Flexible electrode material of carbon nanosphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, preparation method and application thereof

Abstract

The present invention relates to the technical field of electrode material preparation, specifically a flexible electrode material of nano-carbon sphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, its preparation method and application. Nano-needle-shaped manganese-doped nickel cobalt sulfide grows in-situ on the surface of carbon cloth, and each nano-needle is coated with a carbon sphere layer on its surface. In the present invention, a manganese-doped nickel cobalt precursor with controllable morphology is first grown in-situ on carbon cloth. By means of the electrostatic interaction between the anionic negative charge in the precursor and the amino positive charge in dopamine hydrochloride, polydopamine is coated in-situ at room temperature on the surface of the nickel cobalt precursor, and then the target product is obtained through sulfidation and carbonization. The coated carbon sphere layer is beneficial to accelerating the electron conduction rate of nickel cobalt sulfide, providing abundant reaction active sites, accelerating the kinetics of ion transport in the redox reaction process, improving the structural stability of the electrode material and inhibiting the volume expansion of the active substance during cycling, and improving the specific capacitance, rate performance and cycling stability of the electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of electrode materials for solid-state supercapacitors, and particularly relates to a flexible electrode material of nano-carbon sphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, a preparation method thereof, and an application thereof. Background Art

[0002] Due to advantages such as high power density, long cycle durability, and fast charge and discharge capabilities, supercapacitors show broad application prospects in various portable electronic devices, electric vehicles, wearable devices, medical devices, and military fields. Compared with traditional liquid electrolyte supercapacitors, solid-state supercapacitors usually use gel electrolytes, do not generate faults such as electrolyte leakage, and can be integrated in a single chip in various shapes, and are fast energy storage devices for future intelligent wearable electronics fields. Electrode materials are crucial for the performance of supercapacitors. Electrode materials for carbon cloth and carbon fiber-based flexible supercapacitors are expected to be applied to the weaving and integration of clothing due to their light weight, small volume, and strong anti-deformation ability.

[0003] Transition metal nickel cobalt compounds have rich valence electrons due to the presence of vacancies in the outer electrons d orbits of cobalt and nickel, and can perform multi-electron transfer through Faraday redox reactions to improve the charge storage capacity. They are a kind of pseudocapacitive electrode material with great potential. However, their application as electrode materials in supercapacitors is still limited by the following defects: (1) Poor structural stability during long-term charge / discharge cycles due to repeated volume expansion / shrinkage; (2) Lower rate capability, especially affected by low intrinsic conductivity, facing the problem of slow redox reaction kinetics during charge and discharge processes; (3) Poor electron / ion conductivity and lack of redox activity resulting in low energy density limit their application. To solve these problems, introducing nickel cobalt sulfide into a carbon cloth substrate or coating a carbon-based material with high conductivity and high specific surface area on the surface of the active material can significantly increase the conductivity of the electrode material and buffer the volume change of the electrode during charge and discharge, thereby improving its specific capacity and cycle life. Therefore, it is very important to design flexible electrode materials with a reasonable structure, enhanced interfacial charge transfer, and excellent pseudocapacitive activity. Summary of the Invention

[0004] The object of the present invention is to provide a flexible electrode material of carbon nanosphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, and its preparation method and application, so as to solve the defects of poor structural stability, slow redox reaction kinetics process, low conductivity, etc. of transition metal nickel cobalt compounds during long-term charge / discharge cycles; using carbon cloth as a substrate, through hydrothermal reaction, the manganese-doped nickel cobalt precursor is in-situ grown and loaded on the carbon cloth substrate, and polydopamine is in-situ coated on the surface of the manganese-doped nickel cobalt precursor through room-temperature in-situ self-polymerization reaction, and then a flexible electrode material of carbon nanosphere-coated manganese-doped nickel cobalt sulfide / carbon cloth is prepared through hydrothermal sulfidation and calcination processes. The carbon nanosphere layer is beneficial to accelerating the electron conduction rate of nickel cobalt sulfide, providing rich reaction active sites, accelerating the kinetics of ion transport in the redox reaction process, inhibiting the volume expansion of active substances during the cycle, improving the structural stability of the electrode material, and enhancing the specific capacitance, rate performance and cycle stability of the electrode. By simply adjusting the time of coating polydopamine, the thickness of the carbon nanosphere layer can be controlled, and an electrode material with high specific capacitance, good rate performance and excellent cycle stability is prepared for use in a hybrid solid-state flexible supercapacitor.

[0005] The primary object of the present invention is to propose a flexible electrode material of carbon nanosphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, in which the manganese-doped nickel cobalt sulfide grows in-situ on the surface of the carbon cloth, and the manganese-doped nickel cobalt sulfide is in the form of nanoneedles, and each nanoneedle is further coated with a carbon nanosphere layer.

[0006] Furthermore, the diameter of the nanoneedles is 40-100 nm, and the particle size of the carbon nanospheres is 10-50 nm.

[0007] Another object of the present invention is to provide a preparation method of a flexible electrode material of carbon nanosphere-coated manganese-doped nickel cobalt sulfide / carbon cloth, which specifically includes the following steps:

[0008] (1) Pretreat the carbon cloth CC;

[0009] (2) Prepare manganese-doped nickel cobalt precursor / CC: Dissolve hydrated nickel salt, hydrated cobalt salt and hydrated manganese salt in deionized water to obtain a metal ion mixture solution, add urea and ammonium fluoride to the metal ion mixture solution, stir until dissolved to form solution A; Immerse the pretreated carbon cloth CC in step (1) in solution A and let it stand for 4-6 h, then transfer it to a hydrothermal reaction kettle for hydrothermal reaction. After the reaction is completed, it is naturally cooled to room temperature. Take out the reacted carbon cloth, wash it with deionized water, and then dry it to obtain nanoneedle-shaped manganese-doped nickel cobalt precursor in-situ grown on the carbon cloth, denoted as manganese-doped nickel cobalt precursor / CC;

[0010] (3)Preparation of manganese-doped nickel cobalt precursor@PDA / CC: Add tris(hydroxymethyl)aminomethane to an ethanol aqueous solution, dissolve and stir evenly, adjust the pH value of the solution to 8.5, then add dopamine hydrochloride to dissolve it to obtain solution B; put the manganese-doped nickel cobalt precursor / CC obtained in step (2) into solution B, let it stand and react at room temperature for 24 - 96 h, replace solution B every 24 h, take out the reacted carbon cloth, wash it with deionized water, and then dry it to obtain the carbon cloth with polydopamine in-situ coated on the surface of the manganese-doped nickel cobalt precursor, denoted as manganese-doped nickel cobalt precursor@PDA / CC;

[0011] (4)Preparation of manganese-doped nickel cobalt sulfide@PDA / CC: Dissolve sodium sulfide nonahydrate in deionized water to form solution C, immerse the manganese-doped nickel cobalt precursor@PDA / CC obtained in step (3) into solution C and transfer all of it to a hydrothermal reaction kettle for hydrothermal sulfidation reaction. After the reaction is completed, naturally cool it to room temperature, take out the reacted carbon cloth, wash it with deionized water, and then dry it to obtain manganese-doped nickel cobalt sulfide@PDA / CC;

[0012] (5)Preparation of manganese-doped nickel cobalt sulfide@carbon sphere / CC: Calcine the manganese-doped nickel cobalt sulfide@PDA / CC obtained in step (4) under an argon atmosphere, the calcination temperature is 500 - 600 °C, the heating rate is 2 °C / min, and the holding time is 60 - 180 min. After the calcination is completed, naturally cool it to room temperature and then take it out to obtain a flexible electrode material of manganese-doped nickel cobalt sulfide coated with nano-carbon spheres / carbon cloth, denoted as manganese-doped nickel cobalt sulfide@carbon sphere / CC.

[0013] Furthermore, in step (1) of the above preparation method, the pretreatment process of the carbon cloth includes: successively ultrasonically wash the carbon cloth with absolute ethanol and acetone, put it into a drying oven to dry, then immerse it in concentrated sulfuric acid or concentrated nitric acid and let it stand for 4 - 12 h. Take out the immersed carbon cloth, wash it with deionized water multiple times, put it into a drying oven to dry, and finally put it into a muffle furnace, heat it up to 400 - 500 °C, roast it for 2 - 6 h. After the roasting is completed, naturally cool it to room temperature to obtain the pretreated carbon cloth.

[0014] Furthermore, in step (2) of the above preparation method, the hydrated nickel salt is selected from one of nickel nitrate hexahydrate and nickel chloride hexahydrate, the hydrated cobalt salt is selected from one of cobalt nitrate hexahydrate and cobalt chloride hexahydrate, and the hydrated manganese salt is selected as manganese chloride tetrahydrate; the temperature of the hydrothermal reaction is 120 °C and the reaction time is 8 h.

[0015] Furthermore, the molar ratio of hydrated nickel salt, hydrated cobalt salt, hydrated manganese salt, urea, and ammonium fluoride is 1:2:0.5:4:2. The concentration of hydrated nickel salt in solution A is 0.01 - 0.03 mol / L, the concentration of hydrated cobalt salt is 0.02 - 0.06 mol / L, and the concentration of hydrated manganese salt is 0.005 - 0.015 mol / L.

[0016] Furthermore, in step (3) of the above preparation method, the concentration of tris(hydroxymethyl)aminomethane in solution B is 0.01 - 0.03 mol / L, the concentration of dopamine hydrochloride is 0.01 - 0.06 mol / L. The ethanol aqueous solution is obtained by mixing absolute ethanol and water, and the volume ratio of absolute ethanol to water is 1:1 - 1:4.

[0017] Furthermore, in step (4) of the above preparation method, the concentration of sodium sulfide nonahydrate in solution C is 0.2 - 0.6 mol / L, the temperature of the hydrothermal sulfidation reaction is 160 °C, and the reaction time is 6 - 8 h.

[0018] Another object of the present invention is to provide an application of the nano-carbon sphere coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material obtained by the above preparation method as an energy storage electrode material in a supercapacitor. The nano-carbon sphere coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material can be directly used as a working electrode.

[0019] In the above application, using the nano-carbon sphere coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, with an electrolyte of 6 mol / L KOH, at 1 mA / cm 2 the areal specific capacitance of the nano-carbon sphere coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material is 2900 - 4400 mF / cm 2 ; at 30 mA / cm 2 the areal specific capacitance of the nano-carbon sphere coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material is 2200 - 3700 mF / cm 2 , the rate performance is 74 - 85%, and the retention rate of the areal specific capacitance after 5000 cycles is 90 - 98%.

[0020] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the present invention can achieve considerable technical progressiveness and practicality, and has a wide range of utilization values. It has at least the following advantages:

[0021] (1) In the present invention, commercial carbon cloth is pretreated to obtain hydrophilic carbon cloth, and a manganese-doped nickel cobalt precursor with controllable morphology is in-situ grown on the carbon cloth fibers through a one-step hydrothermal reaction. By virtue of the anions (OH- , CO3 2- The electrostatic interaction between the negative charge and the positive charge of the amino group (-NH2) in dopamine hydrochloride enables the in-situ coating of polydopamine on the surface of the manganese-doped nickel-cobalt precursor at room temperature. After sulfidation and carbonization, the target product is obtained. The manganese-doped nickel-cobalt sulfide grows in-situ on the carbon cloth, having the outstanding advantages of light weight, small volume, and strong anti-deformation ability. Moreover, the manganese-doped nickel-cobalt sulfide is firmly combined with the carbon cloth substrate and can be directly used as a working electrode. Compared with the preparation process of powder-like electrode materials, the present invention does not require the mixing of solvents and binders, nor operations such as stirring, coating, and drying, saving the time for electrode preparation. At the same time, it avoids the problems of uneven coating of the electrode material and weak binding between the active material and the substrate during the preparation of the electrode obtained by the traditional preparation method, resulting in the shedding of the active material from the substrate surface during the test and low repeatability and poor stability of the results.

[0022] (2) In the present invention, manganese elements are inserted into the precursor, and the local configuration and electrons around cobalt and nickel atoms are adjusted by manganese doping to form a heterostructure, optimizing the electronic density of states to improve the intrinsic conductivity of nickel-cobalt sulfide, thereby improving the surface electrochemical activity and electron / ion transport of the electrode material.

[0023] (3) The carbon sphere layer, as an excellent conductive substrate, is coated on the surface of the high specific capacity manganese-doped nickel-cobalt sulfide, which can accelerate the electron conduction rate of nickel-cobalt sulfide. At the same time, it can provide abundant reaction active sites, accelerating the diffusion of OH - and Ni 2+ / Co 2+ / Mn 2+ ions and the kinetics of ion transport during the redox reaction between OH - ions, which is beneficial to improving the structural stability of the electrode material and inhibiting the volume expansion of the active substance during the cycle, better exerting the synergistic effect of the high theoretical specific capacity of nickel-cobalt sulfide and the excellent conductivity of the carbon material, and making up for the defects of poor conductivity of nickel-cobalt sulfide and low specific capacity of the carbon material. By adjusting the polydopamine coating time, the thickness of the carbon sphere layer can be effectively controlled, and an energy storage electrode material with the best conductivity and electrochemical active sites can be optimized for synthesis and used in a hybrid solid-state supercapacitor. Compared with the manganese-doped nickel-cobalt sulfide / CC electrode without a carbon sphere layer coating, the manganese-doped nickel-cobalt sulfide@carbon sphere / CC electrode prepared by the present invention has relatively excellent specific capacity and rate performance, can maintain good cycle stability, and can be applied to a hybrid solid-state flexible supercapacitor.

[0024] (4) The preparation method of the present invention is simple and repeatable, with low raw material cost and universality. Description of the Drawings

[0025] Figure 1SEM images of the carbon cloth used in Example 1 before (a) and after (b) the pretreatment in Step (1).

[0026] Figure 2 SEM images of the manganese-doped nickel-cobalt precursor / CC prepared in Step (2) of Example 2 at different magnifications.

[0027] Figure 3 SEM images of the manganese-doped nickel-cobalt sulfide / CC prepared in Step (3) of Comparative Example 1 at different magnifications.

[0028] Figure 4 SEM images of the manganese-doped nickel-cobalt sulfide@PDA / CC prepared in Step (4) of Example 4 at different magnifications.

[0029] Figure 5 SEM images of the manganese-doped nickel-cobalt sulfide@carbon spheres / CC prepared in Step (5) of Example 4 at different magnifications.

[0030] Figure 6 XRD curves of the manganese-doped nickel-cobalt sulfide@carbon spheres / CC prepared in Example 4, the manganese-doped nickel-cobalt sulfide / CC prepared in Comparative Example 1, and the pretreated carbon cloth CC.

[0031] Figure 7 is the XPS survey spectra of the manganese-doped nickel-cobalt sulfide@carbon spheres / CC prepared in Example 4 and the manganese-doped nickel-cobalt sulfide / CC prepared in Comparative Example 1 as electrode materials.

[0032] Figure 8 CV curves of the manganese-doped nickel-cobalt sulfide / CC electrode material prepared in Comparative Example 1 at different scanning rates.

[0033] Figure 9 CV curves of the manganese-doped nickel-cobalt sulfide@carbon spheres / CC electrode material prepared in Example 4 at different scanning rates.

[0034] Figure 10 Comparison diagrams of the galvanostatic charge-discharge (GCD) curves of the electrode materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 at a current density of 1 mA / cm 2 2.

[0035] Figure 11 GCD curves of the manganese-doped nickel-cobalt sulfide@carbon spheres / CC electrode material prepared in Example 4 at different current densities.

[0036] Figure 12 GCD curves of the manganese-doped nickel-cobalt sulfide / CC electrode material prepared in Comparative Example 1 at different current densities.

[0037] Figure 13The specific capacitance retention rate comparison diagram of the manganese-doped nickel-cobalt sulfide@carbon sphere / CC electrode material prepared in Example 4 and the manganese-doped nickel-cobalt sulfide / CC electrode material prepared in Comparative Example 1 during 5000 cycles of charge and discharge at a current density of 5 mA / cm 2 is shown in the figure. Detailed Description of the Invention

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0039] The present invention will be described in detail below with specific embodiments. For those not specified in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The raw materials and reagents used, without indicating the manufacturer, are all conventional products that can be obtained through commercial purchase.

[0040] Example 1:

[0041] (1) Pretreatment of carbon cloth (CC): The carbon cloth with a size of 15×20×0.5 mm 3 was successively ultrasonically washed with absolute ethanol and acetone for 20 min, then placed in a drying oven and dried at 60°C for 12 h. Then it was immersed in a concentrated sulfuric acid solution (the mass fraction of concentrated sulfuric acid is 98%) and allowed to stand for 8 h. After taking out the soaked CC and washing it with deionized water multiple times, it was placed in a drying oven and dried at 60°C for 12 h. Finally, it was placed in a muffle furnace and heated to 450°C at a rate of 5°C / min and calcined for 5 h. After the calcination was completed, it was naturally cooled to room temperature to obtain the pretreated CC.

[0042] (2) Preparation of manganese-doped nickel-cobalt precursor / CC: 0.238 g of nickel chloride hexahydrate, 0.476 g of cobalt chloride hexahydrate, and 0.099 g of manganese chloride tetrahydrate were dissolved in 50 mL of deionized water under stirring to obtain a metal ion mixed solution. 0.24 g of urea and 0.072 g of ammonium fluoride were added to the metal ion mixed solution and stirred until completely dissolved to form solution A. The pretreated CC in step (1) was immersed in solution A and allowed to stand for 4 h, and then all were transferred to a hydrothermal reaction kettle. The hydrothermal reaction kettle was placed in an oven at 120°C for hydrothermal reaction for 8 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The carbon cloth CC reacted in solution A was taken out and washed 3 times with deionized water, and then placed in a vacuum oven and dried at 60°C for 12 h to obtain a nanoneedle-shaped manganese-doped nickel-cobalt precursor grown in-situ on the carbon cloth, denoted as manganese-doped nickel-cobalt precursor / CC.

[0043] (3) Preparation of manganese-doped nickel-cobalt precursor@PDA / CC: Dissolve 0.0726 g of tris(hydroxymethyl)aminomethane in 60 mL of an ethanol-water solution (volume ratio of ethanol to water is 1:1), stir evenly, add ammonia water to adjust the pH value of the solution to 8.5, and then add 0.2 g of dopamine hydrochloride to dissolve it to obtain solution B; put the manganese-doped nickel-cobalt precursor / CC obtained in step (2) into solution B, let it stand at room temperature for 24 h for self-polymerization reaction, take out the carbon cloth CC after reaction in solution B, wash it 3 times with deionized water, and then put it into a vacuum oven and dry it at 60 °C for 12 h to obtain a carbon cloth with polydopamine in-situ coated on the surface of the manganese-doped nickel-cobalt precursor, denoted as manganese-doped nickel-cobalt precursor@PDA / CC.

[0044] (4) Preparation of manganese-doped nickel-cobalt sulfide@PDA / CC: Dissolve 2.4 g of sodium sulfide nonahydrate in 50 mL of deionized water to form solution C, immerse the manganese-doped nickel-cobalt precursor@PDA / CC obtained in step (3) into solution C and transfer all of it to a hydrothermal reaction kettle, place the hydrothermal reaction kettle in an oven at 160 °C for hydrothermal sulfidation reaction for 6 h, after the reaction is completed, naturally cool to room temperature, take out the carbon cloth CC after reaction in solution C, wash it 3 times with deionized water, and then put it into an oven and dry it at 60 °C for 12 h to obtain manganese-doped nickel-cobalt sulfide@PDA / CC.

[0045] (5) Preparation of manganese-doped nickel-cobalt sulfide@carbon sphere / CC: Calcinate and carbonize the manganese-doped nickel-cobalt sulfide@PDA / CC obtained in step (4) under an argon atmosphere, the calcination temperature is 500 °C, the heating rate is 2 °C / min, and the holding time is 120 min. After the calcination is completed, naturally cool to room temperature and take it out to obtain a flexible electrode material of manganese-doped nickel-cobalt sulfide coated with nano-carbon spheres / carbon cloth, denoted as manganese-doped nickel-cobalt sulfide@carbon sphere / CC.

[0046] Use the manganese-doped nickel-cobalt sulfide@carbon sphere / CC prepared in step (5) as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, and perform cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cyclic stability test analysis at different scan rates in a 6 mol / L KOH electrolyte. Calculate the areal specific capacitance at 1 mA / cm 2 as 2987.4 mF / cm 2 at this time, and the areal specific capacitance at 30 mA / cm 2 is 2226.0 mF / cm 2 at this time, the rate performance is 74.5%, and the retention rate of the areal specific capacitance after 5000 cycles is 90.8%.

[0047] Example 2:

[0048] (1) Pretreatment of carbon cloth (CC): The specific operation is the same as step (1) of Example 1.

[0049] (2) Preparation of manganese-doped nickel-cobalt precursor / CC: Replace 0.238 g of nickel chloride hexahydrate and 0.476 g of cobalt chloride hexahydrate with 0.293 g of nickel nitrate hexahydrate and 0.586 g of cobalt nitrate hexahydrate, and the remaining operations are the same as step (2) of Example 1.

[0050] (3) Preparation of manganese-doped nickel-cobalt precursor@PDA / CC: The volume ratio of ethanol to water in the ethanol aqueous solution is 1:2, the self-polymerization reaction time is 48 h, and the fresh solution B is replaced every 24 h. The remaining operations are the same as step (3) of Example 1.

[0051] (4) Preparation of manganese-doped nickel-cobalt sulfide@PDA / CC: The specific operation is the same as step (4) of Example 1.

[0052] (5) Preparation of manganese-doped nickel-cobalt sulfide@carbon sphere / CC: The calcination temperature is 550 °C, and the remaining operations are the same as step (5) of Example 1.

[0053] Take the manganese-doped nickel-cobalt sulfide@carbon sphere / CC prepared in step (5) as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, and perform cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cycle stability test analysis at different scan rates in a 6 mol / L KOH electrolyte. Calculate the areal specific capacitance at 1 mA / cm 2 as 3192.1 mF / cm 2 at, and the areal specific capacitance at 30 mA / cm 2 is 2556.8 mF / cm 2 , the rate performance is 80.1%, and the retention rate of the areal specific capacitance after 5000 cycles is 94.0%.

[0054] Example 3:

[0055] (1) Pretreatment of carbon cloth (CC): Replace concentrated sulfuric acid with concentrated nitric acid with a mass fraction of 68%, and the calcination temperature is 400 °C. The remaining operations are the same as step (1) of Example 1.

[0056] (2) Preparation of manganese-doped nickel-cobalt precursor / CC: Replace 0.238 g of nickel chloride hexahydrate and 0.476 g of cobalt chloride hexahydrate with 0.297 g of nickel nitrate hexahydrate and 0.593 cobalt nitrate hexahydrate. The remaining operations are the same as step (2) of Example 1.

[0057] (3) Preparation of manganese-doped nickel-cobalt precursor@PDA / CC: The volume ratio of ethanol to water in the ethanol aqueous solution is 1:2, the self-polymerization reaction time is 72 h, and the fresh solution B is replaced every 24 h. The remaining operations are the same as those in step (3) of Example 1.

[0058] (4) Preparation of manganese-doped nickel-cobalt sulfide@PDA / CC: The specific operation is the same as that in step (4) of Example 1.

[0059] (5) Preparation of manganese-doped nickel-cobalt sulfide@carbon sphere / CC: The calcination temperature is 600 °C, and the remaining operations are the same as those in step (5) of Example 1.

[0060] Using the manganese-doped nickel-cobalt sulfide@carbon sphere / CC prepared in step (5) as the working electrode, a platinum plate electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cyclic stability test analyses are carried out in a 6 mol / L KOH electrolyte at different scan rates. Based on the GCD curve, the specific area capacitance at 1 mA / cm 2 is 3538.4 mF / cm 2 , and the specific area capacitance at 30 mA / cm 2 is 2905.0 mF / cm 2 , the rate performance is 82.1%, and the retention rate of the specific area capacitance after 5000 cycles is 95.5%.

[0061] Example 4:

[0062] (1) Pretreatment of carbon cloth (CC): The specific operation is the same as that in step (1) of Example 1.

[0063] (2) Preparation of manganese-doped nickel-cobalt precursor / CC: The specific operation is the same as that in step (2) of Example 1.

[0064] (3) Preparation of manganese-doped nickel-cobalt precursor@PDA / CC: The volume ratio of ethanol to water in the ethanol aqueous solution is 1:2, the self-polymerization reaction time is 96 h, and the fresh solution B is replaced every 24 h. The remaining operations are the same as those in step (3) of Example 1.

[0065] (4) Preparation of manganese-doped nickel-cobalt sulfide@PDA / CC: The specific operation is the same as that in step (4) of Example 1.

[0066] (5) Preparation of manganese-doped nickel-cobalt sulfide@carbon sphere / CC: The calcination temperature is 600 °C, and the remaining operations are the same as those in step (5) of Example 1.

[0067] Using the manganese-doped nickel cobalt sulfide@carbon sphere / CC prepared in step (5) as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cyclic stability test analyses were carried out in a 6 mol / L KOH electrolyte at different scan rates. Based on the GCD curve, the specific capacitance per unit area at 1 mA / cm 2 was 4324.1 mF / cm 2 , and at 30 mA / cm 2 it was 3645.0 mF / cm 2 . The rate performance was 84.3%, and the retention rate of the specific capacitance per unit area after 5000 cycles was 97.2%.

[0068] Comparative Example 1:

[0069] (1) Pretreatment of carbon cloth (CC): The specific operation was the same as step (1) of Example 1.

[0070] (2) Preparation of manganese-doped nickel cobalt precursor / CC: The specific operation was the same as step (2) of Example 1.

[0071] (3) Preparation of manganese-doped nickel cobalt sulfide / CC: Dissolve 2.4 g of sodium sulfide nonahydrate in 50 mL of deionized water to form solution C. Immerse the manganese-doped nickel cobalt precursor / CC obtained in step (2) into solution C and transfer it all to a hydrothermal reaction kettle. Carry out hydrothermal sulfidation reaction in an oven at 160 °C for 6 h. After the reaction, naturally cool to room temperature. Take out the carbon cloth CC reacted in solution C, wash it 3 times with deionized water, and then put it into an oven to dry at 60 °C for 12 h to obtain the manganese-doped nickel cobalt sulfide / CC electrode material.

[0072] Using the manganese-doped nickel cobalt sulfide / CC flexible electrode material prepared in step (3) as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cyclic stability test analyses were carried out in a 6 mol / L KOH electrolyte at different scan rates. Based on the GCD curve, the specific capacitance per unit area at 1 mA / cm 2 was 2724.0 mF / cm 2 , and at 30 mA / cm 2 it was 1968.1 mF / cm 2 . The rate performance was 72.3%, and the retention rate of the specific capacitance per unit area after 5000 cycles was 83.5%.

[0073] The above Comparative Example 1 is a manganese-doped nickel-cobalt sulfide / CC flexible electrode material prepared by a two-step hydrothermal reaction, without coating a carbon sphere layer on the surface of the manganese-doped nickel-cobalt compound.

[0074] Comparative Example 2:

[0075] (1) Pretreatment of carbon cloth (CC): The specific operation is the same as step (1) of Example 1.

[0076] (2) Preparation of nickel-cobalt precursor / CC: Dissolve 0.238 g of nickel chloride hexahydrate and 0.476 g of cobalt chloride hexahydrate in 50 mL of deionized water under stirring to obtain a metal ion mixed solution (without manganese ions). Add 0.24 g of urea and 0.072 g of ammonium fluoride to the metal ion mixed solution and stir until completely dissolved to form solution A. The remaining operations are the same as step (2) of Example 1 to obtain nickel-cobalt precursor / CC.

[0077] (3) Preparation of nickel-cobalt precursor@PDA / CC: Dissolve 0.0726 g of tris(hydroxymethyl)aminomethane in 60 mL of an ethanol aqueous solution (volume ratio of ethanol to water is 1:2), stir evenly, add ammonia water to adjust the pH value of the solution to 8.5, and then add 0.2 g of dopamine hydrochloride to dissolve it to obtain solution B; put the nickel-cobalt precursor / CC obtained in step (2) into solution B, let it stand at room temperature for a self-polymerization reaction for 96 h, replace the fresh solution B every 24 h, take out the carbon cloth CC after the reaction in solution B, wash it 3 times with deionized water, and then put it into a vacuum oven and dry it at 60°C for 12 h to obtain a carbon cloth with polydopamine in-situ coated on the surface of the nickel-cobalt precursor, denoted as nickel-cobalt precursor@PDA / CC.

[0078] (4) Preparation of nickel-cobalt sulfide@PDA / CC: The specific operation is the same as step (4) of Example 1, except that the nickel-cobalt precursor@PDA / CC prepared in step (3) of Comparative Example 2 is immersed in solution C (aqueous sodium sulfide solution), and finally nickel-cobalt sulfide@PDA / CC is obtained.

[0079] (5) Preparation of nickel-cobalt sulfide@carbon sphere / CC: Calcine and carbonize the nickel-cobalt sulfide@PDA / CC obtained in step (4) of Comparative Example 2 under an argon atmosphere, the calcination temperature is 600°C, the heating rate is 2°C / min, the holding time is 120 min, and after the calcination is completed, it is naturally cooled to room temperature and taken out to obtain a carbon sphere-coated nickel-cobalt sulfide / CC flexible electrode material, denoted as nickel-cobalt sulfide@carbon sphere / CC.

[0080] The nickel cobalt sulfide@carbon sphere / CC flexible electrode material prepared in step (5) was used as the working electrode, a platinum sheet electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance (EIS), and cyclic stability test analyses were carried out in a 6 mol / L KOH electrolyte at different scanning rates. Based on the GCD curve, the specific area capacitance at 1 mA / cm 2 was 3847.6 mF / cm 2 , and the specific area capacitance at 30 mA / cm 2 was 3093.5 mF / cm 2 . The rate performance was 80.4%, and the retention rate of the specific area capacitance after 5000 cycles was 95.8%.

[0081] The electrode material prepared in Comparative Example 2 above was not doped with manganese element.

[0082] A German ZEISS Sigma 360 scanning electron microscope (SEM) was used to characterize the morphological changes of the intermediate materials and the final electrode materials prepared in the examples and comparative examples. Arbitrarily cut small pieces with a size of 4×4 mm 2 from the prepared flexible electrode, stick them on the conductive glue of the sample stage without distinguishing the front and back, and then spray gold for testing.

[0083] Figure 1 are SEM images of the carbon cloth used in Example 1 before (a) and after (b) the pretreatment in step (1), and the magnification is 5K times. It can be seen that the surface of the carbon cloth fibers was smooth before the pretreatment. After pretreatment by roasting in a concentrated acid solution and an air atmosphere, the surface of the carbon cloth fibers became rough and cracked, which was beneficial to increasing the hydrophilicity of the carbon cloth surface, increasing the loading amount of the active material, and making its combination more firm.

[0084] Figure 2 are SEM images of the manganese-doped nickel cobalt precursor / CC prepared in step (2) of Example 2 at different magnifications. Figure 2 In (a), the magnification is 20k times, Figure 2 and in (b), the magnification is 2k times. Figure 2 It shows that after the hydrothermal reaction in step (2), the nanoneedle-like manganese-doped nickel cobalt precursor grew in-situ and uniformly on the pretreated carbon cloth fibers, and the surface of the nanoneedles was very smooth. The diameter of the nanoneedles was about 40~100 nm.

[0085] Figure 3 are SEM images of the manganese-doped nickel cobalt sulfide / CC prepared in step (3) of Comparative Example 1 at different magnifications. Figure 3 In (a), the magnification is 20k times, Figure 3 and in (b), the magnification is 2k times.Figure 3 It shows that after the ion exchange reaction occurs during the hydrothermal sulfidation process, the generated manganese-doped nickel cobalt sulfide still maintains the nanoneedle morphology and grows uniformly on the carbon cloth fibers, but the surface of the nanoneedles becomes rough.

[0086] Figure 4 Figure 5 is the SEM images of the manganese-doped nickel cobalt sulfide@PDA / CC prepared in step (4) of Example 4 at different magnifications. Figure 4 In (a), the magnification is 1k times. Figure 4 In (b), the magnification is 2k times. Figure 4 In (c), the magnification is 20k times. Figure 4 In (d), the magnification is 100k times. It can be seen from the figure that different from the manganese-doped nickel cobalt sulfide nanoneedles without coated polydopamine in Comparative Example 1 ( Figure 3 ), after coating with polydopamine and then carrying out the hydrothermal sulfidation process, the surface of the nanoneedles is covered with spherical polydopamine particles and the nanoneedles are slightly aggregated.

[0087] Figure 5 Figure 6 is the SEM images of the manganese-doped nickel cobalt sulfide@carbon spheres / CC prepared in step (5) of Example 4 at different magnifications. Figure 5 In (a), the magnification is 1k times. Figure 5 In (b), the magnification is 5k times. Figure 5 In (c), the magnification is 30k times. Figure 5 In (d), the magnification is 100k times. It can be seen from the figure that the manganese-doped nickel cobalt sulfide coated with spherical polydopamine particles still retains the nanoneedle morphology after calcination, grows in-situ on the surface of the carbon cloth, the aggregation phenomenon disappears, and each nanoneedle is coated with a carbon sphere layer on the surface. The diameter of the nanoneedles is about 40 - 100 nm, and the particle size of the carbon spheres is about 10 - 50 nm. The high conductivity and high specific surface area of the carbon sphere layer can increase the contact area between the active material and OH - in the electrolyte, provide more active sites for redox reactions, and play the synergistic effect of the high theoretical specific capacity of the manganese-doped nickel cobalt sulfide and the excellent conductivity of the carbon material, making up for the defects of poor conductivity of nickel cobalt sulfide and low specific capacity of carbon materials.

[0088] XRD tests were carried out using a Rigaku SmartLab SE type X-ray diffractometer produced in Japan. The carbon cloth carrying the active material was placed on the sample stage for analyzing information such as the composition and crystal structure of the material. Figure 6are the XRD curves of the manganese-doped nickel cobalt sulfide@carbon sphere / CC prepared in Example 4, the manganese-doped nickel cobalt sulfide / CC prepared in Comparative Example 1, and the pretreated carbon cloth CC. By comparison, it is found that the XRD curves of the manganese-doped nickel cobalt sulfide@carbon sphere / CC prepared in Example 4 and the manganese-doped nickel cobalt sulfide / CC prepared in Comparative Example 1 both show the characteristic peaks of NiCo2S4 and CC. Among them, 2θ at 26.8°, 31.5°, 38.3°, 50.4°, 55.3°, 65.0°, 69.2° and 78.1° correspond to the (220), (311), (400), (511), (440), (533), (444) and (731) crystal planes of NiCo2S4 respectively. In addition, from the XRD curve of Example 4, it can be seen that there are also diffraction peaks of Co9S8 in the manganese-doped nickel cobalt sulfide@carbon sphere / CC electrode material prepared by the polydopamine coating and calcination process. 2θ at 15.4°, 29.8°, 47.5° and 52.05° correspond to the (111), (311), (511) and (440) crystal planes of Co9S8 respectively, indicating that the loaded nickel cobalt sulfide product contains Co9S8 and NiCo2S4. Due to the small doping amount of manganese element, it is not observed in both the comparative example and Example 4.

[0089] XPS test was carried out using a Thermo Scientific K-Alpha type X-ray photoelectron spectrometer in the United States. The carbon cloth carrying the active material was placed on the sample stage to analyze the valence states of elements and possible bonding effects in the electrode. Figure 7 are the XPS full spectra of the manganese-doped nickel cobalt sulfide@carbon sphere / CC prepared in Example 4 and the manganese-doped nickel cobalt sulfide / CC prepared in Comparative Example 1. Figure 7 It shows that the electrode contains Ni, Co, Mn, S, C, and O elements. However, in Example 4, the N1s energy band appears at 399.1 eV and the intensity of the C1s energy band at 284.8 eV is stronger than that in Comparative Example 1, indicating that the coated polydopamine forms a carbon sphere layer coating on the surface of the manganese-doped nickel cobalt sulfide after calcination.

[0090] A three-electrode test was carried out on the material using a Shanghai Chenhua electrochemical workstation CHI760E. The manganese-doped nickel cobalt sulfide@carbon sphere / CC electrode material prepared in Example 4 or the manganese-doped nickel cobalt sulfide / CC electrode material prepared in Comparative Example 1 was used as the working electrode, a platinum sheet electrode was used as the counter electrode; a Hg / HgO electrode was used as the reference electrode, and cyclic voltammetry (CV) test analysis was carried out at different scan rates in a 6 mol / L KOH electrolyte. Figure 8 and Figure 9 are the CV curves of the electrode materials prepared in Comparative Example 1 and Example 4 at different scan rates. From Figure 8It can be seen that when the scanning rate increases from 2 mV / s to 20 mV / s, the shape of the CV curve of the manganese-doped nickel cobalt sulfide / CC electrode material prepared in Comparative Example 1 can remain consistent. However, when it continues to increase to 50 mV / s and 100 mV / s, the CV curve is severely deformed. Figure 9 In it, when the scanning rate increases from 2 mV / s to 200 mV / s, the shape of the CV curve of the manganese-doped nickel cobalt sulfide@carbon sphere / CC electrode material prepared in Example 4 can still remain consistent, indicating that coating a carbon sphere layer on the surface of manganese-doped nickel cobalt sulfide can improve the rate performance of the electrode.

[0091] Figure 10 Figure is a comparison diagram of the galvanostatic charge-discharge (GCD) curves of the electrode materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 at a current density of 1 mA / cm 2 When the current density is 1 mA / cm 2 , the areal specific capacitances of the electrode materials prepared in Example 1, Example 2, Example 3, Example 4, and Comparative Examples 1 and 2 are 2987.4 mF / cm 2 , 3192.1 mF / cm 2 , 3538.4 mF / cm 2 , 4324.1 mF / cm 2 and 2724.0 mF / cm 2 , 3847.6 mF / cm 2 respectively. Compared with Comparative Example 1 without a carbon sphere layer coating, coating a carbon sphere layer on the surface of manganese-doped nickel cobalt sulfide can significantly improve the specific capacitance of the electrode material. The areal specific capacitance of the electrode material obtained with a coating time of 96 h in Example 4 is the largest, indicating an excellent coating effect. Compared with the nickel cobalt sulfide@carbon sphere / CC prepared by coating polydopamine for 96 h without doping manganese element in Comparative Example 2, the doping of manganese element improves the specific capacitance of the electrode, indicating that the doping of manganese atoms can regulate the local configuration and electrons around nickel and cobalt atoms to form a heterostructure, optimize the electronic density of states, give full play to the synergistic effect between metal ions, and provide rich electrochemically active sites.

[0092] Figure 11 Figure is the GCD curve of the manganese-doped nickel cobalt sulfide@carbon sphere / CC electrode material prepared in Example 4 at different current densities. When the current density is 1 mA / cm 2 , the areal specific capacitance of the electrode material is 4324.1 mF / cm 2 . When the current density increases to 30 mA / cm 2 , the areal specific capacitance of the electrode material is 3645.0 mF / cm 2 , and the rate performance is 84.3%.

[0093] Figure 12 The GCD curves of the manganese-doped nickel cobalt sulfide / CC electrode material prepared in Comparative Example 1 at different current densities. At a current density of 1 mA / cm 2 , the areal specific capacitance of the electrode material is 2724.0 mF / cm 2 . When the current density increases to 30 mA / cm 2 , the areal specific capacitance of the electrode material is 1968.1 mF / cm 2 , and the rate performance is 72.3%.

[0094] Comparing Figure 11 and Figure 12 it can be seen that after coating the carbon sphere layer on the surface of the manganese-doped nickel cobalt sulfide, the excellent conductivity and large specific surface area of the carbon sphere layer can increase the contact area with the electrolyte OH - , provide more redox reaction active sites, and give full play to the synergistic effect of the high theoretical specific capacitance of the manganese-doped cobalt nickel sulfide and the excellent conductivity of the carbon material, significantly improving the areal specific capacitance and rate performance of the prepared electrode.

[0095] Figure 13 The comparison diagram of the specific capacitance retention rate of the electrode materials prepared in Example 4 and Comparative Example 1 during 5000 cycles of charge and discharge at a current density of 5 mA / cm 2 . The capacitance retention rate of the manganese-doped nickel cobalt sulfide@carbon sphere / CC electrode material prepared in Example 4 after 5000 cycles is 97.2%, which is significantly better than the capacitance retention rate of 83.5% of the manganese-doped nickel cobalt sulfide / CC electrode material prepared in Comparative Example 1, indicating that coating the carbon sphere layer can significantly improve the cycling stability of the manganese-doped nickel cobalt sulfide / CC electrode.

[0096] The nano-carbon sphere-coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material disclosed by the present invention uses the pretreated carbon cloth as the substrate. First, a manganese-doped nickel cobalt precursor is in-situ grown on the surface of the carbon cloth through a hydrothermal reaction. Then, room-temperature in-situ coating of polydopamine on the surface of the manganese-doped nickel cobalt precursor is achieved in an ethanol / water solution containing tris(hydroxymethyl)aminomethane and dopamine hydrochloride. Subsequently, a hydrothermal ion exchange reaction occurs to produce a carbon cloth with polydopamine-coated manganese-doped nickel cobalt sulfide. Finally, after a calcination process, the flexible electrode material of carbon cloth with a carbon sphere layer-coated manganese-doped nickel cobalt sulfide is obtained after the decomposition and carbonization of polydopamine. By doping manganese to adjust the local configuration and electrons around cobalt and nickel atoms to form a heterostructure, the present invention can optimize the density of electronic states, improve the intrinsic conductivity of nickel cobalt sulfide, and thus improve the surface electrochemical activity and electron / ion transport of the electrode material. The carbon sphere layer coated on the surface of the manganese-doped nickel cobalt sulfide has high conductivity and a high specific surface area, which can accelerate the electron conduction rate of nickel cobalt sulfide. At the same time, it can provide abundant reactive sites, accelerate the kinetics of ion transport during the redox reaction process, is conducive to improving the structural stability of the electrode material and inhibiting the volume expansion of the active substance during the cycle, and better plays the synergistic effect of the high theoretical specific capacity of nickel cobalt sulfide and the excellent conductivity of the carbon material, making up for the defects of poor conductivity of nickel cobalt sulfide and low specific capacity of the carbon material.

[0097] The above are only embodiments of the present invention and do not impose any formal limitations on the present invention. The present invention can also have other forms of embodiments based on the above structure and function, which will not be listed one by one. Therefore, any person skilled in the art, without departing from the scope of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material, characterized in that: The following steps are involved: (1) Pretreatment of carbon cloth CC; (2) Preparation of manganese-doped nickel-cobalt precursor / CC: dissolving hydrated nickel salt, hydrated cobalt salt and hydrated manganese salt in deionized water to obtain a metal ion mixture, adding urea and ammonium fluoride to the metal ion mixture, stirring until dissolved, and forming solution A; immersing the carbon cloth CC pretreated in step (1) in solution A and standing for 4 to 6 hours, then transferring it to a hydrothermal reactor for hydrothermal reaction, and naturally cooling to room temperature after the reaction, taking out the reacted carbon cloth, washing it with deionized water, and then drying it to obtain a nano-needle-shaped manganese-doped nickel-cobalt precursor grown in situ on the carbon cloth, which is recorded as manganese-doped nickel-cobalt precursor / CC; (3) Preparation of manganese-doped nickel-cobalt precursor @PDA / CC: Add tris(hydroxymethyl)aminomethane to an ethanol aqueous solution and stir to dissolve the mixture, adjust the pH value of the solution to 8.5, and then add dopamine hydrochloride to dissolve the mixture to obtain solution B; place the manganese-doped nickel-cobalt precursor / CC obtained in step (2) into solution B, and allow the mixture to react at room temperature for 24 to 96 h, replace solution B every 24 h, take out the carbon cloth after the reaction, wash it with deionized water, and then dry it to obtain a carbon cloth with polydopamine in situ coated on the surface of the manganese-doped nickel-cobalt precursor, which is recorded as manganese-doped nickel-cobalt precursor @PDA / CC; (4) Preparation of manganese-doped nickel-cobalt sulfide @PDA / CC: dissolving sodium sulfide nonahydrate in deionized water to form a solution C, immersing the manganese-doped nickel-cobalt precursor @PDA / CC obtained in step (3) in the solution C and transferring the whole of the solution into a hydrothermal reactor for a hydrothermal sulfidation reaction. After the reaction is completed, the mixture is naturally cooled to room temperature. The carbon cloth after the reaction is taken out, washed with deionized water, and then dried to obtain manganese-doped nickel-cobalt sulfide @PDA / CC; (5) Preparation of manganese-doped nickel cobalt sulfide@carbon ball / CC: The manganese-doped nickel cobalt sulfide@PDA / CC obtained in step (4) was calcined in an argon atmosphere at a calcination temperature of 500-600°C, a heating rate of 2°C / min, and a holding time of 60-180 min. After the calcination, it was naturally cooled to room temperature and taken out to obtain a nano-carbon ball-coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material, which was recorded as manganese-doped nickel cobalt sulfide@carbon ball / CC.

2. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1, characterized in that: The pretreatment process of the carbon cloth in step (1) includes: ultrasonically washing the carbon cloth with anhydrous ethanol and acetone in sequence, placing it in a drying oven for drying, and then immersing it in concentrated sulfuric acid or concentrated nitric acid for 4 to 12 hours, taking out the soaked carbon cloth and washing it with deionized water for multiple times, placing it in a drying oven for drying, and finally placing it in a Ma Fuel furnace, heating it to 400 to 500° C., roasting it for 2 to 6 hours, and naturally cooling it to room temperature after roasting to obtain the pretreated carbon cloth.

3. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1, characterized in that: The hydrated nickel salt in step (2) is selected from one of nickel nitrate hexahydrate and nickel chloride hexahydrate, the hydrated cobalt salt is selected from one of cobalt nitrate hexahydrate and cobalt chloride hexahydrate, and the hydrated manganese salt is selected from manganese chloride tetrahydrate; the temperature of the hydrothermal reaction is 120° C., and the reaction time is 8 h.

4. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1 or 3, characterized in that: In step (2), the molar ratio of hydrated nickel salt, hydrated cobalt salt, hydrated manganese salt, urea and ammonium fluoride is 1:2:0.5:4:2, the concentration of hydrated nickel salt in solution A is 0.01-0.03 mol / L, the concentration of hydrated cobalt salt is 0.02-0.06 mol / L, and the concentration of hydrated manganese salt is 0.005-0.015 mol / L.

5. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1, characterized in that: In step (3), the concentration of tris(hydroxymethyl)aminomethane in solution B is 0.01 to 0.03 mol / L, the concentration of dopamine hydrochloride is 0.01 to 0.06 mol / L, and the ethanol aqueous solution is obtained by mixing anhydrous ethanol and water, and the volume ratio of anhydrous ethanol to water is 1:1 to 1:

4.

6. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1, characterized in that: In step (4), the concentration of sodium sulfide nonahydrate in solution C is 0.2-0.6 mol / L, the temperature of the hydrothermal sulfidation reaction is 160° C., and the reaction time is 6-8 h.

7. The method for preparing the nano-carbon ball-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material according to claim 1, characterized in that: In the prepared nano-carbon ball-coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material, manganese-doped nickel cobalt sulfide is in situ grown on the surface of the carbon cloth. The manganese-doped nickel cobalt sulfide is in the shape of nanoneedles with a diameter of 40~100nm. The surface of each nanoneedle is coated with a carbon ball layer with a particle size of 10~50nm.

8. Application of the nano-carbon sphere-coated manganese-doped nickel-cobalt sulfide / carbon cloth flexible electrode material obtained by the preparation method as claimed in claim 1 as an energy storage electrode material in a supercapacitor.

9. The use according to claim 8, characterized in that: The nano carbon ball coated manganese-doped nickel cobalt sulfide / carbon cloth flexible electrode material is directly used as a working electrode.

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