Nitrogen-doped porous nanocarbon material, capacitor electrode material, capacitor electrode, preparation method thereof and supercapacitor

Abstract

The application relates to the field of electrochemical energy storage technology and discloses a nitrogen-doped porous nanocarbon material, wherein the nanocarbon material has microporous structure and mesoporous structure, the BET specific surface area of the nanocarbon material is 300-3000 m 2 / g, the proportion of the specific surface area in micropores in the total specific surface area is higher than 60%; the total pore volume of the nanocarbon material is 0.5-2 cm 3 / g, the proportion of the pore volume in micropores in the total pore volume is higher than 50%; the mass percentage of surface carbon of the nanocarbon material is 70-95% measured by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 1-20%; and the nanocarbon material has a sheet-like appearance. The preparation method can realize high nitrogen doping, catalytic graphitization and activation pore-forming of the nanocarbon material at the same time. When the nitrogen-doped nanocarbon material is applied to a supercapacitor and a water-based alkaline electrolyte is used, the specific capacitance of a single electrode can be up to 252 F / g at a current density of 1 A / g, and the nanocarbon material exhibits excellent capacitive performance.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to nitrogen-doped porous carbon nanomaterials, capacitor electrode materials, capacitor electrodes and their preparation methods, and supercapacitors. Background Technology

[0002] With the continuous development and utilization of clean and renewable energy sources such as solar, wind, and tidal energy, energy storage devices, including lithium-ion batteries and supercapacitors, have made significant progress in recent years, with a substantial increase in energy density. Supercapacitors, as a new type of green energy storage device positioned between traditional capacitors and batteries, feature short charging times, long lifespans, good temperature characteristics, energy conservation, and environmental friendliness. While supercapacitors have high power density and are suitable for high-current charging and discharging, their energy density is relatively low. Therefore, to improve the overall performance of supercapacitors, researchers have explored two aspects: research on novel electrode materials and the development of hybrid supercapacitors, including lithium-ion capacitors. Currently, commonly used electrode materials include carbon materials, transition metal oxides, hydroxides, and conductive polymers. Among these, carbon materials have high stability and low cost, and are widely used in both electric double-layer supercapacitors and lithium-ion capacitors.

[0003] Currently, the most widely used material in supercapacitors is super-activated carbon synthesized from raw materials such as biomass and petroleum coke. Super-activated carbon has a high specific surface area and a large number of microporous structures, exhibiting excellent specific capacitance and high specific capacity. However, the disordered structure of activated carbon makes the ion transport channels tortuous and its own conductivity poor. Therefore, porous carbon materials with a more regular structure and a certain degree of graphitization have become one of the research hotspots. In addition, the incorporation of heteroatoms such as nitrogen and oxygen can effectively improve the conductivity and wettability of carbon materials, and pseudocapacitance can be introduced through the redox reaction between heteroatoms and electrolyte, thereby improving the overall capacity of the material. At present, there are several main methods for preparing nitrogen-doped porous carbon materials. One method is to use nitrogen-containing biomass as raw material, carbonize it, and then activate it with potassium hydroxide to obtain high specific surface area, porous, nitrogen-doped nanocarbon materials. Another method is to obtain nitrogen-doped nanomaterials by pyrolysis of nitrogen-containing polymers or nitrogen-containing organic acid salts and then acid washing. Based on reported literature and published patents, both methods produce nano-carbon materials with porous structures and can achieve high nitrogen doping, but the capacitance performance of the materials needs to be improved. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of poor capacitance performance of porous carbon nanomaterials in the prior art, and to provide a nitrogen-doped porous carbon nanomaterial, a capacitor electrode material, a capacitor electrode, a method for preparing the same, and a supercapacitor. The method provided by this invention can achieve nitrogen doping of carbon nanomaterials simply and efficiently. The prepared carbon nanomaterial has a high specific surface area and a large number of microporous structures, and exhibits excellent capacitance performance when applied to supercapacitors.

[0005] To achieve the above objectives, the first aspect of the present invention provides a nitrogen-doped porous carbon nanomaterial, wherein the carbon nanomaterial has a microporous structure and a mesoporous structure, and the BET specific surface area of ​​the carbon nanomaterial is 300-3000 m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 60%; the total pore volume of the nano-carbon material is 0.5-2cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 50%; the mass percentage of carbon on the surface of the nano-carbon material is 70-95% and the mass percentage of nitrogen is 1-20% as determined by X-ray photoelectron spectroscopy; the nano-carbon material has a sheet-like morphology.

[0006] A second aspect of this invention provides a method for preparing nitrogen-doped carbon nanomaterials, the method comprising the following steps:

[0007] (1) Precursor preparation: A nickel source, a nitrogen-containing organic acid and a potassium source are mixed with a solvent to form a homogeneous solution, and then the solvent in the homogeneous solution is removed to obtain a precursor material. The nitrogen-containing organic acid is ethylenediaminetetraacetic acid and / or 2,5-pyridinedicarboxylic acid, and the potassium source is selected from one or more of potassium carbonate, potassium bicarbonate and potassium hydroxide.

[0008] (2) Calcination: Under an inert atmosphere, the precursor material obtained in step (1) is calcined to obtain pyrolysis products;

[0009] (3) Acid washing: Provide an aqueous solution containing the pyrolysis product obtained in step (2) and react it with acid, then separate the solid and liquid, wash and dry.

[0010] A third aspect of the present invention provides a capacitor electrode material comprising an active substance, a conductive agent, and a binder, wherein the active substance is the nitrogen-doped nanocarbon material described in the first aspect or a nitrogen-doped nanocarbon material prepared according to the preparation method described in the second aspect.

[0011] A fourth aspect of the present invention provides a capacitor electrode, the electrode comprising a current collector and an electrode material coated and / or filled on the current collector, wherein the electrode material is the electrode material described in the third aspect.

[0012] The fifth aspect of the present invention provides a method for preparing a capacitor electrode, the method comprising coating and / or filling a slurry containing an active material, a conductive agent, a binder, and a solvent onto a current collector, drying, and calendering or not calendering, wherein the active material is the nitrogen-doped nano-carbon material described in the first aspect or the nitrogen-doped nano-carbon material prepared according to the preparation method described in the second aspect.

[0013] The sixth aspect of the present invention provides a supercapacitor comprising an electrode core and an electrolyte, wherein the electrode core and the electrolyte are sealed within a battery casing, the electrode core comprising an electrode and a separator, and the electrode being either the capacitor electrode described in the fourth aspect or a capacitor electrode prepared according to the preparation method described in the fifth aspect.

[0014] Through the above technical solution, the present invention has the following advantages:

[0015] (1) The nitrogen-doped porous carbon nanomaterials provided by this invention have a sheet-like morphology and possess microporous and mesoporous structures, with a BET specific surface area of ​​300-3000 m². 2 / g, the proportion of microporous specific surface area to total specific surface area is higher than 60%; the total pore volume is 0.5-2cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 50%; the mass percentage of carbon on the surface of the nano-carbon material, as measured by X-ray photoelectron spectroscopy, is 70-95%, and the mass percentage of nitrogen is 1-20%; the nitrogen-doped porous nano-carbon material provided by this invention has high nitrogen doping, high specific area and a large number of micropore structures, and can be applied to supercapacitors.

[0016] (2) In the method for preparing nitrogen-doped carbon nanomaterials provided by the present invention, precursor materials are prepared using nitrogen-containing organic acids, nickel sources, and potassium sources. During the high-temperature calcination of the precursor materials, high nitrogen doping, catalytic graphitization, and activated pore formation of the carbon nanomaterials can be achieved simultaneously. This preparation process is simple and easy to produce. The preparation method of the present invention can achieve different nitrogen doping contents by controlling the proportion of nitrogen-containing organic acids, and can obtain porous carbon nanomaterials with sheet-like morphology by changing the proportion of potassium sources.

[0017] (3) When the nitrogen-doped porous carbon nanomaterial provided by the present invention is applied to a supercapacitor, the single electrode specific capacitance can reach up to 252 F / g when using an aqueous alkaline electrolyte at a current density of 1 A / g, showing excellent capacitance performance. Attached Figure Description

[0018] Figure 1 This is a transmission electron microscope image of the nitrogen-doped carbon nanomaterial prepared in Example 1;

[0019] Figure 2This is the N2 adsorption-desorption isotherm of the nitrogen-doped carbon nanomaterial prepared in Example 1;

[0020] Figure 3 This is a complete scan XPS image of the nitrogen-doped carbon nanomaterial prepared in Example 1;

[0021] Figure 4 This is the high-resolution XPS N1s spectrum of the nitrogen-doped carbon nanomaterial prepared in Example 1;

[0022] Figure 5 This is the Raman spectrum of the nitrogen-doped carbon nanomaterial prepared in Example 1;

[0023] Figure 6 The cyclic voltammetry curves of the nitrogen-doped carbon nanomaterials prepared in Example 1 at different scan rates in an aqueous alkaline electrolyte are shown.

[0024] Figure 7 The figures show the constant current charge-discharge curves of the nitrogen-doped carbon nanomaterials prepared in Example 1 at different current densities in an aqueous alkaline electrolyte. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of this invention provides a nitrogen-doped porous carbon nanomaterial, wherein the carbon nanomaterial has a microporous structure and a mesoporous structure, and the BET specific surface area of ​​the carbon nanomaterial is 300-3000 m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 60%; the total pore volume of the nano-carbon material is 0.5-2cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 50%; the mass percentage of carbon on the surface of the nano-carbon material is 70-95% and the mass percentage of nitrogen is 1-20% as determined by X-ray photoelectron spectroscopy; the nano-carbon material has a sheet-like morphology.

[0027] In this invention, the term "mesopore" is defined as a pore with a diameter in the range of 2-50 nm. A pore with a diameter less than 2 nm is defined as a "micropore".

[0028] In some embodiments of the present invention, the BET specific surface area of ​​the nano-carbon material is 300-3000 m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 60%, preferably, the BET specific surface area of ​​the nano-carbon material is 1000-2000m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 75%.

[0029] In some embodiments of the present invention, the total pore volume of the nano-carbon material is 0.5-2 cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 50%, preferably, the total pore volume of the nanocarbon material is 0.7-1.5cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 60%.

[0030] In this invention, the pore structure properties of the material are detected using the BET test method. Specifically, a Quantachrome AS-6B analyzer is used for measurement, and the specific surface area and pore volume of the material are obtained by the Brunauer-Emmett-Taller (BET) method.

[0031] In some embodiments of the present invention, the mass percentage of carbon on the surface of the nano-carbon material, as measured by X-ray photoelectron spectroscopy, is 70-95%, and the mass percentage of nitrogen is 1-20%; preferably, the mass percentage of carbon on the surface of the nano-carbon material, as measured by X-ray photoelectron spectroscopy, is 80-95%, and the mass percentage of nitrogen is 2-15%.

[0032] In this invention, the term "nitrogen-doped nanocarbon material" refers to the element nitrogen. Specifically, this term refers to the nitrogen element present on the surface of the material in various forms during the preparation process of nitrogen-doped nanocarbon material.

[0033] In some embodiments of the present invention, preferably, the nitrogen-doped carbon nanomaterial may also contain oxygen, which may be present on the surface of the material in various forms during the preparation process of the nitrogen-doped carbon nanomaterial. Preferably, the mass percentage of oxygen on the surface of the carbon nanomaterial, as measured by X-ray photoelectron spectroscopy, is 3-15%, more preferably 5-11%.

[0034] In some embodiments of the present invention, the nitrogen-doped carbon nanomaterial may contain various doping elements known to those skilled in the art that can be applied to carbon materials. Preferably, the nitrogen-doped carbon nanomaterial does not contain elements such as nickel, potassium, sulfur, boron, phosphorus, fluorine, chlorine, bromine, and iodine.

[0035] In this invention, the carbon, nitrogen, and oxygen content on the surface of the nitrogen-doped carbon nanomaterial was determined by X-ray photoelectron spectroscopy (XPS). The XPS analysis was performed on an ESCALab250 XPS spectrometer from Thermo Scientific equipped with ThermoAvantage V5.926 software. The excitation source was monochromatic AlKα X-rays with an energy of 1486.6 eV and a power of 150 W. The narrow scan passthrough energy was 30 eV, and the baseline vacuum during analysis was 6.53 × 10⁻⁶. -9 mbar, electron binding energy was corrected using the C1s peak (284.6 eV) of elemental carbon, and data processing was performed on Thermo Avantage software. Quantitative analysis was conducted using the sensitivity factor method in the analysis module. Before testing, the material was dried in a helium atmosphere at 150°C and 1 standard atmosphere for 3 hours.

[0036] In some embodiments of the present invention, preferably, the nanocarbon material has a porous sheet-like structure. The morphology of the nanocarbon material can be determined by transmission electron microscopy.

[0037] In some embodiments of the present invention, preferably, the ratio of the intensity of the D peak to the intensity of the G peak in the Raman curve of the nano-carbon material (i.e., Ig) is... G / I D The concentration of the carbon nanomaterial is 0.5-1.5, preferably 0.7-1.1. The nano-carbon material of the present invention has obvious D and G peaks, a certain degree of graphitization, and by transmission electron microscopy, it can be observed that the nano-carbon material of the present invention not only has a porous sheet-like structure, but also has a graphitized carbon layer.

[0038] In this invention, the term "graphitized carbon layer" refers to a carbon structure in which a layered structure can be clearly observed under a transmission electron microscope, rather than an amorphous structure.

[0039] A second aspect of this invention provides a method for preparing nitrogen-doped carbon nanomaterials, the method comprising the following steps:

[0040] (1) Precursor preparation: A nickel source, a nitrogen-containing organic acid and a potassium source are mixed with a solvent to form a homogeneous solution, and then the solvent in the homogeneous solution is removed to obtain a precursor material. The nitrogen-containing organic acid is ethylenediaminetetraacetic acid and / or 2,5-pyridinedicarboxylic acid, and the potassium source is selected from one or more of potassium carbonate, potassium bicarbonate and potassium hydroxide.

[0041] (2) Calcination: Under an inert atmosphere, the precursor material obtained in step (1) is calcined to obtain pyrolysis products;

[0042] (3) Acid washing: Provide an aqueous solution containing the pyrolysis product obtained in step (2) and react it with acid, then separate the solid and liquid, wash and dry.

[0043] In some embodiments of the present invention, the method for preparing the nitrogen-doped nano-carbon material uses a nitrogen-containing organic acid as a carbon source and a nitrogen source, a potassium source as an activator, and a nickel source as a catalyst to prepare a precursor material. During the preparation process, the nickel source and the nitrogen-containing organic acid first form a complex (i.e., the precursor material), and then the precursor material is pyrolyzed in a high-temperature inert atmosphere. In this process, the nitrogen-containing organic acid, as a carbon source and a nitrogen source, can achieve a high nitrogen doping amount in the material, while the potassium source can play a role in activating and creating pores. Preferably, the catalytic effect of the nickel source can also improve the graphitization degree of the material. Finally, the nickel and potassium elements in the material are removed by acid washing to obtain the nitrogen-doped porous nano-carbon material. The preparation method of this invention can simultaneously achieve high nitrogen doping, catalytic graphitization, and activated pore formation of nano-carbon materials. By controlling the proportion of nitrogen-containing organic acids, different nitrogen doping contents can be achieved. Furthermore, by changing the proportion of the potassium source, porous nano-carbon materials with a sheet-like morphology can be obtained. The prepared nitrogen-doped nano-carbon materials possess both microporous and mesoporous structures, and the BET specific surface area of ​​the nano-carbon materials is 300-3000 m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 60%; the total pore volume of the nano-carbon material is 0.5-2cm³. 3 / g, the micropore volume accounts for more than 50% of the total pore volume; the mass percentage of carbon on the surface of the nano-carbon material, as measured by X-ray photoelectron spectroscopy, is 70-95%; the mass percentage of nitrogen is 1-20%. The method provided by this invention can simply and efficiently achieve nitrogen doping of nano-carbon materials. Furthermore, thanks to the catalytic effect of the nickel source and the pore-forming activation effect of the potassium source, the prepared nano-carbon material has a high specific surface area and a large number of microporous structures. Preferably, the nano-carbon material also contains a graphitized carbon layer.

[0044] In some embodiments of the present invention, the method for forming the homogeneous solution is not particularly limited. For example, it can be formed by heating, and more preferably by heating and stirring. The present invention also does not particularly limit the heating temperature and the stirring rate, as long as the method is sufficient to form the homogeneous solution.

[0045] In some embodiments of the present invention, preferably, in step (1), the precursor material is obtained by dissolving a nickel source, a nitrogen-containing organic acid, and a potassium source in a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution. There is no particular limitation on the type of solvent, as long as it can form a homogeneous solution; for example, the solvent can be water, ethanol, etc., preferably water. There is also no particular limitation on the amount of solvent used, again as long as it can form a homogeneous solution. The solvent in the homogeneous solution can be removed by direct evaporation. The evaporation temperature and process can employ existing techniques known to those skilled in the art; for example, drying in an oven can remove the solvent from the homogeneous solution.

[0046] In some embodiments of the present invention, in step (1), the nickel source can be a nickel-containing inorganic salt commonly used in the art. Preferably, the nickel source is selected from one or more of basic nickel carbonate, nickel acetate, nickel chloride and nickel nitrate, with basic nickel carbonate being the most preferred.

[0047] In some embodiments of the present invention, preferably, the nitrogen-containing organic acid is ethylenediaminetetraacetic acid and / or 2,5-pyridinedicarboxylic acid, more preferably ethylenediaminetetraacetic acid.

[0048] In some embodiments of the present invention, the potassium source is selected from one or more of potassium carbonate, potassium bicarbonate and potassium hydroxide, preferably potassium hydroxide.

[0049] In some embodiments of the present invention, preferably, the molar ratio of the nickel source, the nitrogen-containing organic acid, and the potassium source, calculated as nickel element, is 1:1-10:0.1-10, more preferably 1:1-5:0.5-2, and even more preferably 1:1:1. This preferred embodiment is more advantageous for obtaining a high specific surface area.

[0050] In some embodiments of the present invention, preferably, in step (2), the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium, preferably a nitrogen atmosphere and / or an argon atmosphere.

[0051] In some embodiments of the present invention, preferably, the calcination method includes: heating to 400-1000°C at a heating rate of 2-10°C / min, preferably heating to 600-800°C at a heating rate of 5-10°C / min, calcining at a constant temperature for 1-8 hours, preferably 2-4 hours, and then cooling to room temperature at a cooling rate of 1-10°C / min, preferably 3-5°C / min.

[0052] In some embodiments of the present invention, preferably, in step (3), the pickling can be carried out using various inorganic acids and / or organic acids, as long as they can remove nickel and potassium elements from the pyrolysis products. For example, the acid used for pickling can be selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and acetic acid, preferably concentrated hydrochloric acid. There are no special requirements on the amount of acid used, as long as it can remove nickel and potassium elements from the material. To better remove nickel and potassium elements from the material, preferably, an excess of acid is used during pickling.

[0053] In some embodiments of the present invention, preferably, the pickling temperature is 80-120°C, more preferably 90-100°C; and the contact reaction time is 6-24 hours, more preferably 8-12 hours.

[0054] In some embodiments of the present invention, the washing is used to remove acid residues on the nitrogen-doped carbon nanomaterials caused by the acid washing process. Therefore, various water washing methods that can wash the nitrogen-doped carbon nanomaterials to neutrality are applicable to the present invention.

[0055] In some embodiments of the present invention, drying is used to remove water from nitrogen-doped carbon nanomaterials. Drying can be performed under normal pressure or reduced pressure. Drying conditions may include a temperature of 100-120°C and a time of 6-10 hours.

[0056] In some embodiments of the present invention, preferably, the amounts of the nickel source, nitrogen-containing organic acid, and potassium source are such that the mass percentage of carbon on the surface of the nitrogen-doped nanocarbon material is 70-95%, and the mass percentage of nitrogen is 1-20%.

[0057] In some embodiments of the present invention, preferably, the amounts of the nickel source, nitrogen-containing organic acid, and potassium source are such that the mass percentage of carbon on the surface of the nitrogen-doped nanocarbon material is 80-95%, and the mass percentage of nitrogen is 2-15%.

[0058] In some embodiments of the present invention, the nitrogen-doped carbon nanomaterial may contain various doping elements known to those skilled in the art that can be applied to carbon materials. Preferably, the nitrogen-doped carbon nanomaterial does not contain elements such as nickel, potassium, sulfur, boron, phosphorus, fluorine, chlorine, bromine, and iodine.

[0059] A third aspect of the present invention provides a capacitor electrode material comprising an active substance, a conductive agent, and a binder, wherein the active substance is the nitrogen-doped nanocarbon material described in the first aspect or a nitrogen-doped nanocarbon material prepared according to the preparation method described in the second aspect.

[0060] In some embodiments of the present invention, the content and type of the conductive agent are well known to those skilled in the art, and the conductive agent may be selected from one or more of acetylene black, Ketjen black, graphene, and carbon nanotubes. The present invention preferably uses acetylene black as the conductive agent.

[0061] In some embodiments of the present invention, the adhesive is a binder, which can be any adhesive known in the art that can be used for capacitors. It can be selected from fluorinated resins and / or polyolefin compounds, such as one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber latex, and acrylonitrile copolymer aqueous dispersions, preferably polytetrafluoroethylene (PTFE).

[0062] In some embodiments of the present invention, preferably, the mass ratio of nitrogen-doped carbon nanomaterial, conductive agent and binder is 7-18:1-3:1, for example, it can be 9:0.5:0.5, 8:1:1, 8:1.5:0.5, 7:2:1 and any value within the range formed by any two of these values, preferably 8:1:1.

[0063] A fourth aspect of the present invention provides a capacitor electrode, the electrode comprising a current collector and an electrode material coated and / or filled on the current collector, wherein the electrode material is the electrode material described in the third aspect.

[0064] In some embodiments of the present invention, the current collector can be any type of current collector known to those skilled in the art, such as stainless steel mesh, nickel foam and aluminum foil, with stainless steel mesh being preferred as the current collector.

[0065] Since this invention only relates to the improvement of electrode active materials, there are no particular limitations on other components and structures of the supercapacitor when the nitrogen-doped carbon nanomaterials of this invention are applied to supercapacitors.

[0066] The fifth aspect of the present invention provides a method for preparing a capacitor electrode, the method comprising coating and / or filling a slurry containing an active material, a conductive agent, a binder, and a solvent onto a current collector, drying, and rolling or not rolling, wherein the active material is the nitrogen-doped nano-carbon material described in the first aspect or the nitrogen-doped nano-carbon material prepared according to the preparation method described in the second aspect.

[0067] In some embodiments of the present invention, the solvent may be any solvent known in the art that can be used for the preparation of supercapacitor electrodes, such as anhydrous ethanol and / or N-methylpyrrolidone, preferably anhydrous ethanol. The amount of solvent used is determined by the ability to form the desired coating slurry.

[0068] According to a preferred embodiment of the present invention, the method for preparing the capacitor electrode includes:

[0069] Nitrogen-doped carbon nanomaterials, conductive agents, and binders are mixed, ground evenly, and then mixed with a solvent to form a slurry. The slurry is then evenly coated onto a current collector, dried, and cut into electrode sheets.

[0070] The sixth aspect of the present invention provides a supercapacitor comprising an electrode core and an electrolyte, wherein the electrode core and the electrolyte are sealed within a battery casing, the electrode core comprising an electrode and a separator, and the electrode being either the capacitor electrode described in the fourth aspect or a capacitor electrode prepared according to the preparation method described in the fifth aspect.

[0071] In some embodiments of the present invention, preferably, the supercapacitor is an electric double-layer supercapacitor.

[0072] In some embodiments of the present invention, the electrolyte can be an electrolyte commonly used in the art for supercapacitors, such as an aqueous electrolyte and / or an organic electrolyte, preferably an aqueous electrolyte, and particularly preferably an aqueous alkaline electrolyte, such as a 6 mol / L KOH aqueous solution.

[0073] In some embodiments of the present invention, the separator used in the supercapacitor has electrical insulation and liquid retention properties, is disposed between the electrodes of the electrode core, and is sealed together with the electrode core within the battery casing. The separator can be any type of separator commonly used in the art, such as a composite membrane formed by welding or bonding together various grades of polyethylene, polypropylene, modified polyethylene felt, modified polypropylene felt, ultrafine glass fiber felt, vinylon felt, or nylon felt produced by known manufacturers with wettable polyolefin microporous membranes.

[0074] In some embodiments of the present invention, preferably, the battery casing is a button cell battery casing.

[0075] The nitrogen-doped porous carbon nanomaterials provided by this invention are applied in supercapacitors. When using an aqueous alkaline electrolyte, the single-electrode specific capacitance can reach up to 252 F / g at a current density of 1 A / g, exhibiting excellent capacitance performance.

[0076] The present invention will be described in detail below through embodiments.

[0077] The surface morphology of the material was characterized by high-resolution transmission electron microscopy (HRTEM). The HRTEM used was a JEM-2100 (Nippon Electron Ltd.), and the HRTEM test conditions were: accelerating voltage of 200 kV.

[0078] The pore structure properties of the material were detected using the BET test method. Specifically, a Quantachrome AS-6B analyzer was used for measurement. The specific surface area and pore volume of the material were obtained by the Brunauer-Emmett-Taller (BET) method. The mesopore distribution curve was calculated from the desorption curve using the Barrett-Joyner-Halenda (BJH) method, and the micropore size distribution curve was calculated from the isotherm using the Horvath-Kawazoe (HK) method.

[0079] The content of various elements and nitrogen species on the material surface was determined by X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectroscopy analysis was performed on an ESCALab250 X-ray photoelectron spectrometer from Thermo Scientific equipped with Thermo Avantage V5.926 software. The excitation source was monochromatic Al Kα X-rays with an energy of 1486.6 eV and a power of 150 W. The narrow scan passthrough energy was 30 eV, and the baseline vacuum during analysis was 6.53 × 10⁻⁶. - 9 mbar, electron binding energy was corrected using the C1s peak (284.6 eV) of elemental carbon, and data processing was performed on Thermo Avantage software. Quantitative analysis was conducted using the sensitivity factor method in the analysis module. Before testing, the material was dried in a helium atmosphere at 150°C and 1 standard atmosphere for 3 hours.

[0080] The Raman test uses visible laser Raman spectroscopy, which utilizes a 532 light source to Raman characterize the functional groups of the material and provide characteristic spectra.

[0081] Examples 1-5 illustrate nitrogen-doped carbon nanomaterials and their preparation methods.

[0082] Preparation Example 1

[0083] (1) Precursor preparation: According to the molar ratio of nickel source (calculated as nickel element), nitrogen-containing organic acid and potassium source of 1:1:1, weigh 10g of basic nickel carbonate and 20.08g of ethylenediaminetetraacetic acid and dissolve them in 100mL of deionized water. Stir well to obtain a solution. Then weigh 3.86g of potassium hydroxide and add it to the solution. Heat and stir at 95℃ for 4h. Then place it in an oven to dry and obtain 25g of precursor material. Grind the precursor material into powder for later use.

[0084] (2) Calcination: Weigh 10g of precursor material into a ceramic boat, then place it in a tube furnace. Under nitrogen protection, heat the material to 600℃ at a heating rate of 5℃ / min, calcine at a constant temperature for 4h, and finally cool it to room temperature at a cooling rate of 5℃ / min to obtain 3.0g of pyrolysis product.

[0085] (3) Dissolve 3.0g of pyrolysis product in 50mL of deionized water, stir evenly, add 10mL of 37% concentrated hydrochloric acid, then heat to 100℃, stir for 12h, cool to room temperature, filter, wash with water until neutral, put the obtained product into an oven and dry overnight to obtain 800mg of nitrogen-doped carbon nanomaterials.

[0086] The transmission electron microscope image of the nitrogen-doped carbon nanomaterial is shown below. Figure 1 As shown, from Figure 1 It can be seen that the nano-carbon material has a sheet-like morphology;

[0087] The N2 adsorption-desorption isotherm of the nitrogen-doped carbon nanomaterial is as follows: Figure 2 As shown, the BET specific surface area of ​​this carbon nanomaterial was calculated to be 1529.2 m² using isothermal adsorption-desorption curves. 2 / g, with a specific surface area of ​​1406.3m² within the micropores. 2 / g, accounting for 90% of the total specific surface area; the total pore volume of this nano-carbon material is 0.91cm³. 3 / g, micropore volume is 0.64cm³ 3 / g, accounting for 70% of the total pore volume; the above data indicates that the nano-carbon material is mainly composed of microporous structure;

[0088] The X-ray photoelectron spectroscopy (XPS) of this nitrogen-doped carbon nanomaterial is as follows: Figure 3 As shown in the figure, XPS peaks for C, N, and O are clearly visible. Characteristic peaks for nitrogen are present at 397.5±1 eV, 399.5±eV, and 401.5 eV, while characteristic peaks for oxygen are present at 531-533 eV, further confirming the effective doping of N and the presence of oxygen in the material. The atomic percentages of each element on the surface of this carbon nanomaterial can be calculated based on the peak areas: carbon accounts for 84.91% by mass, oxygen for 9.53% by mass, and nitrogen for 5.56% by mass.

[0089] The high-resolution N1s NPS spectrum of this carbon nanomaterial is shown below. Figure 4 As shown in the figure, the nitrogen in this nano-carbon material consists of pyridine nitrogen, pyrrole nitrogen, and graphitized nitrogen.

[0090] The Raman test results of the nitrogen-doped carbon nanomaterial are as follows: Figure 5 As shown in the figure, the nano-carbon material exhibits distinct D and G peaks, and I... D / I G =1.02, indicating that the nano-carbon material has a certain degree of graphitization.

[0091] The cyclic voltammetry curves of the nitrogen-doped carbon nanomaterial at different scan rates are as follows: Figure 6 As shown in the figure, the curve is elliptical and has redox peaks, indicating that the doping of nitrogen atoms introduces pseudocapacitance, thereby improving the overall performance of the material.

[0092] Preparation Example 2

[0093] Nitrogen-doped carbon nanomaterials were prepared according to the method of Preparation Example 1, except that in step (2), the temperature was increased to 650°C at a heating rate of 5°C / min, and 700 mg of nitrogen-doped carbon nanomaterials were finally obtained.

[0094] Transmission electron microscopy revealed that the nitrogen-doped carbon nanomaterial has a sheet-like morphology.

[0095] The BET specific surface area of ​​this nitrogen-doped carbon nanomaterial was determined to be 1547.5 m² using the BET test method and calculated from the isothermal adsorption-desorption curve. 2 / g, with a specific surface area of ​​1459.8m² within the micropores. 2 / g, accounting for 94% of the total specific surface area; the total pore volume of this nano-carbon material is 0.78cm³. 3 / g, micropore volume is 0.66cm³ 3 / g, accounting for 84.6% of the total pore volume; the above data indicates that the nano-carbon material is mainly composed of microporous structure;

[0096] X-ray photoelectron spectroscopy revealed that the carbon content on the surface of this nitrogen-doped carbon nanomaterial was 86.33%, the oxygen content was 10.01%, and the nitrogen content was 3.66%. The nitrogen in this carbon nanomaterial consisted of pyridine nitrogen, pyrrole nitrogen, and graphitized nitrogen.

[0097] Raman spectroscopy revealed that this nitrogen-doped carbon nanomaterial exhibited distinct D and G peaks, I D / I G =0.98, indicating that the nano-carbon material has a certain degree of graphitization.

[0098] Preparation Example 3

[0099] Nitrogen-doped carbon nanomaterials were prepared according to the method of Preparation Example 1, except that in step (2), the temperature was increased to 700°C at a heating rate of 5°C / min, and 600 mg of nitrogen-doped carbon nanomaterials were finally obtained.

[0100] Transmission electron microscopy revealed that the nitrogen-doped carbon nanomaterial has a sheet-like morphology.

[0101] The BET specific surface area of ​​this nitrogen-doped carbon nanomaterial was determined to be 1541.8 m² using the BET test method and calculated from the isothermal adsorption-desorption curve. 2 / g, with a specific surface area of ​​1451.8m² within the micropores. 2 / g, accounting for 94% of the total specific surface area; the total pore volume of this nano-carbon material is 0.79cm³. 3 / g, micropore volume is 0.66cm³ 3 / g, accounting for 83% of the total pore volume; the above data indicates that the nano-carbon material is mainly composed of microporous structure;

[0102] X-ray photoelectron spectroscopy revealed that the carbon content on the surface of this nitrogen-doped carbon nanomaterial was 88.51%, the oxygen content was 8.64%, and the nitrogen content was 2.85%. The nitrogen in this carbon nanomaterial consisted of pyridine nitrogen, pyrrole nitrogen, and graphitized nitrogen.

[0103] Raman spectroscopy revealed that this nitrogen-doped carbon nanomaterial exhibited distinct D and G peaks, I D / I G =1.01, indicating that the nano-carbon material has a certain degree of graphitization.

[0104] Preparation Example 4

[0105] Nitrogen-doped carbon nanomaterials were prepared according to the method of Preparation Example 1, except that in step (2), the temperature was increased to 600°C at a heating rate of 10°C / min, and 680 mg of nitrogen-doped carbon nanomaterials were finally obtained.

[0106] Transmission electron microscopy revealed that the nitrogen-doped carbon nanomaterial has a sheet-like morphology.

[0107] The BET specific surface area of ​​this nitrogen-doped carbon nanomaterial was determined to be 1480.5 m² using the BET test method and calculated from the isothermal adsorption-desorption curve. 2 / g, with a specific surface area of ​​1295.3m² within the micropores. 2 / g, accounting for 87% of the total specific surface area; the total pore volume of this nano-carbon material is 0.85cm³. 3 / g, micropore volume is 0.71cm³ 3 / g, accounting for 83.5% of the total pore volume; the above data indicates that the nano-carbon material is mainly composed of microporous structure;

[0108] X-ray photoelectron spectroscopy revealed that the carbon content on the surface of this nitrogen-doped carbon nanomaterial was 90.51%, the oxygen content was 7.25%, and the nitrogen content was 2.24%. The nitrogen in this carbon nanomaterial consisted of pyridine nitrogen, pyrrole nitrogen, and graphitized nitrogen.

[0109] Raman spectroscopy revealed that this nitrogen-doped carbon nanomaterial exhibited distinct D and G peaks, I D / I G=0.97, indicating that the nano-carbon material has a certain degree of graphitization.

[0110] Preparation Example 5

[0111] Nitrogen-doped carbon nanomaterials were prepared according to the method of Preparation Example 1, except that in step (1), the amount of potassium hydroxide used was 7.72 g (i.e., the molar ratio of nickel source (calculated as nickel element), nitrogen-containing organic acid and potassium source was 1:1:2), and finally 700 mg of nitrogen-doped carbon nanomaterials were obtained.

[0112] Transmission electron microscopy revealed that the nitrogen-doped carbon nanomaterial has a sheet-like morphology.

[0113] The BET specific surface area of ​​this nitrogen-doped carbon nanomaterial was determined to be 1386.2 m² using the BET test method and calculated from the isothermal adsorption-desorption curve. 2 / g, with a specific surface area of ​​1051.8m² within the micropores. 2 / g, accounting for 75.8% of the total specific surface area; the total pore volume of this nano-carbon material is 0.92cm³. 3 / g, micropore volume is 0.65cm³ 3 / g, accounting for 70.6% of the total pore volume; the above data indicates that the nano-carbon material is mainly composed of microporous structure;

[0114] X-ray photoelectron spectroscopy revealed that the carbon content on the surface of this nitrogen-doped carbon nanomaterial was 85.32%, the oxygen content was 9.57%, and the nitrogen content was 5.11%. The nitrogen in this carbon nanomaterial consisted of pyridine nitrogen, pyrrole nitrogen, and graphitized nitrogen.

[0115] Raman spectroscopy revealed that this nitrogen-doped carbon nanomaterial exhibited distinct D and G peaks, I D / I G =1.02, indicating that the nano-carbon material has a certain degree of graphitization.

[0116] Comparative Preparation Example 1

[0117] Nanocarbon materials were prepared according to the method of Preparation Example 1, except that in the precursor preparation process of step (1), ethylenediaminetetraacetic acid was replaced with citric acid.

[0118] (1) Preparation of precursor: 10g basic nickel carbonate, 30g citric acid and 3.6g potassium hydroxide were dissolved in 100ml deionized water, heated and stirred at 95℃ for 4h and then placed in an oven to dry to obtain 40g precursor material.

[0119] (2) Calcination: The dried precursor material was ground into powder, and 10g was placed in a tube furnace. Under nitrogen protection, the temperature was increased to 600℃ at a heating rate of 5℃ / min, and calcined at a constant temperature for 2h. Finally, it was naturally cooled to room temperature to obtain 4g of black primary product.

[0120] (3) Acid washing: The initial product was dissolved in an appropriate amount of deionized water, stirred evenly, and then an excess of 37% concentrated hydrochloric acid was added. The temperature was then raised to 95°C and stirred for 12 hours. After cooling to room temperature, the mixture was filtered and washed with water until neutral. It was then placed in an oven and dried overnight to finally obtain 950 mg of undoped nano-carbon material.

[0121] The BET specific surface area of ​​this carbon material was calculated to be 364.96 m² using isothermal adsorption-desorption curves. 2 / g, with a microporous internal surface area of ​​58.28m². 2 / g indicates that the material is predominantly mesoporous. The atomic proportions of each element on the material surface can be calculated from the peak areas in X-ray photoelectron spectroscopy (XPS): C is 93.42% and O is 6.58%. The Raman spectroscopy results for this material show that I... D / I G =1.00.

[0122] Comparative Preparation Example 2

[0123] Nanocarbon materials were prepared according to the method of Preparation Example 1, except that potassium hydroxide was not used in the precursor preparation process of step (1).

[0124] (1) Precursor preparation: Accurately weigh 10g of basic nickel carbonate and 20.08g of ethylenediaminetetraacetic acid, dissolve them in 100ml of deionized water, and stir until homogeneous. Heat and stir at 95℃ for 4h, then place in an oven. Finally, 25g of precursor material is obtained, which is ground into powder and set aside for later use.

[0125] (2) Calcination: Accurately weigh 10g of precursor into a ceramic boat, then place it in a tube furnace. Under nitrogen protection, heat the furnace to 600℃ at a heating rate of 5℃ / min, calcine at a constant temperature for 4h, and finally cool it to room temperature at a rate of 5℃ / min to obtain 3.0g of blackish-gray pyrolysis product.

[0126] (3) Dissolve the pyrolysis product in an appropriate amount of deionized water, stir well, and then add 10 ml of 37% hydrochloric acid. The temperature is then raised to 100°C and stirred for 12 hours. After cooling to room temperature, filter, wash with water until neutral, and then place in an oven to dry overnight. 800 mg of nitrogen-doped carbon nanomaterials are obtained.

[0127] The BET specific surface area of ​​this nitrogen-doped carbon nanomaterial was determined to be 328.5 m² using the BET test method and calculated from the isothermal adsorption-desorption curve. 2 / g, with a specific surface area of ​​30.7m² within the micropores. 2 / g, accounting for 10% of the total specific surface area; the total pore volume of this nano-carbon material is 1.45cm³. 3 / g, micropore volume is 0.05cm³ 3 / g, accounting for 3.4% of the total pore volume. X-ray photoelectron spectroscopy determined that the surface of this nitrogen-doped carbon nanomaterial contained 84.91% carbon, 9.53% oxygen, and 5.56% nitrogen by mass. Raman spectroscopy results for this material, I D / I G =0.85.

[0128] Examples 1-5 illustrate capacitor electrode materials, capacitor electrodes, and their preparation methods.

[0129] Example 1

[0130] Preparation of capacitor electrode: Weigh 32 mg of nitrogen-doped carbon nanomaterial prepared in Example 1, mix the carbon nanomaterial, conductive agent (acetylene black) and binder (polytetrafluoroethylene) in a mass ratio of 8:1:1, add an appropriate amount of solvent (anhydrous ethanol) and grind thoroughly, then scrape the slurry onto a clean stainless steel mesh current collector, and then place it in a vacuum oven at 80°C to dry overnight; after drying, cut it into circular electrode sheets with a diameter of 10 mm and a mass of 2 mg, and the active material content on the electrode sheet is 1.6 mg.

[0131] Example 2

[0132] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterials prepared in Preparation Example 2 was used as the active material.

[0133] Example 3

[0134] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterials prepared in Preparation Example 3 was used as the active material.

[0135] Example 4

[0136] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterials prepared in Preparation Example 4 was used as the active material.

[0137] Example 5

[0138] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterials prepared in Preparation Example 5 was used as the active material.

[0139] Comparative Example 1

[0140] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterial prepared in Comparative Preparation Example 1 was weighed as the active material.

[0141] Comparative Example 2

[0142] Preparation of capacitor electrode: The capacitor electrode was prepared according to the method of Example 1, except that the same weight of nitrogen-doped carbon nanomaterial prepared in Comparative Preparation Example 2 was weighed as the active material.

[0143] The test examples are used to test the capacitance performance of capacitor electrodes.

[0144] Test case

[0145] Assembly of the three-electrode testing system: The capacitor electrodes prepared in Examples 1-5 and Comparative Examples 1-2 were used as working electrodes, platinum electrodes as counter electrodes, mercuric oxide electrodes as reference electrodes, and 6 mol / L KOH aqueous solution as electrolyte to assemble the three-electrode testing system.

[0146] Performance testing: The assembled three-electrode test system was subjected to constant current charge-discharge tests. The test voltage range (relative to the mercury oxide electrode) was -1V to 0V, and the specific capacitance was recorded at different current densities (1-10A / g).

[0147] Figure 7 The figures show the constant current charge-discharge curves of the capacitor electrode prepared using the nitrogen-doped carbon nanomaterial from Preparation Example 1 in an aqueous alkaline electrolyte at different current densities. As can be seen from the figures, using a 6 mol / L potassium hydroxide aqueous solution as the electrolyte, the positive electrode of the capacitor prepared in Example 1 has a specific capacitance of 252 F / g at a current density of 1 A / g.

[0148] The specific capacitance of the capacitor electrode prepared in Example 2 is 232 F / g at a current density of 1 A / g.

[0149] The specific capacitance of the capacitor electrode prepared in Example 3 is 202 F / g at a current density of 1 A / g.

[0150] The specific capacitance of the capacitor electrode prepared in Example 4 is 198 F / g at a current density of 1 A / g.

[0151] The specific capacitance of the capacitor electrode prepared in Example 5 is 216 F / g at a current density of 1 A / g.

[0152] The specific capacitance of the capacitor electrode prepared in Comparative Example 1 is 120 F / g at a current density of 1 A / g.

[0153] The specific capacitance of the capacitor electrode prepared in Comparative Example 2 is 130 F / g at a current density of 1 A / g.

[0154] The data analysis above shows that when the nitrogen-doped carbon nanomaterial of the present invention is used as the electrode of the double-layer supercapacitor and an aqueous alkaline electrolyte is used, the single electrode specific capacitance can reach up to 252 F / g at a current density of 1 A / g, exhibiting excellent capacitance performance.

[0155] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A nitrogen-doped porous carbon nanomaterial, characterized in that, The nano-carbon material possesses both microporous and mesoporous structures, and its BET specific surface area is 300-3000 m². 2 / g, the proportion of the specific surface area within the micropores to the total specific surface area is higher than 60%; the total pore volume of the nano-carbon material is 0.7-1.5cm³. 3 / g, the proportion of micropore volume to total pore volume is higher than 60%; the mass percentage of carbon on the surface of the nano-carbon material is 70-95% and the mass percentage of nitrogen is 3.66-20% as determined by X-ray photoelectron spectroscopy; the nano-carbon material has a sheet-like morphology; The preparation method of the nitrogen-doped porous carbon nanomaterial includes the following steps: (1) Precursor preparation: a nickel source, a nitrogen-containing organic acid and a potassium source are mixed with a solvent to form a homogeneous solution, and then the solvent in the homogeneous solution is removed to obtain the precursor material, wherein the nitrogen-containing organic acid is ethylenediaminetetraacetic acid and / or 2,5-pyridinedicarboxylic acid, and the potassium source is selected from one or more of potassium carbonate, potassium bicarbonate and potassium hydroxide; (2) Calcination: Under an inert atmosphere, the precursor material obtained in step (1) is calcined to obtain pyrolysis products; (3) Acid washing: Provide an aqueous solution containing the pyrolysis product obtained in step (2) and react it with acid, then separate the solid and liquid, wash and dry; In step (1), the molar ratio of the nickel source, nitrogen-containing organic acid and potassium source, calculated as nickel element, is 1:1-10:0.1-10; In step (2), the calcination method includes: heating to 400-650℃ at a heating rate of 2-5℃ / min, calcining at a constant temperature for 1-8h, and then cooling to room temperature at a cooling rate of 1-10℃ / min.

2. The nanocarbon material according to claim 1, wherein, The BET specific surface area of ​​the nano-carbon material is 1000-2000 m². 2 / g, the specific surface area inside the micropores accounts for more than 75% of the total specific surface area; the mass percentage of carbon on the surface of the nano-carbon material is 80-95% and the mass percentage of nitrogen is 3.66-15%, as determined by X-ray photoelectron spectroscopy.

3. The nanocarbon material according to claim 1 or 2, wherein, The nano-carbon material has a porous, sheet-like structure.

4. The nanocarbon material according to claim 1 or 2, wherein, In the Raman curve of the nano-carbon material, the intensity ratio of the D peak to the G peak is 0.5-1.

5.

5. The nanocarbon material according to claim 4, wherein, In the Raman curve of the nano-carbon material, the intensity ratio of the D peak to the G peak is 0.7-1.

1.

6. A method for preparing nitrogen-doped carbon nanomaterials according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) Precursor preparation: A homogeneous solution is formed by a nickel source, a nitrogen-containing organic acid and a potassium source with a solvent, and then the solvent in the homogeneous solution is removed to obtain a precursor material. The nitrogen-containing organic acid is ethylenediaminetetraacetic acid and / or 2,5-pyridinedicarboxylic acid, and the potassium source is selected from one or more of potassium carbonate, potassium bicarbonate and potassium hydroxide. (2) Calcination: Under an inert atmosphere, the precursor material obtained in step (1) is calcined to obtain pyrolysis products; (3) Acid washing: Provide an aqueous solution containing the pyrolysis product obtained in step (2) and react it with acid, then separate the solid and liquid, wash and dry; In step (1), the molar ratio of the nickel source, nitrogen-containing organic acid and potassium source, calculated as nickel element, is 1:1-10:0.1-10; In step (2), the calcination method includes: heating to 400-650℃ at a heating rate of 2-5℃ / min, calcining at a constant temperature for 1-8h, and then cooling to room temperature at a cooling rate of 1-10℃ / min.

7. The preparation method according to claim 6, wherein, In step (1), the nickel source is selected from one or more of basic nickel carbonate, nickel acetate, nickel chloride and nickel nitrate; the nitrogen-containing organic acid is ethylenediaminetetraacetic acid; and the potassium source is potassium hydroxide.

8. The preparation method according to claim 7, wherein, In step (1), the nickel source is basic nickel carbonate.

9. The preparation method according to claim 6, wherein, In step (1), the molar ratio of the nickel source, nitrogen-containing organic acid and potassium source, calculated as nickel element, is 1:1-5:0.5-2.

10. The preparation method according to claim 6, wherein, The inert atmosphere is a nitrogen atmosphere and / or an argon atmosphere.

11. The preparation method according to claim 10, wherein, In step (2), the roasting method includes: constant temperature roasting for 2-4 hours, and then cooling down to room temperature at a rate of 3-5℃ / min.

12. The preparation method according to claim 6, wherein, In step (3), the acid used for pickling is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and acetic acid.

13. The preparation method according to claim 12, wherein, In step (3), the acid used for pickling is concentrated hydrochloric acid.

14. The preparation method according to claim 6, wherein, In step (3), the pickling temperature is 80-120℃; the contact reaction time is 6-24h.

15. The preparation method according to claim 14, wherein, In step (3), the pickling temperature is 90-100℃; the contact reaction time is 8-12h.

16. A capacitor electrode material, the electrode material comprising an active substance, a conductive agent, and a binder, characterized in that, The active material is the nitrogen-doped carbon nanomaterial according to any one of claims 1-5 or the nitrogen-doped carbon nanomaterial prepared according to the preparation method according to any one of claims 6-15.

17. The electrode material according to claim 16, wherein, The mass ratio of nitrogen-doped carbon nanomaterials, conductive agents, and binders is 7-18:1-3:

1.

18. A capacitor electrode, comprising a current collector and an electrode material coated and / or filled on the current collector, characterized in that, The electrode material is the electrode material described in claim 16 or 17.

19. The capacitor electrode according to claim 18, wherein, The current collector is selected from one of stainless steel mesh, nickel foam, and aluminum foil.

20. The capacitor electrode according to claim 19, wherein, The current collector is a stainless steel mesh.

21. A method for preparing a capacitor electrode, the method comprising coating and / or filling a slurry containing an active material, a conductive agent, a binder, and a solvent onto a current collector, drying, and calendering or not calendering, characterized in that, The active material is the nitrogen-doped carbon nanomaterial according to any one of claims 1-5 or the nitrogen-doped carbon nanomaterial prepared according to the preparation method according to any one of claims 6-15.

22. The method for preparing capacitor electrodes according to claim 21, wherein, The solvent is anhydrous ethanol and / or N-methylpyrrolidone; And / or, the conductive agent is selected from one or more of acetylene black, Ketjen black, graphene and carbon nanotubes; And / or, the adhesive is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber latex, and acrylonitrile copolymer aqueous dispersion.

23. The method for preparing capacitor electrodes according to claim 22, wherein, The solvent is anhydrous ethanol; And / or, the conductive agent is acetylene black; And / or, the adhesive is polytetrafluoroethylene.

24. A supercapacitor comprising an electrode core and an electrolyte, wherein the electrode core and the electrolyte are sealed within a battery casing, the electrode core comprising electrodes and a separator, characterized in that, The electrode is the capacitor electrode of claim 18 or a capacitor electrode prepared according to the preparation method of any one of claims 21-23.

25. The supercapacitor according to claim 24, wherein, The battery casing is a button cell battery casing.

26. The supercapacitor according to claim 24, wherein, The electrolyte is an aqueous electrolyte or an organic electrolyte.

27. The supercapacitor according to any one of claims 24-26, wherein, The supercapacitor is a double-layer supercapacitor.

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