Preparation method of NiCo2O4 / C / MnO2 ternary electrode material with nanocage structure

Abstract

The invention relates to the technical field of supercapacitor electrode materials, in particular to a preparation method of a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure. The preparation method comprises the following steps: by taking nickel chloride hexahydrate, sodium citrate dehydrate, potassium hexacyanocobaltate and the like as raw materials, ultrasonically dissolving the raw materials, stirring, standing, aging and the like to obtain a NiCo-PBA nanocube, etching with an ammonia water solution, carbonizing with glucose, soaking with a KMnO4 solution and the like, and finally successfully synthesizing the ternary electrode material with a NiCo2O4 / C / MnO2 hollow nanocage structure. The method is mild in condition and relatively simple and convenient to operate, and the composite electrode material prepared by the preparation method has excellent super-capacitance performance and cycling stability when being used for a supercapacitor electrode; and the capacitance of the electrode material is far higher than that of a common electrode material of a conventional supercapacitor.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor electrode materials technology, and more specifically to a method for preparing a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure. Background Technology

[0002] To address the energy crisis and environmental pollution, the development of renewable and sustainable electrochemical energy storage systems is crucial, and supercapacitors are among the most promising energy storage devices. With their advantages of high power density, fast charging and discharging, long cycle life, and strong environmental adaptability, supercapacitors are playing an increasingly prominent role in transportation (such as hybrid vehicles and rail transit) and portable wearable devices. Their value lies not only in their ability to quickly respond to fluctuations in energy supply and demand, facilitating efficient equipment operation, but also in their ability to work with new energy sources such as wind and solar power to mitigate power generation fluctuations. Furthermore, their production process generates less pollution, and their materials are recyclable, aligning with low-carbon principles and providing strong support for energy transition and the achievement of environmental goals.

[0003] Supercapacitors, with their unique characteristics, have been widely used in numerous fields. These energy storage devices combine high power density, fast charge / discharge rates, and long cycle life, effectively filling the performance gap between traditional capacitors and batteries. Despite these advantages, supercapacitors still face the challenge of relatively lower energy density compared to batteries, which limits their application in scenarios requiring long-term continuous power supply.

[0004] The electrode materials currently used in supercapacitors are relatively insufficient in terms of energy density and their cycle stability is difficult to achieve ideal results. In addition, their energy density is significantly different from the application requirements of large-scale energy storage systems. Therefore, it is necessary to conduct new research and expansion on electrode materials used in supercapacitors, so as to develop products that can solve these existing problems to a certain extent. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, thereby obtaining a novel electrode material to address the shortcomings of current supercapacitor electrode materials. The electrode material prepared using this invention exhibits higher energy density, cycle stability, and conductivity compared to current supercapacitor electrode materials, while also demonstrating excellent practical application feasibility, slow self-discharge characteristics, and extremely low leakage current.

[0006] To achieve the above objectives, the following technical solution is adopted: A method for preparing a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure includes the following steps: Step (1): Dissolve nickel chloride hexahydrate and sodium citrate dihydrate in deionized water by ultrasonication to obtain solution A. Dissolve potassium hexacyanocobaltate in deionized water by ultrasonication to obtain solution B. Under continuous stirring, add solution B dropwise to solution A. After the addition is complete, continue stirring the mixture for more than 5 hours to ensure that the reaction is complete. Then, let the mixture stand for aging for more than 7 days. Finally, centrifuge to collect the precipitate, wash and dry it to obtain NiCo-PBA nanocubes. Step (2): The product powder from step (1) is ultrasonically dispersed in ethanol to form solution C. The ammonia solution is diluted with deionized water to obtain solution D. Under continuous stirring, solution C is added dropwise to solution D and the mixture is stirred for more than 5 hours. Finally, the product is separated by centrifugation, washed and dried to obtain the etched hollow structure NiCo-PBA. Step (3): Dissolve glucose in deionized water to obtain glucose solution, disperse the product obtained in step (2) into the glucose solution, age it at room temperature for more than 24 hours, collect the precipitate by centrifugation, wash and dry it, and finally carbonize the product at 350-400℃ for 2 hours under nitrogen atmosphere to obtain carbon-coated hollow structure NiCo2O4, which is NiCo2O4 / C; Step (4): The NiCo2O4 / C prepared in step (3) is immersed in KMnO4 solution and kept at 60°C for 12 hours. After washing and drying, the target product, NiCo2O4 / C / MnO2 ternary electrode material with nanocage structure, is obtained.

[0007] Furthermore, in step (1), the amount of deionized water used in solution A is 25 mL, the amount of nickel chloride hexahydrate is 0.1-0.2 g, and the amount of sodium citrate dihydrate is 0.15-0.2 g; the amount of deionized water used in solution B is 25 mL, and the amount of potassium hexacyanocobalaminate is 0.1-0.2 g.

[0008] Furthermore, in step (2), the concentration of ammonia solution in solution D is 14 mol / L, the amount is 6 mL, the amount of deionized water is 30 mL, and the amount of ethanol in solution B is 10 mL.

[0009] Furthermore, in step (3), the amount of deionized water used in the glucose solution is 40 mL, and the amount of glucose used is 3-5 g.

[0010] Furthermore, the concentration of the KMnO4 solution in step (4) is 0.01 mol / L.

[0011] Meanwhile, the present invention also provides a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, which is prepared by the above-described preparation method.

[0012] Transition metal compounds possess advantages such as multiple oxidation states, abundant electrochemical active sites, and high theoretical specific capacitance and conductivity. In particular, cobalt-based highly active bimetallic oxides, such as Co-MO (M = Ni, Cu, Zn, and Mn), exhibit variable oxidation states, which can further enhance conductivity, promote electron and ion transfer, and thus improve electrochemical activity. Based on this, the purpose of this invention is to develop an electrode material for supercapacitors based on NiCo2O4 and MnO2, exhibiting higher energy density and better cycle stability, to address the current limitations of supercapacitors.

[0013] Specifically, in the above-described scheme of this invention, hollow NiCo2O4 / C / MnO2 nanocages were successfully obtained through controlled etching and hydrothermal methods using NiCo-PBA nanocubes as precursors. In its unique structure, the hollow NiCo2O4 / C / MnO2 nanocages facilitate electrolyte penetration, provide a large accessible specific surface area, and shorten the ion diffusion path, thereby improving electrochemical kinetic performance. The MnO2 loading introduces a significant pseudocapacitance, greatly enhancing the overall specific capacitance of the electrode material. Based on the synergistic effect of these three components, NiCo2O4 / C / MnO2 exhibits ultra-high capacity characteristics, demonstrating satisfactory energy density and cycle stability. This research provides a new approach for constructing hollow nanocage structures with excellent electrochemical performance, which can be used in next-generation energy storage devices.

[0014] Furthermore, the composite electrode material prepared by the above scheme exhibits satisfactory energy density, cycle stability, and ultra-high energy characteristics of hollow NiCo2O4 / C / MnO2 nanocage supercapacitor electrode material.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The electrode material prepared by the method of the present invention has excellent supercapacitor performance and cycle stability when applied in the field of supercapacitor electrodes. Its capacitance is significantly better than that of various electrode materials widely used in the current field of supercapacitors, and it has a clear competitive advantage in core performance indicators. The preparation method of this invention requires readily available raw materials that do not rely on scarce or high-cost materials. The equipment involved in the preparation process has low cost, and the operation process is simple and easy to implement, which can effectively shorten the production cycle. Based on this, the method has good economic efficiency and operability, laying a solid foundation for its promotion and application in large-scale industrial production. Attached Figure Description

[0016] Figure 1 This is a flowchart of the preparation method of the present invention.

[0017] Figure 2 These are SEM images of the products at different stages in the preparation of the composite electrode material according to the present invention. in: (a) is the SEM image after step (1); (b) is the SEM image after processing in step (3); (c) is the SEM image of the composite electrode material finally prepared in step (4).

[0018] Figure 3 This is a component advantage diagram of the composite electrode material of the present invention (Example 2); in: (ab) Cyclic voltammetry (CV) curves and galvanostatic charge-discharge (GCD) curves of NiCo2O4 / C / MnO2 and NiCo2O4 / C; (cd)CV and GCD curves of NiCo2O4 / C / MnO2; (e) Capacity comparison chart of NiCo2O4 / C and NiCo2O4 / C / MnO2; (f) Electrochemical impedance spectroscopy (EIS) of NiCo2O4 / C and NiCo2O4 / C / MnO2.

[0019] Figure 4 This is a performance characterization diagram of the composite electrode material prepared in Example 2 of the present invention; in: (a) CV curves of NiCo2O4 / C / MnO2 electrode at scan rates of 2-5 mV / s; (b) Linear relationship graph of log(i) and log(v); (cd) The capacitance contribution distribution of NiCo2O4 / C / MnO2 and the ratio of capacitance control to diffusion control; (ef) Detailed CV curves of NiCo2O4 / C / MnO2 and NiCo2O4 / C, and linear fitting curves of scan rate and capacitor current.

[0020] Figure 5 The image shows the electrochemical performance test results of a supercapacitor assembled from the final product of this invention, NiCo2O4 / C / MnO2. in: (a) CV curves of the positive and negative electrodes; (bc) CV performance of asymmetric supercapacitor (ASC) devices under different voltage windows and scan rates; (de) GCD curves and corresponding specific capacitance results under different current densities; (f) Ragoneplot of energy density versus power density. (g) Long-term cycling performance of NiCo2O4 / C / MnO2 / / AC device at a current density of 10A / g; Self-discharge behavior and leakage current characteristics of (hi)NiCo2O4 / C / MnO2 / / AC hybrid devices. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below using specific embodiments.

[0022] This invention provides a method for preparing a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, such as... Figure 1 As shown, the specific steps include: Step (1): Dissolve nickel chloride hexahydrate and sodium citrate dihydrate in deionized water using ultrasonication to obtain solution A. Dissolve potassium hexacyanocobaltate in deionized water using ultrasonication to obtain solution B. Under continuous stirring, add solution B dropwise to solution A. After the addition is complete, continue stirring the mixture for more than 5 hours to ensure that the reaction proceeds fully. Then, let the mixture stand for aging for more than 7 days. Finally, centrifuge to collect the precipitate, wash and dry it to obtain NiCo-PBA nanocubes. The amount of deionized water used in solution A is 25 mL, the amount of nickel chloride hexahydrate is 0.1-0.2 g, and the amount of sodium citrate dihydrate is 0.15-0.2 g. The amount of deionized water used in solution B is 25 mL, and the amount of potassium hexacyanocobaltate is 0.1-0.2 g. Step (2): The product powder from step (1) is ultrasonically dispersed in ethanol to form solution C. The ammonia solution is diluted with deionized water to obtain solution D. Under continuous stirring, solution C is added dropwise to solution D, and the mixture is stirred for more than 5 hours. Finally, the product is separated by centrifugation, washed and dried to obtain the etched hollow structure NiCo-PBA. The concentration of ammonia solution in solution D is 14 mol / L, the amount is 6 mL, the amount of deionized water is 30 mL, and the amount of ethanol in solution B is 10 mL. Step (3): Dissolve glucose in deionized water to obtain a glucose solution. Disperse the product obtained in step (2) into the glucose solution and age it at room temperature for more than 24 hours. Finally, collect the precipitate by centrifugation, wash and dry it. Finally, carbonize the product at 350-400℃ for 2 hours under a nitrogen atmosphere to obtain a carbon-coated hollow structure NiCo2O4, which is NiCo2O4 / C. The amount of deionized water used in the glucose solution is 40 mL, and the amount of glucose is 3-5 g. Step (4): The NiCo2O4 / C prepared in step (3) is immersed in KMnO4 solution with a concentration of 0.01 mol / L and kept at 60°C for 12 hours. After washing and drying, the target product, NiCo2O4 / C / MnO2 ternary electrode material with nanocage structure, is obtained.

[0023] SEM images of the materials at each step of the preparation process are as follows: Figure 2 As shown.

[0024] The following specific examples will be used for further explanation.

[0025] Example 1: Synthesis of NiCo-PBA nanocubes: 0.1 g of nickel chloride hexahydrate and 0.15 g of sodium citrate dihydrate were ultrasonically dissolved in 25 mL of deionized water to form solution A. Separately, 0.1 g of potassium hexacyanocobalaminate was ultrasonically dissolved in 25 mL of deionized water to prepare solution B. Solution B was added dropwise to solution A under continuous stirring. After the addition was complete, the mixture was stirred for another 5 hours to ensure complete reaction. Subsequently, the solution was allowed to stand for 7 days to age, washed three times with deionized water and ethanol, and finally dried at 60 °C to obtain NiCo-PBA nanocubes.

[0026] The prepared NiCo-PBA nanocube powder was ultrasonically dispersed in 10 mL of ethanol to form solution C. 6 mL of 14 mol / L ammonia solution was diluted with 30 mL of deionized water to obtain solution D. Under continuous stirring, solution C was added dropwise to solution D, and the mixture was stirred for more than 5 hours. Finally, the product was separated by centrifugation, washed, and dried to obtain the etched hollow NiCo-PBA nanocages. 4 g of glucose was dissolved in 40 mL of deionized water. The etched hollow NiCo-PBA nanocages were ultrasonically dispersed in the glucose solution and aged at room temperature for more than 24 hours. The precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C. Finally, the product was carbonized at 350-400 °C for 2 hours under a nitrogen atmosphere to obtain carbon-coated hollow NiCo2O4, namely NiCo2O4 / C.

[0027] The prepared NiCo2O4 / C was immersed in a 0.1 mol / L KMnO4 solution, and the in-situ reaction was carried out by taking advantage of the strong oxidizing property of KMnO4 and the reducing property of the carbon layer. The reaction was maintained at 60 °C for 12 hours. After washing and drying, the target product, a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, was obtained.

[0028] Example 2: Synthesis of NiCo-PBA nanocubes: 0.1140 g of nickel chloride hexahydrate and 0.1894 g of sodium citrate dihydrate were ultrasonically dissolved in 25 mL of deionized water to form solution A. Separately, 0.1068 g of potassium hexacyanocobalaminate was ultrasonically dissolved in 25 mL of deionized water to prepare solution B. Solution B was added dropwise to solution A with continuous stirring. After the addition was complete, the mixture was stirred for another 5 hours to ensure complete reaction. Subsequently, the solution was allowed to stand for 7 days without disturbance. The precipitate was collected by centrifugation, washed three times with deionized water and ethanol, and finally dried at 60 °C to obtain NiCo-PBA nanocubes.

[0029] The prepared NiCo-PBA nanocube powder was ultrasonically dispersed in 10 mL of ethanol to form solution C. 6 mL of 14 mol / L ammonia solution was diluted with 30 mL of deionized water to obtain solution D. Under continuous stirring, solution C was added dropwise to solution D, and the mixture was stirred for more than 5 hours. Finally, the product was separated by centrifugation, washed, and dried to obtain the etched hollow NiCo-PBA nanocage.

[0030] 4 g of glucose was dissolved in 40 mL of deionized water. The etched hollow NiCo-PBA nanocages were ultrasonically dispersed in the glucose solution and aged at room temperature for more than 24 hours. The precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C. Finally, the product was carbonized at 350-400 °C for 2 hours under a nitrogen atmosphere to obtain carbon-coated hollow NiCo2O4, namely NiCo2O4 / C.

[0031] The prepared NiCo2O4 / C was immersed in a 0.1 mol / L KMnO4 solution, and the in-situ reaction was carried out by taking advantage of the strong oxidizing property of KMnO4 and the reducing property of the carbon layer. The reaction was maintained at 60 °C for 12 hours. After washing and drying, the target product, a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, was obtained.

[0032] Example 3: Synthesis of NiCo-PBA nanocubes: 0.2 g of nickel chloride hexahydrate and 0.2 g of sodium citrate dihydrate were ultrasonically dissolved in 25 mL of deionized water to form solution A. Separately, 0.2 g of potassium hexacyanocobalaminate was ultrasonically dissolved in 25 mL of deionized water to prepare solution B. Solution B was added dropwise to solution A with continuous stirring. After the addition was complete, the mixture was stirred for another 5 hours to ensure complete reaction. Subsequently, the solution was allowed to stand for 7 days without disturbance. The precipitate was collected by centrifugation, washed three times with deionized water and ethanol, and finally dried at 60 °C to obtain NiCo-PBA nanocubes.

[0033] The prepared NiCo-PBA nanocube powder was ultrasonically dispersed in 10 mL of ethanol to form solution C. 6 mL of 14 mol / L ammonia solution was diluted with 30 mL of deionized water to obtain solution D. Under continuous stirring, solution C was added dropwise to solution D, and the mixture was stirred for more than 5 hours. Finally, the product was separated by centrifugation, washed, and dried to obtain the etched hollow NiCo-PBA nanocage.

[0034] 4 g of glucose was dissolved in 40 mL of deionized water. The etched hollow NiCo-PBA nanocages were ultrasonically dispersed in the glucose solution and aged at room temperature for more than 24 hours. The precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C. Finally, the product was carbonized at 350-400 °C for 2 hours under a nitrogen atmosphere to obtain carbon-coated hollow NiCo2O4, namely NiCo2O4 / C.

[0035] The prepared NiCo2O4 / C was immersed in a 0.1 mol / L KMnO4 solution, and the in-situ reaction was carried out by taking advantage of the strong oxidizing property of KMnO4 and the reducing property of the carbon layer. The reaction was maintained at 60 °C for 12 hours. After washing and drying, the target product, a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, was obtained.

[0036] Comparative Example 1: (1) Synthesis of NiCo-PBA nanocubes: 0.1140 g of nickel chloride hexahydrate and 0.1894 g of sodium citrate dihydrate were ultrasonically dissolved in 25 mL of deionized water to form solution A. Separately, 0.1068 g of potassium hexacyanocobalaminate was ultrasonically dissolved in 25 mL of deionized water to prepare solution B. Solution B was added dropwise to solution A under continuous stirring. After the addition was complete, the mixture was stirred for 5 hours to ensure the reaction proceeded fully. Subsequently, the solution was allowed to stand for 7 days without disturbance. The precipitate was collected by centrifugation, washed three times with deionized water and ethanol, and finally dried at 60 °C to obtain NiCo-PBA nanocubes.

[0037] (2) The prepared NiCo-PBA nanocube powder was ultrasonically dispersed in 10 mL of ethanol to form solution C. 6 mL of 14 mol / L ammonia solution was diluted with 30 mL of deionized water to obtain solution D. Under continuous stirring, solution C was added dropwise to solution D and the mixture was stirred for more than 5 hours. Finally, the product was separated by centrifugation, washed and dried to obtain the etched hollow NiCo-PBA nanocage.

[0038] (3) Dissolve 4g of glucose in 40mL of deionized water, and ultrasonically disperse the etched hollow NiCo-PBA nanocages into the glucose solution. Age at room temperature for 24 hours. Collect the precipitate by centrifugation, wash with deionized water and ethanol, and dry at 60℃. Finally, carbonize the product at 350-400℃ for 2 hours under a nitrogen atmosphere to obtain carbon-coated hollow NiCo2O4, which is NiCo2O4 / C.

[0039] This material was used as the electrode material in Comparative Example 1. Similarly, it was used as the electrode material to prepare electrodes (specifically, this was done on a CHI760E electrochemical workstation).

[0040] Finally, performance tests were conducted on the electrodes of each embodiment and comparative example. The specific performance data from the performance tests of Examples 1-3 and Comparative Examples 1-2 are as follows: Energy density Wh / kg <![CDATA[1Ag -1 Electrode capacitance Fg under certain conditions -1 ]]> Impedance Rct (Ω) <![CDATA[R s (Oh)]]> Example 1 82.7 1450.15 9.56 0.45 Example 2 82.5 1450.20 9.57 0.42 Example 3 82.4 1450.21 9.58 0.41 Comparative Example 1 66.3 912.0 15.25 0.64 Meanwhile, the electrode capacitance of Example 2, Comparative Example 1, and Comparative Example 2 were tested separately under different conditions, and the results are as follows: Electrochemical testing conditions <![CDATA[1Ag -1 ]]> <![CDATA[2Ag -1 ]]> <![CDATA[3Ag -1 ]]> <![CDATA[5Ag -1 ]]> <![CDATA[8Ag -1 ]]> <![CDATA[10Ag -1 ]]> Comparative Example 1 912.0 908.2 791.3 685.3 560.5 380.2 Example 2 1450.2 1334.9 1132.5 1089.8 833.7 716.0 The data tests were conducted on the optimal Example 2 and Comparative Example 1.

[0041] The method of this invention is obtained by reducing KMnO4 based on Comparative Example 1. Transition metal compounds have advantages such as multiple oxidation states, abundant electrochemical active sites, high theoretical specific capacitance and conductivity, etc., according to the appendix... Figure 3 It is evident that the MnO2 loading introduces a significant pseudocapacitance, which greatly improves the overall specific capacitance of the electrode material. The energy density of the example is above 82.5 Wh / kg, and the electrode capacitance is greater than 1450.2 F / g, both of which are superior to the electrode capacitance of the comparative example of 912.0 F / g.

[0042] Tests conducted on various embodiments and comparative examples show that: The electrode prepared by the method of the present invention has significant performance advantages compared with the intermediate material.

[0043] The energy density of each embodiment of the present invention reaches 82.5 Wh / kg or higher; 1 Ag -1 Under these conditions, the electrode capacitance reached over 1450.2 F / g; the impedance Rct (Ω) was over 9.57; the impedance R s (Ω) is above 0.42.

[0044] The energy density of Comparative Example 1 was only 66.3 Wh / kg; 1 Ag -1Under these conditions, the electrode capacitance reached over 912.0 F / g; the impedance Rct (Ω) was over 15.25, and the impedance R s (Ω) are all above 0.64.

[0045] Based on the above performance data and the appendix Figure 4 Further comparisons were made of the enhanced electrochemical performance of the NiCo2O4 / C / MnO2 electrode. The mixed NiCo2O4 / C / MnO2 electrode exhibits the best charge-discharge channels and abundant ion transport channels, clearly demonstrating a significant improvement in the performance of the composite electrode material.

[0046] Furthermore, when assembling an HSC device based on NiCo2O4 / C / MnO2, at 800Wkg -1 The energy density at that time was 82.5 Wh / kg, according to the attached... Figure 5 It is evident that after more than 8000 cycles, the initial capacitance retention rate still reaches 70.5%, demonstrating excellent cycle performance. After prolonged cycling, the coulombic efficiency remains around 100%, indicating that the charge-discharge process is highly reversible.

[0047] This invention utilizes NiCo-PBA nanocubes as a precursor to successfully obtain a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure via controlled etching and hydrothermal methods. The electrode material of the preferred embodiment 2 exhibits a capacitance of 1450.2 F / g at a current density of 1 A / g. This electrochemical performance can be attributed to the large specific surface area and abundant electrochemical activity of NiCo2O4 / C / MnO2. The above comparative results fully demonstrate that the composite electrode material prepared by the method of this invention has excellent performance. The problems of low energy density and cycle stability of the electrode material are fully solved by the method of this invention, which is attributed to the effect of gradually preparing three different component structures on carbon fiber cloth through different steps in the preparation method of this invention.

[0048] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a NiCo2O4 / C / MnO2 ternary electrode material with a nanocage structure, characterized in that: Includes the following steps: Step (1): Dissolve nickel chloride hexahydrate and sodium citrate dihydrate in deionized water by ultrasonication to obtain solution A. Dissolve potassium hexacyanocobaltate in deionized water by ultrasonication to obtain solution B. Under continuous stirring, add solution B dropwise to solution A. After the addition is complete, continue stirring the mixture for more than 5 hours to ensure that the reaction is complete. Then, let the mixture stand for aging for more than 7 days. Finally, centrifuge to collect the precipitate, wash and dry to obtain NiCo-PBA nanocubes. Step (2): The product powder from step (1) is ultrasonically dispersed in ethanol to form solution C. The ammonia solution is diluted with deionized water to obtain solution D. Under continuous stirring, solution C is added dropwise to solution D and the mixture is stirred for more than 5 hours. Finally, the product is separated by centrifugation, washed and dried to obtain the etched hollow structure NiCo-PBA. Step (3): Dissolve glucose in deionized water to obtain glucose solution, disperse the product obtained in step (2) into the glucose solution, age it at room temperature for more than 24 hours, collect the precipitate by centrifugation, wash and dry it, and finally carbonize the product at 350-400℃ for 2 hours under nitrogen atmosphere to obtain carbon-coated hollow structure NiCo2O4, which is NiCo2O4 / C; Step (4): The NiCo2O4 / C prepared in step (3) is immersed in KMnO4 solution and kept at 60°C for 12 hours. After washing and drying, the target product, NiCo2O4 / C / MnO2 ternary electrode material with nanocage structure, is obtained.

2. The preparation method according to claim 1, characterized in that: In step (1), the amount of deionized water used in solution A is 25 mL, the amount of nickel chloride hexahydrate is 0.1-0.2 g, and the amount of sodium citrate dihydrate is 0.15-0.2 g; the amount of deionized water used in solution B is 25 mL, and the amount of potassium hexacyanocobalaminate is 0.1-0.2 g.

3. The preparation method according to claim 1, characterized in that: In step (2), the concentration of ammonia solution in solution D is 14 mol / L, the volume is 6 mL, the volume of deionized water is 30 mL, and the volume of ethanol in solution B is 10 mL.

4. The preparation method according to claim 1, characterized in that: In step (3), the amount of deionized water used in the glucose solution is 40 mL, and the amount of glucose used is 3-5 g.

5. The preparation method according to claim 1, characterized in that: The concentration of the KMnO4 solution in step (4) is 0.01 mol / L.

6. A ternary electrode material with a nanocage structure of NiCo2O4 / C / MnO2, characterized in that: It is prepared by the preparation method described in any one of claims 1-5.

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