capacities at different current densities. (d) EIS spectra in Nyquist plots. (e) The relationship between the specifical capacitance and the Co 2+ ions doping content. The error bars represent the standard deviations of three repeated measurements. (f) Cycling stability of the at 1 A · g -1 . To evaluate electrochemical properties of Mn 3-x Co x O 4 electrode, the electrochemical tests were conducted in a three-electrode system in 3 M KOH aqueous electrolyte, with Hg/HgO and Pt as the reference electrode and counter electrode (Figure 3). The cyclic voltammetry (CV) tests have been conducted for the samples at scan rates from 2 to 30 mV · s -1 (Figures 3a and S4). All the CV curves show strong redox peaks rather than quasi-rectangular shapes at the potential window of -0.2~0.7 V (vs. Hg/HgO), representing that charge storage is mainly governed by the pseudocapacitive capacitance. [41] Furthermore, the CV curve of Co-Mn-60 displays a larger integrated area with a higher current density peak than the undoped Co 2+ and the other ratios of Co-doped Mn 3-x Co x O 4 samples (Figure 3a), suggesting that Co-Mn-60 possesses the highest specific capacitance. The GCD curves of the prepared samples at 0.2 A·g -1 were illustrated in Figures 3b and S5, indicating the reversible nature of the mixed oxide electrodes, and the specific capacitance derived from these plots could be calculated from GCD curves using the following equation: [42] \(\mathbf{C}=\frac{\mathbf{I}\ \mathrm{\Delta}\mathbf{t}}{\mathbf{m}\ \mathrm{\Delta}\mathbf{V}}\)(1) In the formula, m represents the mass of active substance (mg), I represents the current (A·g -1 ), ∆t represents the charge and discharge time (s), and ∆V represents the potential window (V). Obviously, Co-Mn-60 delivers the highest specific capacity of 308 F·g -1 at 0.2 A·g -1 , which is preferable to the other Co 2+ ion doped Mn 3-x Co x O 4 . The samples capacitance decreases slowly with the increase of current densities, which retains ~90% of the initial capacitance (Figure 3c). The maximum specific capacitance of Co-Mn-60 was 308 F·g -1 at 0.2·A·g -1 , and remained at 262 F·g -1 even at a higher current density of 10 A·g -1 In order to optimize the electrochemical properties of the materials, the effect of the different Co 2+ concentrations on the Nyquist plots of the EIS spectra for the composites was further analyzed (Figures 3d and S6). The impedance spectra exhibit a characteristic pattern consisting of two distinct regions, in which a well-defined semicircular arc in the high-frequency domain corresponds to the charge-transfer resistance (R ct ) associated with Faradaic processes at the electrode-electrolyte interface, and a linear Warburg-like response in the low-frequency region indicates the diffusion of ions in the electrode materials. [26] Notably, the R ct value of the Co-doped material is much lower than the undoped one (Figure 3d), and the increase of Co 2+ content has a minimal effect on the charge-transfer resistance changes. The influence of the Co 2+ doping amount on the electrochemical property was further investigated by analyzing the specific capacitance and cycle life of the Mn 3-x Co x O 4 . The dependence of charge storage capacity on Co 2+ dopant levels is systematically demonstrated in Figure 3e. The capacitive performance was improved with the increase of Co 2+ content before the Co 2+ concentration reached 60 mol%, and then gradually decreased upon further increasing in Co 2+ doping. Specifically, the highest specific capacitance was obtained at 60 mol% Co 2+ concentration, up to 308 F·g −1 (Table S1 and Figure S7). In addition, all Mn 3-x Co x O 4 samples with varying Co 2+ doping concentrations also demonstrated significantly improved cycling stability (Figure 3f), retaining approximately 90% of their initial capacitance even after 5,000 cycles. It can be seen that the Co-Mn-60 has a superior cyclic property over 95% capacitance retention rate. Figure 4. XPS spectra showing peaks corresponding to (a) Mn 2p regions of the samples Co-Mn-0, Co-Mn-10, Co-Mn-50, Co-Mn-60, Co-Mn-90. (b-c) Co 2p regions and O 1s regions of the samples Co-Mn-0, Co-Mn-50, Co-Mn-60, Co-Mn-90, and Co-Mn-100. (d) Surface ratios of Co and Mn chemical states from the XPS analysis. The capacitive performance of material is not only determined by its intrinsic crystal structure and surface morphology, but also closely related to the chemical state and composition during the reaction process. Therefore, X-ray photoelectron spectroscopy (XPS) was employed to further investigate the valence state information of Mn 3-x Co x O 4 (Figures 4, S8, and S9). The high-resolution XPS spectra of Mn 3-x Co x O 4 composite in the absence of Co 2+ ion shows four distinct peaks with binding energies of 640.7 eV (652.5 eV) and 642.6 eV (653.5eV) in the Mn 2p region (Figure 4a), corresponding to Mn 2+ and Mn 3+ respectively, [43, 44] which indicate the pristine sample is a composite of MnO and Mn 2 O 3 , in accordance with the XRD analysis of samples without Co 2+ addition (Figure 1). With the increase of Co 2+ , the positions of Mn 2+ and Mn 3+ exhibit a slight shift, but the spin-orbit splitting width (Δ=11.8 eV) remains unchanged, consistent with previous reports [45-47] . Concurrently, the emergence of a new valence state, Mn 4+ , is observed, indicating that the oxidation state of Mn in the composite material changes with the addition of Co 2+ (Figure S8). The Co 2p spectra reveal two prominent sets of peaks associated with Co 2+ (Co 2p 3/2 at 779.97 eV) and Co 3+ (Co 2p 3/2 at 781.57 eV) (Figures 4b and S8), [48-50] which confirms the successful incorporation of Co into the Mn 3-x Co x O 4 sample. The O 1s XPS spectra are fitted with two characteristic peaks, the O(i) component at around 530.4 eV belongs to O 2- within the lattice of the metal oxide, and the O(ii) component observed at 533 eV is associated with hydroxide ions (OH - ) and/or other chemically adsorbed or dissociated oxygen (O 2- , O 2 2- , or O - ) [49, 51-53] (Figures 4c and S9). The oxidation state ratios of Mn 2+ /Mn 3+ and Co 3+ /Co 2+ , quantified by integrating the deconvoluted XPS spectral areas (Figure 4d and Table S2), reveal distinct trends that the Mn 2+ /Mn 3+ ratio progressively decreases with increasing Co-doping, while the Co 3+ /Co 2+ ratio follows a non-monotonic trend, initially rising before declining and peaking at 60 mol% Co-doping, which is highly similar to the change of specific capacitance. Compared to pure Mn 3 O 4 system (undoped Co 2+ ) with single-step charge storage behavior (the reversible redox transitions of Mn 2+ ↔Mn 3+ , Equations 1), [52] Co 2+ doping induces the Mn 3-x Co x O 4 structural and mechanistic transition, shifting the system to a multi-step redox pathway involving synergistic Mn 2+ /Mn 3+ and Co 2+ /Co 3+ redox couples. (Equations 2-3). [54] Mn 3 O 4 ·2H₂O + OH - ↔ 3MnOOH + H 2 O + e - (1) 2Mn 3- x Co x O 3 + OH - + H 2 O→(3- x ) MnO 2 + x CoOOH+H 2 O + e - (2) Mn 3- x Co x O 4 + OH - + H 2 O→(3- x ) MnOOH + x CoOOH +H 2 O + e - (3) This multistep redox process plays a critical role in determining the material electrochemical behavior through the modulation of the Co 2+ /Co 3+ ratio, wherein the higher oxidation of Co 3+ enhances its charge storage capacity compared to Co 2+ . [55] In Mn 3-x Co x O 4 with 60 mol% Co doping, the optimal synergistic effect between Mn 2+ /Mn 3+ and Co 2+ /Co 3+ redox pairs maximizes electrochemical performance. The strong electron-donating properties of Co 3+ establish a direct correlation between Co valence states and charge storage properties through optimizing the metal-oxygen interaction. CONCLUSION In summary, we have conducted a comprehensive investigation of Co-doping effects in Mn-based oxide through simple hydrothermal synthesis, yielding a series of Mn 3-x Co x O 4 electrode materials. Electrochemical analysis demonstrated a nonlinear dependence of supercapacitor performance on Co-doping concentration, with performance peaking at the optimal 60 mol% Co-doping level, then a gradual decrease was observed at higher concentrations. Notably, the optimal composition in Co-Mn-60 demonstrates exceptional charge storage characteristics, delivering a specific capacitance of 308 F·g -1 at 0.2 A·g -1 and more than 95% capacity retention after 5000 galvanostatic charge-discharge cycles (current density: 1 A·g -1 ), whose performance optimization originates from optimal synergistic effect attributed to the maximized Co 3+ /Co 2+ ratio. Our work offers insightful and effective research ideas for improving the electrochemical performance of supercapacitors by systematically exploring the correlation between the composition-structure-performance of transition metal oxides. 11pt, fleqn, a4paper, ]LegrandOrangeBook Conflicts of interest The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (Nos. 22278349, 52402035), Natural Science Foundation of Hebei Province (No. B2023203026) and Hebei University Basic Research Project of Shijiazhuang City (No. 241791067A). REFERENCES [1]. P. Simon, Y. Gogotsi, B. Dunn. Where Do Batteries End and Supercapacitors Begin? Science , 2014 , 6176 , 1210-1211. [2]. J. Zhang, C.P. Yang, Y. X. Yin, L. J. Wan, Y. G. Guo. Sulfur Encapsulated in Graphitic Carbon Nanocages for High-Rate and Long-Cycle Lithium-Sulfur Batteries . Adv. Mater, 2016 , 28 , 9539-9544. [3]. P. Simon, Y. Gogotsi. 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Keywords cobalt doping electrochemical properties manganese oxide supercapacitors Authors Affiliations Wenwen Kong Yanshan University View all articles by this author Xin Liu Yanshan University View all articles by this author Tianhui Wu [email protected] Yanshan University State Key Laboratory of Metastable Materials Science and Technology View all articles by this author Yang Zhao Yanshan University View all articles by this author Jie Guan Yanshan University View all articles by this author Nianrui Qu Yanshan University View all articles by this author Jianmin Gu Yanshan University State Key Laboratory of Metastable Materials Science and Technology View all articles by this author Desong Wang Yanshan University State Key Laboratory of Metastable Materials Science and Technology View all articles by this author Metrics & Citations Metrics Article Usage 156 views 100 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Wenwen Kong, Xin Liu, Tianhui Wu, et al. 11pt, fleqn, a4paper, ]LegrandOrangeBook Cationic Synergy Engineering by Tuning Co/Mn Ratio for Optimizing Supercapacitors Performance. 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