Nitrogen-Doped Porous Carbon Derived From Bimetallic Zeolitic Imidazolate Frameworks For Electrochemical Li+/Na+ Storage

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Abstract Porous carbon is regarded as one of the most promising anode candidates for Li-ion battery and Na-ion battery. We herein demonstrate a series of nitrogen-doped porous carbon (NPC) by simply carbonizing bimetallic ZnCo-containing zeolitic imidazolate frameworks (ZnCo-ZIFs). The nitrogen content, specific surface area, pore size distribution and microstructure of prepared NPC are balanced by adjusting Zn2+/Co2+ molar ratio of ZnCo-ZIFs and carbonization process parameters. It is found that the optimized ZnCo-ZIF-derived NPC shows promise for electrochemical Li+/Na+ storage, which could be attributed to the hierarchical porous structure, large specific surface area and relatively high N-doping content.
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Nitrogen-Doped Porous Carbon Derived From Bimetallic Zeolitic Imidazolate Frameworks For Electrochemical Li+/Na+ Storage | 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 Research Article Nitrogen-Doped Porous Carbon Derived From Bimetallic Zeolitic Imidazolate Frameworks For Electrochemical Li + /Na + Storage Shuai Dong, Jiewu Cui, Dongbo Yu, Zhongnan Cao, Cuiping Yu, Yong Zhang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-898776/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Jan, 2022 Read the published version in Journal of Solid State Electrochemistry → Version 1 posted You are reading this latest preprint version Abstract Porous carbon is regarded as one of the most promising anode candidates for Li-ion battery and Na-ion battery. We herein demonstrate a series of nitrogen-doped porous carbon (NPC) by simply carbonizing bimetallic ZnCo-containing zeolitic imidazolate frameworks (ZnCo-ZIFs). The nitrogen content, specific surface area, pore size distribution and microstructure of prepared NPC are balanced by adjusting Zn 2+ /Co 2+ molar ratio of ZnCo-ZIFs and carbonization process parameters. It is found that the optimized ZnCo-ZIF-derived NPC shows promise for electrochemical Li + /Na + storage, which could be attributed to the hierarchical porous structure, large specific surface area and relatively high N-doping content. Inorganic Chemistry Ceramics Bimetallic zeolitic imidazolate frameworks Nitrogen-doped porous carbon Li-ion battery Na-ion battery Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Li-ion batteries (LIBs) and Na-ion batteries (SIBs) are considered as the most promising representatives of secondary battery system, which are widely applied in smart grids, portable electronics and electrical vehicles [ 1 , 2 ]. Transition metal oxides, tin, silicon and red phosphorus with high theoretical specific capacity, are common anode materials for LIBs [ 3 – 8 ]. However, during the ion intercalation, these electrodes usually suffer from severe volume expansion and voltage lag, leading to massive irreversible capacity loss and poor stability, and thus hampering their practical application seriously [ 9 ]. Different from LIBs, SIBs have much more sluggish electrochemical kinetics than LIBs, and the larger Na + ion radius results in more rapid capacity fading and structural degradation, which sets higher demands on the electrochemical properties of electrode materials [ 10 – 12 ]. For example, commercial graphite is available for LIBs but no longer suitable for SIBs. Instead, porous carbon has been attracted more attention, which not only owns good electronic conductivity and stability, but also improves ion diffusion and volumetric strain [ 13 – 15 ]. In addition, rational pore distribution, high electrical conductivity and heteroatom doping play positive roles in electrochemical performances [ 16 – 19 ]. Therefore, nanoporous carbon with optimized porous structure and heteroatom doping is expected to show more promise for electrochemical energy storage. As a new type of porous crystal material, metal-organic frameworks (MOFs), assembled by the coordination bonds between organic ligands and inorganic metal ions/clusters, have developed rapidly in recent years [ 20 – 22 ]. Due to the unique structural characteristics, high porosity and specific surface area, MOFs and their derived materials are emerged as outstanding candidates in energy storage, gas separation and nanoreactor, etc. [ 23 – 26 ]. Particularly, ZIFs such as ZIF-8 and ZIF-67 have been extensively studied for energy applications. Benefiting from the N-containing imidazole rings with ZIFs, the derived nanoporous carbon can be self-doped by N heteroatom after a simple carbonization process. At a properly controlled carbonization temperature, NPC derived from Zn-containing ZIF-8 can basically inherit the pore structure of initial precursor, demonstrating large surface area and high N-doping content. Whereas, the amorphous nature of ZIF-8-derived NPC causes low electrical conductivity, greatly suppressing the rate performance [ 24 , 27 ]. By contrast, the reduced metal Co particles within ZIF-67 have strong catalytic effect of graphitization and even facilitate the formation of CNTs [ 28 ]. While the enhancement of electrical conductivity is actually at the cost of surface area and N-doping content, which also hampers the electrochemical storage performances. In view of this, a core-shell hybrid structure is designed to combine advantages of both ZIF-8-derived and ZIF-67-derived NPC [ 24 , 29 ], but the synthesis of such core-shell hybrids requires stepwise procedures. Apart from the construction of core-shell hybrids, bimetallic ZnCo-ZIFs are used as unprecedented templates [ 30 , 31 ]. The agglomeration of Co nanoparticles can be effectively inhibited, as a result, the ZnCo-ZIF-derived NPC inherit both merits of carbon independently from ZIF-8 and ZIF-67, and the features such as surface area, graphitization and N-doping content can be well balanced. More importantly, the synthesis procedure of ZnCo-ZIF is very simple, and the Zn/Co molar ratio can be easily adjusted. To this end, here in this work, we employ bimetallic ZnCo-ZIFs to prepare nanoporous carbon for the anodes of LIBs and SIBs. By optimizing the Zn/Co molar ratio and carbonization temperature, the resulting NPC achieves desirable properties including high surface area and favorable porous structure as well as high N-doping content, which endows with ample active sites, accessible charge transfer and ion diffusion, and thus exhibits excellent Li + /Na + storage performances. Experimental Section 2.1 Material preparation Zinc acetate dehydrate (Zn(CH 3 COO) 2 ·2H 2 O), 2-methylimidazole (2-MeIM), Cobalt acetate tetrahydrate (Co(CH 3 COO) 2 ·4H 2 O), ethanol and other chemicals and raw materials were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China). All chemicals were of analytical reagent grade and used directly without further purification. 2.1.1. Synthesis of ZIF-8 and ZIF-67 polyhedra ZIF-8 polyhedra were prepared by the previously reported procedure with some modifications. 0.53 g of Zn(CH 3 COO) 2 ·2H 2 O was dissolved in 6 ml of deionized water, and 1.97 g of 2-methylimidazole (2-MeIM) was dissolved in 30 ml of deionized water. The two solutions were mixed together and kept at 5°C in a refrigerator for 24 h. The formed white powders were washed with deionized water and ethanol for several times, collected through centrifugation and dried at 80°C in an oven overnight. A similar procedure was applied for the preparation of purple powders of ZIF-67 polyhedra, expect that Zn(CH 3 COO) 2 ·2H 2 O was replaced by Co(CH 3 COO) 2 ·4H 2 O. 2.1.2. Synthesis of ZnCo-ZIF polyhedra The synthesis of ZnCo-ZIF polyhedra with different Zn/Co molar ratio (denoted as xZnyCo-ZIF, where x% and y% were the percentages of Zn and Co, respectively) was similar to that of ZIF-8. Taking the synthesis of 80Zn20Co-ZIF for example. The mixture of 0.42 g of Zn(CH 3 COO) 2 ·2H 2 O and 0.12 g of Co(CH 3 COO) 2 ·4H 2 O was dissolved in 6 ml of deionized water, and 1.97 g of 2-MeIM was dissolved in 30 ml of deionized water. The two solutions were mixed and kept at 5°C in a refrigerator for 24 h. The formed light purple powders were washed with deionized water and ethanol for several times, collected through centrifugation and dried at 80°C. It was worth noting that the total molar amount of Zn(CH 3 COO) 2 ·2H 2 O and Co(CH 3 COO) 2 ·2H 2 O was fixed to be 2.4 mmol. 2.1.3. Preparation of NPCs polyhedra Typically, the prepared ZnCo-ZIF were calcinated at different temperatures (600, 700, 800 or 900°C) under Ar atmosphere for 2 h with a heating rate of 5°C min − 1 . Subsequently, the obtained black powders were added into a diluted HNO 3 solution for 24 h at 80°C to remove Zn and Co species. Finally, the samples were dried at 80°C overnight and denoted as NPC( x Zn- y Co)-T, where T represents the carbonization temperature. 2.2 Materials characterization The phase of the samples was tested by X-ray diffraction (XRD, D/MAX2500 V, Rigaku, Japan) equipped with Cu-Kα radiation (0.15418 nm) at 40 kV, 40 mA. The morphology and structure of the samples was observed by field emission scanning electron microscope (FESEM, SU8020, Hitachi, Japan), field emission transmission electron microscope (FETEM, JEM-2100F, JEOL, Japan), energy dispersive spectroscopy (EDS, Inca, Oxford, UK) and Raman spectra (LabRAM HR Evolution, HORIBA JOBIN YVON). The state of the elements was characterized by X-ray photoelectron spectroscopy (XPS, ESCALAB250, Thermo, US).The thermal gravimetric analysis (TGA) was operated by simultaneous thermal analyzer (STA449F3, Netzsch, Germany). The specific surface area and pore size distribution of the samples were calculated by Brunauer-Emmett-Teller (BET) method with a gas sorption surface area and pore size analyzer (Quadrasorb-EVO). 2.3 Electrochemical measurements The electrochemical behavior of NPCs was studied using CR2032 half coin cells with lithium foil or sodium foil as the counter and reference electrode. The electrode paste was prepared by mixing active materials (NPCs, 80 wt.%), conductive carbon black (10 wt.%) and polyvinylidene fluoride (PVDF, 10 wt.%) in N-methylpyrrolidone. Then the slurry was blade casted onto copper foil uniformly and dried at 60°C for 12 h in a vacuum oven. The mass loading of NPC was about 1 mg cm − 2 . The electrolyte used in the cells was LiPF 6 (1.0 M) in a mixture of ethylene carbonate and diethyl carbonate (1:1 vol %) for LIB, which was replaced by NaClO 4 (1.0 M) in a mixture of ethylene carbonate and propylene carbonate (1:1 vol%) for SIB. The used separator was Whatman GF/D membrane. The cells assembly was operated in an argon-filled glove box with moisture and the oxygen content below 1 ppm. The galvanostatic charge and discharge (GCD) tests and rate capability were measured by a multichannel battery testing system (LANHE, CT-2001A) with a potential range between 0.01 to 3 V, cyclic voltammograms (CV) curves and electrochemical impedance spectra (EIS, frequency ranging from 100 kHz to 0.01 Hz) were tested on a CHI760E electrochemical workstation. Results And Discussion The preparation process of NPCs was illustrated in Fig. 1 . With the increase of Co percentage, the color of prepared ZIFs changed gradually from white (ZIF-8) to deep purple (ZIF-67) (Fig. S1), and the average diameters also increased (Fig. S2 and Fig. 2 a). All the ZIFs were solid particles (Fig. 2 b), and the EDS analysis in Fig. 2 c indicated the uniform distribution of C, N, Zn and Co elements in precursor. In addition, all the XRD patterns of the as-prepared ZIF-8, ZIF-67 and ZnCo-ZIFs were matched well with that of the simulated ZIF-8 (Fig. S3). Calcination temperatures and Zn/Co molar ratio of ZnCo-ZIF play the crucial role in the morphology, structure and properties of the derived NPC. Herein, 40Zn60Co-ZIF is selected as the typical example to investigate the influence of calcination temperatures. According to the TGA and derivative thermogravimetric analysis (Fig. S4), it was obvious to see two major steps of rapid weight loss during the heating treatment. The first step with weight loss approximate 9.6 % could be assigned to the loss of crystal water and the absorbed water, and the second one with 35.6 % weight loss corresponded to the decomposition of the organic species, resulting in the formation of NPCs. Therefore, the calcination temperatures of 40Zn60Co-ZIF should be higher than 600°C. Fig. S5 were SEM images of the resulting NPCs after annealing 40Zn60Co-ZIF at 600, 700, 800 and 900°C. Slight shrinkage was observed in NPCs compared to their precursor, and carbon nanotubes (CNTs) appeared accordingly with calcination temperature, resulting from the catalytic function of Co [ 28 – 31 ]. The influence of Zn/Co molar ratio on the derived NPC was also investigated. As displayed in Fig. S5a, Fig. S6 and Fig. 3 a, all the polyhedra had rough surface, while there was less or even no CNTs grown on the surface of NPCs such as NPC(100Zn)-600°C and NPC(80Zn-20Co)-600°C. The amount of CNTs increased with the increasing Co content, because the more Co content caused the agglomeration of Co clusters which boosted the catalytic effect on graphitization of carbon [ 32 ]. The TEM and HRTEM images in Fig. 3 b-d further confirmed the existence of CNTs, and small amount of Co nanoparticles enwrapped by CNTs were retained after HNO 3 etching process. Moreover, C and N elements were uniformly distributed in NPC(20Zn-80Co)-600°C (Fig. 3 e), indicating the self-doping of heteroatom N. Figure 4 a shows the XRD patterns of NPC( x Zn- y Co)-600°C, all the XRD patterns of NPC exhibit two peaks around 26° and 44°, corresponding to (002) and (101) planes of carbon, respectively. Particularly, another peak located at ~ 22° emerged for NPC(100Zn)-600°C, suggesting the formation of amorphous carbon [ 33 ]. It was worth to note that the peak around 26° became stronger with the increasing cobalt content, resulting from the graphitization of amorphous carbon by catalysis of Co nanoparticles [ 34 ]. In the Raman spectra (Fig. 4 b), all the samples displayed two distinct peaks at 1353 and 1590 cm -1 , which were the disordered carbon (D band) and the ordered graphitized carbon (G band), respectively. The intensity ratio of D band and G band (I D /I G ) reflects the crystal defects and graphitization degree of carbon materials. The decrease of I D /I G values from 1.08 to 0.98 demonstrated the reduction of lattice defects and the improvement of the graphitization degree [ 35 ]. XPS was conducted to further analyze the chemical composition of all the NPC materials. Fig. S7a shows the survey spectrum of NPC(40Zn-60Co)-T (T = 600°C, 700°C, 800°C and 900°C,) the three main peaks correspond to the C 1s, N 1s and O 1s, revealing the effective removal of Zn and Co during the carbonization and acid washing processes. Fig S7b-e are the high-resolution C 1s XPS spectra, the peak centered at 284.8, 285.8 and 288.5 eV correspond to C-C bonds of sp 2 carbon, C = O and C-N functional groups, respectively [ 19 ]. The small peak at 291.7 eV can be ascribed to π-π electronic transitions [ 35 ]. Fig. S8a-d show the N 1s XPS spectrum of NPC(40Zn-60Co)-T, the N 1s spectrum can be fitted into three peaks, including pyridinic N (398.6 ± 0.1 eV), pyrrolic N (399.9 ± 0.1 eV) and graphitic N (400.7 ± 0.4 eV) [ 36 , 37 ]. The detailed N content values of ZIF(40Zn-60Co)-T-derived NPCs are summarized in Fig. S8e and Table S1. Obviously, the increase of annealing temperature leads to the decrease of nitrogen content in carbon materials because of the breakage of C-N bond at high temperature, thus NPC(40Zn-60Co)-600°C has 10.74% of N-doping content, which is higher than 9.77% for NPC(40Zn-60Co)-700°C, 5.90% for NPC(40Zn-60Co)-800°C and 4.90% for NPC(40Zn-60Co)-900°C. In addition, the proportion of graphitic N in the total nitrogen content also increases from 14.3–47.5% with the increase of calcination temperature, stemming from the transformation of pyrrolic N and pyridinic N into graphitic N [ 38 ]. The overview XPS spectra of NPC( x Zn- y Co)-600°C with different Zn/Co molar ratio are shown in Fig. S9a. Similar to NPC(40Zn-60Co)-T, four peaks were fitted in the high-resolution C 1s XPS spectrum of NPC( x Zn- y Co)-600°C (Fig. S9b-f) and three peaks were also in high-resolution N 1s spectra (Fig. 4 c, Fig. S10). The total N-doping content gradually raised with the increasing Zn/Co molar ratio (Fig. 4 d and Table S2), because the existence of cobalt also result in the fracture of C-N bond, which shows similar effect as high temperature. Note that pyrrolic N and pyridinic N can not only absorb Li + /Na + ions to afford additional capacity, but also promote the ion diffusion for rate performance; in addition, graphitic N can enhance the electronic conductivity [ 17 ]. The specific surface area and porous structure also play the important role on the Li + /Na + storage performance, which are evaluated by N 2 adsorption-desorption analysis. NPC(40Zn-60Co)-600°C, NPC(40Zn-60Co)-700°C, NPC(40Zn-60Co)- 800°C and NPC(40Zn-60Co)-900°C have 313.0, 259.4, 363.1 and 411.0 m 2 g -1 of specific surface area, respectively (Fig. S11). In addition, the specific surface areas of NPC(100Zn)-600°C, NPC(80Zn-20Co)-600°C, NPC(60Zn-40Co)-600°C, NPC(20Zn-80Co)-600°C and NPC(100Co)-600°C are determined as 16.9, 21.1, 193.5, 313.0 and 352.8 m 2 g -1 , respectively (Fig. S12). We can see Zn-rich NPC(100Zn)-600°C and NPC(80Zn-20Co)-600°C show very low specific surface area, which is caused by their poor catalytic by Co to the formation of graphite carbon[ 39 ]. Very interesting, all samples demonstrate a kind of hierarchically porous structure, as micropores can supply numerous electroactive sites for high capacity, and mesopores can boost the ion transfer for superior rate performance [ 40 ]. The electrochemical performance of NPC( x Zn- y Co)-T for Li + storage are investigated by CV and GCD techniques in the potential range of 0.01-3.0 V vs . Li + /Li. Fig. S13a shows the initial three CV curves of NPC(20Zn-80Co)-600°C at a scan rate of 0.1 mV s − 1 , an obvious peak appears around 0.6 V at the first cycle, which is due to the formation of solid-electrolyte-interphase (SEI) film on the surface of the electrode, and the peak near 0 V results from insertion of Li + in the porous carbon [ 41 ]. The second cycle and the third cycle almost overlap each other, indicating the excellent electrochemical reversibility of NPC(20Zn-80Co)-600°C. Figure 5 a shows the CV curves of NPC(20Zn-80Co)-600°C at different scan rates. The electrochemical reaction kinetics can be evaluated according to the following equations [ 42 ]: i = av b (1) log i = b log v + log a (2) where i and v are the response current and scan rate, respectively, a and b are adjustable constants in which b value could be determined from the slope of log i versus log v curve from Eq. ( 2 ). If b = 0.5, the reaction is subjected to diffusion-control behavior, while b = 1, the kinetics is controlled by capacitive behavior [ 43 ]. Herein, the b values at different potentials range from 0.5 to 1 (Fig. 5 b), suggesting the co-existence of diffusion and capacitive controlled processes. In addition, the total capacity could be divided into a diffusion controlled part ( k 1 v 1/2 ) and a capacitive controlled one ( k 2 v ) at a fixed potential (V) according to the following equations [ 44 ]: i(V) = k 1 v 1/2 +k 2 v (3) i(V) / v 1/2 = k 1 + k 2 v 1/2 (3) It can be seen that the capacitive control behavior gradually dominates the total capacity, and the capacitive control contribution increases from 52.3 % at 0.1 mV s − 1 to 83.2 % at 2 mV s − 1 (Fig. 5 c), revealing the superior rate performance of NPC(20Zn-80Co)-600°C. Figure 5 d shows the typical GCD curves of NPC(20Zn-80Co)-600°C at the current density of 0.1 A g − 1 for the first three cycles. The initial charging and discharging specific capacity of NPC(20Zn-80Co)-600°C are 804.2 and 1251.9 mA h g − 1 with the coulombic efficiency (CE) of 64 %, which is originated from the irreversible processes such as decomposition of electrolyte and the formation of SEI film [ 45 ]. The influence of calcination temperatures and the initial Zn 2+ /Co 2+ molar ratios on the rate capability are investigated. Fig. S13b shows the rate capability of NPC(40Zn-60Co)-T from 0.1 A g − 1 to 5 A g − 1 , it can be observed that NPC(40Zn-60Co)-600°C delivers 786.0, 736.9, 634.9, 521.8, 401.1 and 254.1 mA h g − 1 at current density of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g − 1 , respectively. When the current density returns to 0.1 A g − 1 , a capacity as high as 783.6 mA h g − 1 still can be achieved. NPC(40Zn-60Co)-600°C has superior rate capability compared with other counterparts, thus proving the optimized calcination temperature of 600°C. Secondly, the rate capability of NPC( x Zn- y Co)-600°C derived from precursor with different Zn 2+ /Co 2+ molar ratio are displayed in Fig. 5 e. NPC(20Zn-80Co)-600°C exhibits reversible capacity of 876.5, 768.9, 664.7, 570.7, 480.9 and 352.6 mA h g − 1 at current density of 0.1, 0.2, 0.5, 1, 2 and 5 A g − 1 , respectively, which are higher than other NPC( x Zn- y Co)-600°C. More importantly, when the current density is back to 0.1 A g − 1 , NPC(20Zn-80Co)-600°C shows a capacity of 857.9 mA h g − 1 , which is closed to the initial specific capacity. The excellent Li + storage performance of NPC(20Zn-80Co)-600°C results from the aforementioned high nitrogen content, big specific surface area, suitable porous structure and pore size. Figure S13c and Fig. 5 f show the cycling performance of NPC(20Zn-80Co)-600°C at low and high current densities, respectively. NPC(20Zn-80Co)-600°C could retain 98.3 % after 100 cycles at 0.1 A g − 1 and 99.8 % after 500 cycles at 1 A g − 1 . The coulombic efficiencies reach almost 100% after the first cycle, indicating the excellent long-term stability. The charge transfer kinetics of the NPC( x Zn- y Co)-600°C are further investigated by EIS, it can be noticed from Fig. S13d that the Nyquist plots for all the samples are similar and each curve consists of a semicircle in the high frequency region and an approximate oblique line in the low frequency region. The semicircle of the high frequency region corresponds to the charge transfer resistance (R ct ) generated by the contact between the active material and electrolyte solution, and the contact between the interfacial active material and the copper foil collector fluid. The slant area in the low frequency region represents the Warburg impedance (Z w ), which is related to the diffusion of Li + into the electrode [ 46 ]. NPC(20Zn-80Co)-600°C exhibits the minimum semicircle compared with that of other NPC, suggesting the minimum charge transfer resistance and Warburg resistance. It could be concluded that the unique hierarchical porous structure with a high specific surface area not only provides a rapid transport channel, but also reduces the transport path of Li + . In addition, the as-prepared NPC(20Zn-80Co)-600°C has better Li + storage properties compared with other reported porous carbon-based materials (Table S3). Meantime, NPC-(20Zn-80Co)-600°C are also suitable for electrochemical Na + storage. Fig. S14a shows the initial three CV curves at scan rate of 0.1 mV s − 1 , the first irreversible reduction peak around 0.6 V in the CV curve is mainly caused by the formation of SEI film [ 47 ] and the peak located around 0 V suggests the sodium ion insertion into NPC(20Zn-80Co)-600°C [ 48 ]. In addition, the CV curves almost overlapped with each other in the second and third cycles, indicating that NPC(20Zn-80Co)-600°C electrode materials have good cycling performance in the process of Na + intercalation/de-intercalation. In addition, a rectangular area can be observed in potential range of 1.5-3 V, suggesting a capacitive behavior [ 49 ]. Figure 6 a illustrates the CV curves of NPC(20Zn-80Co)-600°C at different scan rates ranging from 0.1 to 2.0 mV s − 1 with the similar shape, revealing its high reversibility and good repeatability in the electrochemical reactions. Similar to Li + storage, the energy storage mechanism in Na + storage is also controlled by both diffusion behavior and capacitance behavior (Fig. 6 b). As demonstrated in Fig. 6 c, through quantitative analysis of capacitance control behavior and diffusion control behavior, the behavior of capacitive control accounts for a large part of the total capacity at each scan rate, ranging from 53.9 % (at 0.1 mV s − 1 ) to 83.2 % (at 2.0 mV s − 1 ), which indicates high proportion of pseudocapacitance of the total capacitance contribution. Figure 6 d illustrates the first three GCD curves of NPC(20Zn-80Co)-600°C at a current density of 0.02 A g − 1 , the initial discharging and charging specific capacity are 872.0 and 377.2 mA h g-1, respectively, and the initial coulombic efficiency is 43.3 % (Fig. S14a). NPC(20Zn-80Co)-600°C also presents excellent rate capability and cycling stability. NPC(20Zn-80Co)-600°C delivers reversible capacity of 416.1, 291.6, 245.0, 206.6, 172.7, 144.0, 125.2 and 113.0 mA h g − 1 at current densities of 0.02, 0.05, 0.1, 0.2, 0.5, 1, 1.5 and 2 A g − 1 , respectively, which could still retain to 276 mA h g − 1 when the current density immediately returns to 0.02 A g − 1 . after 450 cycles at 0.05 A g − 1 , it exhibits a capacity of 218.0 mA h g − 1 (Fig. S14b), and a reversible specific capacity of 117.8 mA h g − 1 could be retained after 1000 cycles at high current density of 1 A g − 1 (Fig. 6 f). In addition, the coulombic efficiency is almost closed to 100% after the first cycle, demonstrating that NPC(20Zn-80Co)-600°C has remarkable long-term cycling stability. The Na + storage performance of NPC(20Zn-80Co)-600°C is also comparable with other reported porous carbon-based materials (Table S4). Conclusions In summary, ZnCo-ZIF-derived NPC are prepared by a simple carbonization treatment. The Zn/Co molar ratio within the initial ZnCo-ZIF and the carbonization temeperature are optimized to balance the morphology, nitrogen content, specific surface area and porous structure of the derived NPC. It is found that NPC(20Zn-80Co)-600°C shows excellent electrochemical properties for Li + /Na + storage. The as-prepared NPC are expected to be promising alternatives for the application in energy storage and other related fields. Declarations Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements We acknowledge the funding support from the National Natural Science Foundation of China (U1810204), the Natural Science Foundation of Anhui Province (2108085MB45) and the Fundamental Research Funds for the Central Universities (JZ2020HGTB0059, PA2021KCPY0044 and PA2020GDSK0087). 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Carbon 55:328–334 Cao Y, Xiao L, Sushko ML, Wang W, Schwenzer B, Xiao J, Nie Z, Saraf LV, Yang Z, Liu J (2012) Sodium ion insertion in hollow carbon nanowires for battery applications. Nano Lett 12:3783–3787 Zhong J, Yi F, Gao A, Shu D, Huang Y, Li Z, Zhu W, He C, Meng T, Zhao S (2017) Preparation of 3D reduced graphene oxide/MnO 2 nanocomposites through a vacuum-impregnation method and their electrochemical capacitive behavior. ChemElectroChem 4:1088–1094 Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Published Journal Publication published 20 Jan, 2022 Read the published version in Journal of Solid State Electrochemistry → 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. 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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-898776","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":52022122,"identity":"6e70353b-0d0b-43a4-89c5-f5145c174a67","order_by":0,"name":"Shuai Dong","email":"","orcid":"","institution":"Hefei University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Shuai","middleName":"","lastName":"Dong","suffix":""},{"id":52022123,"identity":"48067759-cccc-44e7-932e-50c4e67155f0","order_by":1,"name":"Jiewu 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1","display":"","copyAsset":false,"role":"figure","size":151866,"visible":true,"origin":"","legend":"Schematic illustration for the fabrication of NPCs.","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/5458026d45273f493797af10.png"},{"id":13891281,"identity":"7090bbd7-9a9e-4bf9-989d-8c0a6e042c1e","added_by":"auto","created_at":"2021-09-22 22:28:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":392326,"visible":true,"origin":"","legend":"SEM (a), TEM (b) and EDS mapping (c) images of 20Zn80Co-ZIF.","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/08318862a2ec48e48dd86274.png"},{"id":13890523,"identity":"0c896d8e-3cfd-404e-9b26-6dbe429555fb","added_by":"auto","created_at":"2021-09-22 22:22:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1146549,"visible":true,"origin":"","legend":"SEM (a), TEM (b, c), HRTEM (d) and EDS mapping (e) images of NPC(20Zn-80Co)-600°C.","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/1a494af303dced134f960e13.png"},{"id":13890951,"identity":"fa6ea757-4e53-4026-928d-41b992b852fb","added_by":"auto","created_at":"2021-09-22 22:25:58","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":237830,"visible":true,"origin":"","legend":"XRD patterns (a) and Raman spectra (b) of NPC(xZn-yCo)-600°C, N 1s spectrum of NPC(20Zn-80Co)-600°C (c) and the overall N-doping contents of NPC(xZn-yCo)-600°C (d). ","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/c9d4a561fd65b4add8ec3e94.png"},{"id":13890952,"identity":"1b2329a6-9530-40b4-9f81-2487105e1e72","added_by":"auto","created_at":"2021-09-22 22:25:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":217517,"visible":true,"origin":"","legend":"Li+ storage performance: (a) CV curves of NPC(20Zn-80Co)-600°C at different scan rates (from 0.1 to 2 mV s-1), (b) Relationship between current and scan rate of NPC(20Zn-80Co)-600°C, (c) Contribution ratio of capacitive and diffusion controlled at different scan rate, (d) First three GCD curves of NPC(20Zn-80Co)-600°C at current density of 100 mA g-1, (e) Rate capability of NPC(xZn-yCo)-600°C, (f) Cycling stability of NPC(20Zn-80Co)-600°C at 1 A g-1 for 500 cycles. ","description":"","filename":"fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/d05ffe14a7f99c2b225745c9.png"},{"id":13890521,"identity":"7cd38027-5c7e-4c8f-ad48-961a57cde3b7","added_by":"auto","created_at":"2021-09-22 22:22:58","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":188662,"visible":true,"origin":"","legend":"Na+ storage performance of NPC(20Zn-80Co)-600°C: (a) CV curves at different scan rates ranging from 0.1 to 2 mV s-1, (b) Relationship between current and scan rate, (c) Contribution ratio of capacitive and diffusion controlled at different scan rate, (d) First three GCD curves at current density of 0.02 A g-1, (e) Rate capability and (f) Cycling stability at 1 A g-1 for 1000 cycles.","description":"","filename":"fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/e44a50df87a3f10bfdd669b1.png"},{"id":18151099,"identity":"bb93b315-a367-4b0f-a4f6-cc0e6da03148","added_by":"auto","created_at":"2022-02-12 01:04:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2443405,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/694f850c-2ac5-45bc-b634-34e90a05b2f4.pdf"},{"id":13890526,"identity":"d4de78ef-7f53-4d64-b00e-0d805b5f0e13","added_by":"auto","created_at":"2021-09-22 22:22:58","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":7621115,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-898776/v1/fc1b16f632e4732607c0a2c6.docx"}],"financialInterests":"","formattedTitle":"\u003cp\u003eNitrogen-Doped Porous Carbon Derived From Bimetallic Zeolitic Imidazolate Frameworks For Electrochemical Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e Storage\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLi-ion batteries (LIBs) and Na-ion batteries (SIBs) are considered as the most promising representatives of secondary battery system, which are widely applied in smart grids, portable electronics and electrical vehicles [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Transition metal oxides, tin, silicon and red phosphorus with high theoretical specific capacity, are common anode materials for LIBs [\u003cspan additionalcitationids=\"CR4 CR5 CR6 CR7\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, during the ion intercalation, these electrodes usually suffer from severe volume expansion and voltage lag, leading to massive irreversible capacity loss and poor stability, and thus hampering their practical application seriously [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Different from LIBs, SIBs have much more sluggish electrochemical kinetics than LIBs, and the larger Na\u003csup\u003e+\u003c/sup\u003e ion radius results in more rapid capacity fading and structural degradation, which sets higher demands on the electrochemical properties of electrode materials [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. For example, commercial graphite is available for LIBs but no longer suitable for SIBs. Instead, porous carbon has been attracted more attention, which not only owns good electronic conductivity and stability, but also improves ion diffusion and volumetric strain [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In addition, rational pore distribution, high electrical conductivity and heteroatom doping play positive roles in electrochemical performances [\u003cspan additionalcitationids=\"CR17 CR18\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Therefore, nanoporous carbon with optimized porous structure and heteroatom doping is expected to show more promise for electrochemical energy storage.\u003c/p\u003e \u003cp\u003eAs a new type of porous crystal material, metal-organic frameworks (MOFs), assembled by the coordination bonds between organic ligands and inorganic metal ions/clusters, have developed rapidly in recent years [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Due to the unique structural characteristics, high porosity and specific surface area, MOFs and their derived materials are emerged as outstanding candidates in energy storage, gas separation and nanoreactor, etc. [\u003cspan additionalcitationids=\"CR24 CR25\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Particularly, ZIFs such as ZIF-8 and ZIF-67 have been extensively studied for energy applications. Benefiting from the N-containing imidazole rings with ZIFs, the derived nanoporous carbon can be self-doped by N heteroatom after a simple carbonization process. At a properly controlled carbonization temperature, NPC derived from Zn-containing ZIF-8 can basically inherit the pore structure of initial precursor, demonstrating large surface area and high N-doping content. Whereas, the amorphous nature of ZIF-8-derived NPC causes low electrical conductivity, greatly suppressing the rate performance [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. By contrast, the reduced metal Co particles within ZIF-67 have strong catalytic effect of graphitization and even facilitate the formation of CNTs [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. While the enhancement of electrical conductivity is actually at the cost of surface area and N-doping content, which also hampers the electrochemical storage performances. In view of this, a core-shell hybrid structure is designed to combine advantages of both ZIF-8-derived and ZIF-67-derived NPC [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], but the synthesis of such core-shell hybrids requires stepwise procedures. Apart from the construction of core-shell hybrids, bimetallic ZnCo-ZIFs are used as unprecedented templates [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The agglomeration of Co nanoparticles can be effectively inhibited, as a result, the ZnCo-ZIF-derived NPC inherit both merits of carbon independently from ZIF-8 and ZIF-67, and the features such as surface area, graphitization and N-doping content can be well balanced. More importantly, the synthesis procedure of ZnCo-ZIF is very simple, and the Zn/Co molar ratio can be easily adjusted.\u003c/p\u003e \u003cp\u003eTo this end, here in this work, we employ bimetallic ZnCo-ZIFs to prepare nanoporous carbon for the anodes of LIBs and SIBs. By optimizing the Zn/Co molar ratio and carbonization temperature, the resulting NPC achieves desirable properties including high surface area and favorable porous structure as well as high N-doping content, which endows with ample active sites, accessible charge transfer and ion diffusion, and thus exhibits excellent Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e storage performances.\u003c/p\u003e"},{"header":"Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Material preparation\u003c/h2\u003e \u003cp\u003eZinc acetate dehydrate (Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO), 2-methylimidazole (2-MeIM), Cobalt acetate tetrahydrate (Co(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO), ethanol and other chemicals and raw materials were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China). All chemicals were of analytical reagent grade and used directly without further purification.\u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1. Synthesis of ZIF-8 and ZIF-67 polyhedra\u003c/h2\u003e \u003cp\u003eZIF-8 polyhedra were prepared by the previously reported procedure with some modifications. 0.53 g of Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO was dissolved in 6 ml of deionized water, and 1.97 g of 2-methylimidazole (2-MeIM) was dissolved in 30 ml of deionized water. The two solutions were mixed together and kept at 5\u0026deg;C in a refrigerator for 24 h. The formed white powders were washed with deionized water and ethanol for several times, collected through centrifugation and dried at 80\u0026deg;C in an oven overnight. A similar procedure was applied for the preparation of purple powders of ZIF-67 polyhedra, expect that Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO was replaced by Co(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.1.2. Synthesis of ZnCo-ZIF polyhedra\u003c/h2\u003e \u003cp\u003eThe synthesis of ZnCo-ZIF polyhedra with different Zn/Co molar ratio (denoted as xZnyCo-ZIF, where x% and y% were the percentages of Zn and Co, respectively) was similar to that of ZIF-8. Taking the synthesis of 80Zn20Co-ZIF for example. The mixture of 0.42 g of Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO and 0.12 g of Co(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO was dissolved in 6 ml of deionized water, and 1.97 g of 2-MeIM was dissolved in 30 ml of deionized water. The two solutions were mixed and kept at 5\u0026deg;C in a refrigerator for 24 h. The formed light purple powders were washed with deionized water and ethanol for several times, collected through centrifugation and dried at 80\u0026deg;C. It was worth noting that the total molar amount of Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO and Co(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO was fixed to be 2.4 mmol.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.1.3. Preparation of NPCs polyhedra\u003c/h2\u003e \u003cp\u003eTypically, the prepared ZnCo-ZIF were calcinated at different temperatures (600, 700, 800 or 900\u0026deg;C) under Ar atmosphere for 2 h with a heating rate of 5\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Subsequently, the obtained black powders were added into a diluted HNO\u003csub\u003e3\u003c/sub\u003e solution for 24 h at 80\u0026deg;C to remove Zn and Co species. Finally, the samples were dried at 80\u0026deg;C overnight and denoted as NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-T, where T represents the carbonization temperature.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Materials characterization\u003c/h2\u003e \u003cp\u003eThe phase of the samples was tested by X-ray diffraction (XRD, D/MAX2500 V, Rigaku, Japan) equipped with Cu-Kα radiation (0.15418 nm) at 40 kV, 40 mA. The morphology and structure of the samples was observed by field emission scanning electron microscope (FESEM, SU8020, Hitachi, Japan), field emission transmission electron microscope (FETEM, JEM-2100F, JEOL, Japan), energy dispersive spectroscopy (EDS, Inca, Oxford, UK) and Raman spectra (LabRAM HR Evolution, HORIBA JOBIN YVON). The state of the elements was characterized by X-ray photoelectron spectroscopy (XPS, ESCALAB250, Thermo, US).The thermal gravimetric analysis (TGA) was operated by simultaneous thermal analyzer (STA449F3, Netzsch, Germany). The specific surface area and pore size distribution of the samples were calculated by Brunauer-Emmett-Teller (BET) method with a gas sorption surface area and pore size analyzer (Quadrasorb-EVO).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Electrochemical measurements\u003c/h2\u003e \u003cp\u003eThe electrochemical behavior of NPCs was studied using CR2032 half coin cells with lithium foil or sodium foil as the counter and reference electrode. The electrode paste was prepared by mixing active materials (NPCs, 80 wt.%), conductive carbon black (10 wt.%) and polyvinylidene fluoride (PVDF, 10 wt.%) in N-methylpyrrolidone. Then the slurry was blade casted onto copper foil uniformly and dried at 60\u0026deg;C for 12 h in a vacuum oven. The mass loading of NPC was about 1 mg cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The electrolyte used in the cells was LiPF\u003csub\u003e6\u003c/sub\u003e (1.0 M) in a mixture of ethylene carbonate and diethyl carbonate (1:1 vol %) for LIB, which was replaced by NaClO\u003csub\u003e4\u003c/sub\u003e (1.0 M) in a mixture of ethylene carbonate and propylene carbonate (1:1 vol%) for SIB. The used separator was Whatman GF/D membrane. The cells assembly was operated in an argon-filled glove box with moisture and the oxygen content below 1 ppm. The galvanostatic charge and discharge (GCD) tests and rate capability were measured by a multichannel battery testing system (LANHE, CT-2001A) with a potential range between 0.01 to 3 V, cyclic voltammograms (CV) curves and electrochemical impedance spectra (EIS, frequency ranging from 100 kHz to 0.01 Hz) were tested on a CHI760E electrochemical workstation.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003eThe preparation process of NPCs was illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. With the increase of Co percentage, the color of prepared ZIFs changed gradually from white (ZIF-8) to deep purple (ZIF-67) (Fig. S1), and the average diameters also increased (Fig. S2 and Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea). All the ZIFs were solid particles (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb), and the EDS analysis in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec indicated the uniform distribution of C, N, Zn and Co elements in precursor. In addition, all the XRD patterns of the as-prepared ZIF-8, ZIF-67 and ZnCo-ZIFs were matched well with that of the simulated ZIF-8 (Fig. S3).\u003c/p\u003e\n\u003cp\u003eCalcination temperatures and Zn/Co molar ratio of ZnCo-ZIF play the crucial role in the morphology, structure and properties of the derived NPC. Herein, 40Zn60Co-ZIF is selected as the typical example to investigate the influence of calcination temperatures. According to the TGA and derivative thermogravimetric analysis (Fig. S4), it was obvious to see two major steps of rapid weight loss during the heating treatment. The first step with weight loss approximate 9.6 % could be assigned to the loss of crystal water and the absorbed water, and the second one with 35.6 % weight loss corresponded to the decomposition of the organic species, resulting in the formation of NPCs. Therefore, the calcination temperatures of 40Zn60Co-ZIF should be higher than 600\u0026deg;C. Fig. S5 were SEM images of the resulting NPCs after annealing 40Zn60Co-ZIF at 600, 700, 800 and 900\u0026deg;C. Slight shrinkage was observed in NPCs compared to their precursor, and carbon nanotubes (CNTs) appeared accordingly with calcination temperature, resulting from the catalytic function of Co [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe influence of Zn/Co molar ratio on the derived NPC was also investigated. As displayed in Fig. S5a, Fig. S6 and Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea, all the polyhedra had rough surface, while there was less or even no CNTs grown on the surface of NPCs such as NPC(100Zn)-600\u0026deg;C and NPC(80Zn-20Co)-600\u0026deg;C. The amount of CNTs increased with the increasing Co content, because the more Co content caused the agglomeration of Co clusters which boosted the catalytic effect on graphitization of carbon [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]. The TEM and HRTEM images in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb-d further confirmed the existence of CNTs, and small amount of Co nanoparticles enwrapped by CNTs were retained after HNO\u003csub\u003e3\u003c/sub\u003e etching process. Moreover, C and N elements were uniformly distributed in NPC(20Zn-80Co)-600\u0026deg;C (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ee), indicating the self-doping of heteroatom N.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea shows the XRD patterns of NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C, all the XRD patterns of NPC exhibit two peaks around 26\u0026deg; and 44\u0026deg;, corresponding to (002) and (101) planes of carbon, respectively. Particularly, another peak located at ~\u0026thinsp;22\u0026deg; emerged for NPC(100Zn)-600\u0026deg;C, suggesting the formation of amorphous carbon [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. It was worth to note that the peak around 26\u0026deg; became stronger with the increasing cobalt content, resulting from the graphitization of amorphous carbon by catalysis of Co nanoparticles [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]. In the Raman spectra (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb), all the samples displayed two distinct peaks at 1353 and 1590 cm\u003csup\u003e-1\u003c/sup\u003e, which were the disordered carbon (D band) and the ordered graphitized carbon (G band), respectively. The intensity ratio of D band and G band (I\u003csub\u003eD\u003c/sub\u003e/I\u003csub\u003eG\u003c/sub\u003e) reflects the crystal defects and graphitization degree of carbon materials. The decrease of I\u003csub\u003eD\u003c/sub\u003e/I\u003csub\u003eG\u003c/sub\u003e values from 1.08 to 0.98 demonstrated the reduction of lattice defects and the improvement of the graphitization degree [\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eXPS was conducted to further analyze the chemical composition of all the NPC materials. Fig. S7a shows the survey spectrum of NPC(40Zn-60Co)-T (T\u0026thinsp;=\u0026thinsp;600\u0026deg;C, 700\u0026deg;C, 800\u0026deg;C and 900\u0026deg;C,) the three main peaks correspond to the C 1s, N 1s and O 1s, revealing the effective removal of Zn and Co during the carbonization and acid washing processes. Fig S7b-e are the high-resolution C 1s XPS spectra, the peak centered at 284.8, 285.8 and 288.5 eV correspond to C-C bonds of sp\u003csup\u003e2\u003c/sup\u003e carbon, C\u0026thinsp;=\u0026thinsp;O and C-N functional groups, respectively [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]. The small peak at 291.7 eV can be ascribed to \u0026pi;-\u0026pi; electronic transitions [\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e]. Fig. S8a-d show the N 1s XPS spectrum of NPC(40Zn-60Co)-T, the N 1s spectrum can be fitted into three peaks, including pyridinic N (398.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 eV), pyrrolic N (399.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 eV) and graphitic N (400.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 eV) [\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e]. The detailed N content values of ZIF(40Zn-60Co)-T-derived NPCs are summarized in Fig. S8e and Table S1. Obviously, the increase of annealing temperature leads to the decrease of nitrogen content in carbon materials because of the breakage of C-N bond at high temperature, thus NPC(40Zn-60Co)-600\u0026deg;C has 10.74% of N-doping content, which is higher than 9.77% for NPC(40Zn-60Co)-700\u0026deg;C, 5.90% for NPC(40Zn-60Co)-800\u0026deg;C and 4.90% for NPC(40Zn-60Co)-900\u0026deg;C. In addition, the proportion of graphitic N in the total nitrogen content also increases from 14.3\u0026ndash;47.5% with the increase of calcination temperature, stemming from the transformation of pyrrolic N and pyridinic N into graphitic N [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]. The overview XPS spectra of NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C with different Zn/Co molar ratio are shown in Fig. S9a. Similar to NPC(40Zn-60Co)-T, four peaks were fitted in the high-resolution C 1s XPS spectrum of NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C (Fig. S9b-f) and three peaks were also in high-resolution N 1s spectra (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec, Fig. S10). The total N-doping content gradually raised with the increasing Zn/Co molar ratio (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ed and Table S2), because the existence of cobalt also result in the fracture of C-N bond, which shows similar effect as high temperature. Note that pyrrolic N and pyridinic N can not only absorb Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e ions to afford additional capacity, but also promote the ion diffusion for rate performance; in addition, graphitic N can enhance the electronic conductivity [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe specific surface area and porous structure also play the important role on the Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e storage performance, which are evaluated by N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption analysis. NPC(40Zn-60Co)-600\u0026deg;C, NPC(40Zn-60Co)-700\u0026deg;C, NPC(40Zn-60Co)- 800\u0026deg;C and NPC(40Zn-60Co)-900\u0026deg;C have 313.0, 259.4, 363.1 and 411.0 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e of specific surface area, respectively (Fig. S11). In addition, the specific surface areas of NPC(100Zn)-600\u0026deg;C, NPC(80Zn-20Co)-600\u0026deg;C, NPC(60Zn-40Co)-600\u0026deg;C, NPC(20Zn-80Co)-600\u0026deg;C and NPC(100Co)-600\u0026deg;C are determined as 16.9, 21.1, 193.5, 313.0 and 352.8 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e, respectively (Fig. S12). We can see Zn-rich NPC(100Zn)-600\u0026deg;C and NPC(80Zn-20Co)-600\u0026deg;C show very low specific surface area, which is caused by their poor catalytic by Co to the formation of graphite carbon[\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. Very interesting, all samples demonstrate a kind of hierarchically porous structure, as micropores can supply numerous electroactive sites for high capacity, and mesopores can boost the ion transfer for superior rate performance [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe electrochemical performance of NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-T for Li\u003csup\u003e+\u003c/sup\u003e storage are investigated by CV and GCD techniques in the potential range of 0.01-3.0 V \u003cem\u003evs\u003c/em\u003e. Li\u003csup\u003e+\u003c/sup\u003e/Li. Fig. S13a shows the initial three CV curves of NPC(20Zn-80Co)-600\u0026deg;C at a scan rate of 0.1 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, an obvious peak appears around 0.6 V at the first cycle, which is due to the formation of solid-electrolyte-interphase (SEI) film on the surface of the electrode, and the peak near 0 V results from insertion of Li\u003csup\u003e+\u003c/sup\u003e in the porous carbon [\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]. The second cycle and the third cycle almost overlap each other, indicating the excellent electrochemical reversibility of NPC(20Zn-80Co)-600\u0026deg;C. Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the CV curves of NPC(20Zn-80Co)-600\u0026deg;C at different scan rates. The electrochemical reaction kinetics can be evaluated according to the following equations [\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]:\u003c/p\u003e\n\u003cdiv class=\"Equation\" id=\"Equ1\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003ei = av\u003csup\u003eb\u003c/sup\u003e\u0026nbsp; \u0026nbsp; (1)\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Equation\" id=\"Equ2\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003elog i = b log v + log a \u0026nbsp;(2)\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003ewhere \u003cem\u003ei\u003c/em\u003e and \u003cem\u003ev\u003c/em\u003e are the response current and scan rate, respectively, \u003cem\u003ea\u003c/em\u003e and \u003cem\u003eb\u003c/em\u003e are adjustable constants in which \u003cem\u003eb\u003c/em\u003e value could be determined from the slope of log \u003cem\u003ei\u003c/em\u003e versus log \u003cem\u003ev\u003c/em\u003e curve from Eq. (\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). If \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.5, the reaction is subjected to diffusion-control behavior, while \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1, the kinetics is controlled by capacitive behavior [\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. Herein, the \u003cem\u003eb\u003c/em\u003e values at different potentials range from 0.5 to 1 (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb), suggesting the co-existence of diffusion and capacitive controlled processes. In addition, the total capacity could be divided into a diffusion controlled part (\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003ev\u003c/em\u003e\u003csup\u003e1/2\u003c/sup\u003e) and a capacitive controlled one (\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003ev\u003c/em\u003e) at a fixed potential (V) according to the following equations [\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e]:\u003c/p\u003e\n\u003cdiv class=\"Equation\" id=\"Equ3\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003ei(V) = k\u003csub\u003e1\u003c/sub\u003ev\u003csup\u003e1/2\u003c/sup\u003e+k\u003csub\u003e2\u003c/sub\u003ev \u0026nbsp;(3)\u003c/div\u003e\n \u003cdiv class=\"mathdisplay\" name=\"EquationSource\"\u003ei(V) / v\u003csup\u003e1/2\u003c/sup\u003e = k\u003csub\u003e1\u003c/sub\u003e+ k\u003csub\u003e2\u003c/sub\u003ev\u003csup\u003e1/2\u003c/sup\u003e\u0026nbsp; (3)\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eIt can be seen that the capacitive control behavior gradually dominates the total capacity, and the capacitive control contribution increases from 52.3 % at 0.1 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 83.2 % at 2 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec), revealing the superior rate performance of NPC(20Zn-80Co)-600\u0026deg;C.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ed shows the typical GCD curves of NPC(20Zn-80Co)-600\u0026deg;C at the current density of 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for the first three cycles. The initial charging and discharging specific capacity of NPC(20Zn-80Co)-600\u0026deg;C are 804.2 and 1251.9 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with the coulombic efficiency (CE) of 64 %, which is originated from the irreversible processes such as decomposition of electrolyte and the formation of SEI film [\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e]. The influence of calcination temperatures and the initial Zn\u003csup\u003e2+\u003c/sup\u003e/Co\u003csup\u003e2+\u003c/sup\u003e molar ratios on the rate capability are investigated. Fig. S13b shows the rate capability of NPC(40Zn-60Co)-T from 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, it can be observed that NPC(40Zn-60Co)-600\u0026deg;C delivers 786.0, 736.9, 634.9, 521.8, 401.1 and 254.1 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at current density of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. When the current density returns to 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a capacity as high as 783.6 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e still can be achieved. NPC(40Zn-60Co)-600\u0026deg;C has superior rate capability compared with other counterparts, thus proving the optimized calcination temperature of 600\u0026deg;C. Secondly, the rate capability of NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C derived from precursor with different Zn\u003csup\u003e2+\u003c/sup\u003e/Co\u003csup\u003e2+\u003c/sup\u003e molar ratio are displayed in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ee. NPC(20Zn-80Co)-600\u0026deg;C exhibits reversible capacity of 876.5, 768.9, 664.7, 570.7, 480.9 and 352.6 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at current density of 0.1, 0.2, 0.5, 1, 2 and 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, which are higher than other NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C. More importantly, when the current density is back to 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, NPC(20Zn-80Co)-600\u0026deg;C shows a capacity of 857.9 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is closed to the initial specific capacity. The excellent Li\u003csup\u003e+\u003c/sup\u003e storage performance of NPC(20Zn-80Co)-600\u0026deg;C results from the aforementioned high nitrogen content, big specific surface area, suitable porous structure and pore size.\u003c/p\u003e\n\u003cp\u003eFigure S13c and Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ef show the cycling performance of NPC(20Zn-80Co)-600\u0026deg;C at low and high current densities, respectively. NPC(20Zn-80Co)-600\u0026deg;C could retain 98.3 % after 100 cycles at 0.1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 99.8 % after 500 cycles at 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The coulombic efficiencies reach almost 100% after the first cycle, indicating the excellent long-term stability. The charge transfer kinetics of the NPC(\u003cem\u003ex\u003c/em\u003eZn-\u003cem\u003ey\u003c/em\u003eCo)-600\u0026deg;C are further investigated by EIS, it can be noticed from Fig. S13d that the Nyquist plots for all the samples are similar and each curve consists of a semicircle in the high frequency region and an approximate oblique line in the low frequency region. The semicircle of the high frequency region corresponds to the charge transfer resistance (R\u003csub\u003ect\u003c/sub\u003e) generated by the contact between the active material and electrolyte solution, and the contact between the interfacial active material and the copper foil collector fluid. The slant area in the low frequency region represents the Warburg impedance (Z\u003csub\u003ew\u003c/sub\u003e), which is related to the diffusion of Li\u003csup\u003e+\u003c/sup\u003e into the electrode [\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e]. NPC(20Zn-80Co)-600\u0026deg;C exhibits the minimum semicircle compared with that of other NPC, suggesting the minimum charge transfer resistance and Warburg resistance. It could be concluded that the unique hierarchical porous structure with a high specific surface area not only provides a rapid transport channel, but also reduces the transport path of Li\u003csup\u003e+\u003c/sup\u003e. In addition, the as-prepared NPC(20Zn-80Co)-600\u0026deg;C has better Li\u003csup\u003e+\u003c/sup\u003e storage properties compared with other reported porous carbon-based materials (Table S3).\u003c/p\u003e\n\u003cp\u003eMeantime, NPC-(20Zn-80Co)-600\u0026deg;C are also suitable for electrochemical Na\u003csup\u003e+\u003c/sup\u003e storage. Fig. S14a shows the initial three CV curves at scan rate of 0.1 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the first irreversible reduction peak around 0.6 V in the CV curve is mainly caused by the formation of SEI film [\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e] and the peak located around 0 V suggests the sodium ion insertion into NPC(20Zn-80Co)-600\u0026deg;C [\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e]. In addition, the CV curves almost overlapped with each other in the second and third cycles, indicating that NPC(20Zn-80Co)-600\u0026deg;C electrode materials have good cycling performance in the process of Na\u003csup\u003e+\u003c/sup\u003e intercalation/de-intercalation. In addition, a rectangular area can be observed in potential range of 1.5-3 V, suggesting a capacitive behavior [\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e]. Figure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ea illustrates the CV curves of NPC(20Zn-80Co)-600\u0026deg;C at different scan rates ranging from 0.1 to 2.0 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with the similar shape, revealing its high reversibility and good repeatability in the electrochemical reactions. Similar to Li\u003csup\u003e+\u003c/sup\u003e storage, the energy storage mechanism in Na\u003csup\u003e+\u003c/sup\u003e storage is also controlled by both diffusion behavior and capacitance behavior (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eb). As demonstrated in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ec, through quantitative analysis of capacitance control behavior and diffusion control behavior, the behavior of capacitive control accounts for a large part of the total capacity at each scan rate, ranging from 53.9 % (at 0.1 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) to 83.2 % (at 2.0 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), which indicates high proportion of pseudocapacitance of the total capacitance contribution.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ed illustrates the first three GCD curves of NPC(20Zn-80Co)-600\u0026deg;C at a current density of 0.02 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the initial discharging and charging specific capacity are 872.0 and 377.2 mA h g-1, respectively, and the initial coulombic efficiency is 43.3 % (Fig. S14a). NPC(20Zn-80Co)-600\u0026deg;C also presents excellent rate capability and cycling stability. NPC(20Zn-80Co)-600\u0026deg;C delivers reversible capacity of 416.1, 291.6, 245.0, 206.6, 172.7, 144.0, 125.2 and 113.0 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at current densities of 0.02, 0.05, 0.1, 0.2, 0.5, 1, 1.5 and 2 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, which could still retain to 276 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e when the current density immediately returns to 0.02 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. after 450 cycles at 0.05 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, it exhibits a capacity of 218.0 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. S14b), and a reversible specific capacity of 117.8 mA h g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e could be retained after 1000 cycles at high current density of 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ef). In addition, the coulombic efficiency is almost closed to 100% after the first cycle, demonstrating that NPC(20Zn-80Co)-600\u0026deg;C has remarkable long-term cycling stability. The Na\u003csup\u003e+\u003c/sup\u003e storage performance of NPC(20Zn-80Co)-600\u0026deg;C is also comparable with other reported porous carbon-based materials (Table S4).\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn summary, ZnCo-ZIF-derived NPC are prepared by a simple carbonization treatment. The Zn/Co molar ratio within the initial ZnCo-ZIF and the carbonization temeperature are optimized to balance the morphology, nitrogen content, specific surface area and porous structure of the derived NPC. It is found that NPC(20Zn-80Co)-600\u0026deg;C shows excellent electrochemical properties for Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e storage. The as-prepared NPC are expected to be promising alternatives for the application in energy storage and other related fields.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal\u0026nbsp;relationships that could have appeared to influence the work reported in this paper.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge the funding support from the National Natural Science Foundation of China (U1810204), the Natural Science Foundation of Anhui Province (2108085MB45) and the Fundamental Research Funds for the Central Universities (JZ2020HGTB0059, PA2021KCPY0044 and PA2020GDSK0087). We also would like to thank the financial support from the 111 Project (B18018).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eYu ZL, Xin S, You Y, Yu L, Lin Y, Xu DW, Qiao C, Huang ZH, Yang N, Yu SH, Goodenough JB (2016) Ion-catalyzed synthesis of microporous hard carbon embedded with expanded nanographite for enhanced lithium/sodium storage. J Am Chem Soc 138:14915\u0026ndash;14922\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoodenough JB, Park KS (2013) The Li-ion rechargeable battery: a perspective. J Am Chem Soc 135:1167\u0026ndash;1176\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIdota Y, Kubota T, Matsufuji A, Maekawa Y, Miyasaka T (1997) Tin-based amorphous oxide: a high-capacity lithium-ion storage material. 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Nano Lett 12:3783\u0026ndash;3787\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhong J, Yi F, Gao A, Shu D, Huang Y, Li Z, Zhu W, He C, Meng T, Zhao S (2017) Preparation of 3D reduced graphene oxide/MnO\u003csub\u003e2\u003c/sub\u003e nanocomposites through a vacuum-impregnation method and their electrochemical capacitive behavior. ChemElectroChem 4:1088\u0026ndash;1094\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"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},"keywords":"Bimetallic zeolitic imidazolate frameworks, Nitrogen-doped porous carbon, Li-ion battery, Na-ion battery","lastPublishedDoi":"10.21203/rs.3.rs-898776/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-898776/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePorous carbon is regarded as one of the most promising anode candidates for Li-ion battery and Na-ion battery. We herein demonstrate a series of nitrogen-doped porous carbon (NPC) by simply carbonizing bimetallic ZnCo-containing zeolitic imidazolate frameworks (ZnCo-ZIFs). The nitrogen content, specific surface area, pore size distribution and microstructure of prepared NPC are balanced by adjusting Zn\u003csup\u003e2+\u003c/sup\u003e/Co\u003csup\u003e2+\u003c/sup\u003e molar ratio of ZnCo-ZIFs and carbonization process parameters. It is found that the optimized ZnCo-ZIF-derived NPC shows promise for electrochemical Li\u003csup\u003e+\u003c/sup\u003e/Na\u003csup\u003e+\u003c/sup\u003e storage, which could be attributed to the hierarchical porous structure, large specific surface area and relatively high N-doping content.\u003c/p\u003e","manuscriptTitle":"Nitrogen-Doped Porous Carbon Derived From Bimetallic Zeolitic Imidazolate Frameworks For Electrochemical Li+/Na+ Storage","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-09-22 22:22:56","doi":"10.21203/rs.3.rs-898776/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":"7c17d5ba-d04a-4580-8c2a-d7d9ae88f7dc","owner":[],"postedDate":"September 22nd, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":7375693,"name":"Inorganic Chemistry"},{"id":7375694,"name":"Ceramics"}],"tags":[],"updatedAt":"2022-02-12T01:04:41+00:00","versionOfRecord":{"articleIdentity":"rs-898776","link":"https://doi.org/10.1007/s10008-021-05100-y","journal":{"identity":"journal-of-solid-state-electrochemistry","isVorOnly":false,"title":"Journal of Solid State Electrochemistry"},"publishedOn":"2022-01-21 01:04:41","publishedOnDateReadable":"January 21st, 2022"},"versionCreatedAt":"2021-09-22 22:22:56","video":"","vorDoi":"10.1007/s10008-021-05100-y","vorDoiUrl":"https://doi.org/10.1007/s10008-021-05100-y","workflowStages":[]},"version":"v1","identity":"rs-898776","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-898776","identity":"rs-898776","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}

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