Low resistivity nitrogen-doped carbon material, method for preparing same, and fuel cell catalyst and lithium ion battery electrode material

Abstract

The application relates to the field of nanometer carbon materials, and discloses a low-resistivity nitrogen-doped carbon material, a preparation method of the low-resistivity nitrogen-doped carbon material, a fuel cell catalyst and a lithium ion battery electrode material. The carbon material is a hollow cage, the molar content of carbon in the carbon material is 89-98% as measured by X-ray photoelectron spectroscopy, the molar content of nitrogen is 0.5-5%, and the molar content of oxygen is 0.5-10%; the carbon material has at least one mesopore distribution peak, the resistivity of the carbon material is not higher than 500 m omega*cm, and the specific surface area of the carbon material is 50-1000 m 2 / g. The low-resistivity nitrogen-doped carbon material has a large specific surface area, increases active sites, has low resistivity, good conductivity, good catalytic performance when applied to a fuel cell catalyst, and good reversible capacity and cycle stability when applied to a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanocarbon materials, in particular to a low-resistivity nitrogen-doped carbon material, a preparation method thereof, a fuel cell catalyst and a lithium ion battery electrode material. BACKGROUND

[0002] Graphene is a two-dimensional carbon nanomaterial with a honeycomb lattice structure composed of carbon atoms in sp 2 hybridized orbitals, which has excellent optical, electrical and mechanical properties and has important application prospects in material science, micro-nano processing, energy, biomedicine and drug delivery, and is considered to be a revolutionary material in the future. However, because graphene is a two-dimensional material, the graphene layers are prone to agglomeration, which limits its application in the macroscopic world. Therefore, more novel nano-graphite carbon materials with new structures have been developed, such as graphite carbon nanocups, nanohorns, nanorings, nanocages and the like. The emergence of these materials enriches the structure of nano-graphite carbon materials and opens up a wider space for their application.

[0003] Among them, graphene nanocage is a very unique new nano-graphite structure, which has a unique hollow structure similar to fullerene and a relatively controllable nanosize. This unique hollow porous nano-graphite structure can endow the material with a series of unique physical and chemical properties, and is expected to be applied in industrial catalysis, electrochemical energy storage, drug carriers, optical devices and many other fields.

[0004] Generally, the preparation methods of graphene nanocarbon cages mainly include laser sputtering method, arc discharge method, supercritical fluid method, chemical vapor deposition method and the like. These methods mostly need to use pre-synthesized metallic particles as a template, use expensive carbon-containing gas (such as methane, acetylene, etc.) as a carbon source, and use high-purity inert gas (such as nitrogen, argon, etc.) as a protective gas. Due to the limitations of technology, the equipment used in these methods has a complex structure and is expensive, the operation is cumbersome and energy-consuming, and the graphene prepared by these methods has irregular morphology, it is difficult to effectively control the morphology and the size is large; the prepared material has many defects, high resistivity and poor electrical conductivity. SUMMARY

[0005] In order to overcome the above-mentioned defects existing in the prior art, the present application provides a low-resistivity nitrogen-doped carbon material, a preparation method thereof, a fuel cell catalyst and a lithium ion battery electrode material. The nitrogen-doped carbon material provided by the present application has a large specific surface area, many active sites, low resistivity and good electrical conductivity, and the preparation method is simple.

[0006] In order to achieve the above object, the first aspect of the present application provides a low-resistivity nitrogen-doped carbon material, the carbon material being a hollow cage, the molar content of carbon of the carbon material being 89-98% as measured by X-ray photoelectron spectroscopy, the molar content of nitrogen being 0.5-5%, and the molar content of oxygen being 0.5-10%; the carbon material having at least one mesopore distribution peak, the resistivity of the carbon material being not higher than 500 mΩ·cm, and the specific surface area of the carbon material being 50-1000 m 2 / g.

[0007] The second aspect of the present application provides a preparation method of a low-resistivity nitrogen-doped carbon material, the method comprising the following steps:

[0008] (1) providing a solution containing a transition metal salt, a polybasic organic carboxylic acid, and a nitrogen-containing compound, and then drying to obtain a precursor material;

[0009] (2) subjecting the precursor material obtained in step (1) to high-temperature pyrolysis under an inert atmosphere or a reducing atmosphere, the temperature of the high-temperature pyrolysis being 800-1300℃, to obtain a pyrolysis product;

[0010] (3) subjecting the pyrolysis product to acid pickling, and then subjecting to solid-liquid separation, washing, and drying.

[0011] The third aspect of the present application provides a fuel cell catalyst, the catalyst containing a carrier and metal Pt supported on the carrier, the carrier being the nitrogen-doped carbon material according to the first aspect or being the nitrogen-doped carbon material prepared according to the method of the second aspect.

[0012] The fourth aspect of the present application provides a lithium ion battery electrode material, the electrode material containing the nitrogen-doped carbon material according to the first aspect or containing the nitrogen-doped carbon material prepared according to the method of the second aspect.

[0013] The method provided by the present application has the following advantages:

[0014] (1) The low-resistivity nitrogen-doped carbon material provided by the present application has a large specific surface area, increases active sites, and has a low resistivity, the resistivity being not higher than 500 mΩ·cm, and has good conductivity, and when applied to a fuel cell catalyst, has good catalytic performance; when applied to a lithium ion battery, shows good reversible capacity and cycle stability.

[0015] (2) The method provided by the application is simple and efficient, the precursor material is directly obtained by mixing a transition metal salt, a polybasic organic carboxylic acid and a nitrogen-containing compound, the atomic utilization rate of the transition metal can reach 100%, and the method overcomes the defects of the prior art, such as the need to use a high-temperature and high-pressure reaction kettle for self-assembly, the waste of a large amount of organic solvents, and the complicated purification steps. In addition, the method provided by the application does not need a polymer additive, and the reaction steps are simplified. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a TEM image of the nitrogen-doped carbon material provided in Example 1;

[0017] Figure 2 is an XRD image of the nitrogen-doped carbon material provided in Example 1;

[0018] Figure 3 is an XPS image of the nitrogen-doped carbon material provided in Example 1;

[0019] Figure 4 is an O1s sub-peak spectrum of the XPS of the nitrogen-doped carbon material provided in Example 1;

[0020] Figure 5 is an N2 adsorption-desorption isotherm of the nitrogen-doped carbon material provided in Example 1;

[0021] Figure 6 is a BJH pore size distribution curve of the nitrogen-doped carbon material provided in Example 1;

[0022] Figure 7 is a Raman spectrum of the nitrogen-doped carbon material provided in Example 1;

[0023] Figure 8 is an O1s sub-peak spectrum of the XPS of the nitrogen-doped carbon material provided in Example 3;

[0024] Figure 9 is a BJH pore size distribution curve of the nitrogen-doped carbon material provided in Example 3;

[0025] Figure 10 is a Raman spectrum of the nitrogen-doped carbon material provided in Example 3;

[0026] Figure 11 is an XRD image of the nitrogen-doped carbon material provided in Example 4;

[0027] Figure 12 is an XPS image of the nitrogen-doped carbon material provided in Example 4;

[0028] Figure 13 is a SEM image of the nitrogen-doped carbon material provided in Example 4, with a magnification of 200K;

[0029] Figure 14 is a TEM image of the nitrogen-doped carbon material provided in Example 4;

[0030] Figure 15 is a XRD image of the nitrogen-doped carbon material provided in Comparative Example 1;

[0031] Figure 16 is an electrochemical performance image of the lithium-ion battery anode material prepared using the nitrogen-doped carbon material of Example 4;

[0032] Figure 17 is an electrochemical performance image of the lithium-ion battery anode material prepared using the nitrogen-doped carbon material of Example 5. DETAILED DESCRIPTION

[0033] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact values and ranges including the endpoints are also encompassed. Various exemplary numerical ranges are stated herein. Whenever a numerical range is stated herein, the range is intended to include all values within the range. Also, individual endpoints of the ranges are also intended to be included. For example, a range of 2.0 to 4.5 is intended to include 2.0, 4.5, and every value and range of values within 2.0 and 4.5, such as 2.0 to 3.5, 2.8 to 4.5, 2.0 to 4.5, 3.5 to 4.5, etc. The same applies to any range or value that is stated herein.

[0034] In the present application, the term "mesopore" is defined as a pore with a pore size in the range of 2-50 nm. Pores with a pore size less than 2 nm are defined as micropores, and pores with a pore size greater than 50 nm are defined as macropores.

[0035] In the present application, the term "mesopore distribution peak" refers to a mesopore distribution peak on a pore distribution curve calculated from a desorption curve according to the Barrett-Joyner-Halenda (BJH) method.

[0036] The first aspect of the present application provides a low-resistivity nitrogen-doped carbon material, the carbon material being a hollow cage, the molar content of carbon in the carbon material being 89-98%, the molar content of nitrogen being 0.5-5%, and the molar content of oxygen being 0.5-10% as measured by X-ray photoelectron spectroscopy; the carbon material having at least one mesopore distribution peak, the resistivity of the carbon material being no higher than 500 mΩ·cm, and the specific surface area of the carbon material being 50-1000 m 2 / g.

[0037] In the present application, the hollow cage has a conventional interpretation in the art, and specifically refers to a hollow sphere or sphere-like shape formed by surrounding layers of graphitized carbon.

[0038] In the present application, the X-ray photoelectron spectroscopy analysis is tested on an ESCA Lab 250 X-ray photoelectron spectrometer of Thermo Scientific Company equipped with Thermo Avantage V5.926 software, the excitation source is monochromatic AlKα X-ray, the energy is 1486.6 eV, the power is 150 W, the penetration energy used for narrow scanning is 30 eV, the base vacuum during the analysis test is 6.53x10 -9 mbar, the electron binding energy is corrected by the C1s peak (284.6 eV) of elemental carbon, the data processing is performed on Thermo Avantage software, and the sensitivity factor method is used in the analysis module for quantitative analysis.

[0039] In the present application, the resistivity of the nitrogen-doped carbon material is measured according to the national standard GB / T 24521-018 Carbon Raw Material and Coke Resistivity Determination Method, and the instrument used is a ST-2722 type semiconductor powder resistivity tester produced by Suzhou Jizhe Electronics Co., Ltd.

[0040] In the present application, the pore structure properties of the carbon material are determined by a Quantachrome AS-6B type analyzer, and the specific surface area and pore volume of the carbon material are obtained by the Brunauer-Emmett-Taller (BET) method.

[0041] According to a preferred embodiment of the present application, the molar content of carbon in the carbon material is 89-97.65%, the molar content of nitrogen is 0.9-5%, and the molar content of oxygen is 1-10%, as measured by X-ray photoelectron spectroscopy.

[0042] Preferably, the carbon material has two or more mesopore distribution peaks.

[0043] Preferably, the carbon material has two mesopore distribution peaks, and the two mesopore distribution peaks correspond to a first most probable pore diameter and a second most probable pore diameter, respectively, the first most probable pore diameter is 3.5-4 nm, and the second most probable pore diameter is 5-20 nm. In this preferred embodiment, the small pore diameter can further provide a large specific surface area for the material, increase the active sites, and the large pore diameter can provide a diffusion channel for molecules or ions, improve the mass transfer efficiency and increase the stability.

[0044] According to a preferred embodiment of the present application, the resistivity of the carbon material is 40-500 mΩ·cm. The carbon material provided by the present application has lower resistivity and better conductivity.

[0045] According to a preferred embodiment of the present application, the specific surface area of the carbon material is 200-1000 m 2 / g.

[0046] According to the present application, preferably, the diameter of the carbon material is 2-200 nm, more preferably 5-50 nm. The diameter of the carbon material is determined by transmission electron microscopy.

[0047] According to the present application, preferably, in the Raman curve of the carbon material, the ratio of I D / I G is 0.2-1.2, more preferably 0.3-1.2. In the Raman curve of the carbon material, I D / I G refers to the ratio of the intensity of D peak and G peak in the Raman curve. The carbon material of the present application has obvious D peak and G peak, and has high degree of graphitization. In the present application, the Raman spectrum is obtained by using RM2000 micro-confocal Raman spectrometer (product of Reinshaw Company), and the technical index is that the excitation source is selected as He-Ne laser with wavelength of 525 nm.

[0048] According to a preferred embodiment of the present application, in the X-ray photoelectron spectrum of the carbon material, the molar ratio of the content of oxygen element determined by the spectrum peak corresponding to C-O group to the content of oxygen element determined by the spectrum peak corresponding to group is 0.01-1.2:1, more preferably 0.1-1:1. In this preferred embodiment, the oxygen species on the surface of the obtained material mainly exists in the form of , and the carbon material has the advantage of being used as an oxidation reaction catalyst.

[0049] According to the present application, the nitrogen-doped carbon material can contain the doping elements applicable to carbon material known to those skilled in the art, and preferably, the nitrogen-doped carbon material does not contain nickel, sulfur, boron, phosphorus, fluorine, chlorine, bromine, iodine and the like.

[0050] The second aspect of the present application provides a preparation method of low-resistivity nitrogen-doped carbon material, which comprises the following steps:

[0051] (1) providing a solution containing transition metal salt, polybasic organic carboxylic acid and nitrogen-containing compound, and then drying to obtain a precursor material;

[0052] (2) pyrolyzing the precursor material obtained in step (1) under inert atmosphere or reducing atmosphere, and the pyrolysis temperature is 800-1300℃, to obtain a pyrolysis product;

[0053] (3) acid washing the pyrolysis product, and then performing solid-liquid separation, washing and drying.

[0054] According to the application, in the preparation method, the precursor material is directly obtained by mixing a transition metal salt, a polybasic organic carboxylic acid and a nitrogen-containing compound, the atomic utilization rate of the transition metal can reach 100%, and the disadvantages of the prior art, such as the need to use a high-temperature and high-pressure reaction kettle for self-assembly, a large amount of organic solvent waste, and a complicated purification process, are overcome. In addition, the preparation method of the application does not require a polymer additive, simplifying the reaction steps, and the low-resistivity nitrogen-doped carbon material prepared has a hollow cage shape, the molar content of carbon in the carbon material is 89-98%, the molar content of nitrogen is 0.5-5%, and the molar content of oxygen is 0.5-10% as measured by X-ray photoelectron spectroscopy; the carbon material has at least one mesopore distribution peak, and the resistivity is not higher than 500 mΩ·cm, and the specific surface area is 50-1000 m 2 / g. The carbon material has a large specific surface area, increasing the active sites, and at the same time has a low resistivity, good conductivity.

[0055] According to the application, in step (1), the formation of the solution is not particularly limited, for example, the solution can be formed by heating, and further preferably by heating and stirring. The application does not particularly limit the temperature of heating and the rate of stirring, and the solution can be formed.

[0056] According to the application, preferably, in step (1), the precursor material is obtained by dissolving a transition metal salt, a polybasic organic carboxylic acid and a nitrogen-containing compound in a solvent to form a solution, and then removing the solvent in the solution. The application does not particularly limit the type of the solvent, and the solution can be formed, preferably, the solvent is water and / or ethanol, and more preferably, the solvent is water; the application also does not particularly limit the amount of the solvent, and the solution can be formed. The solvent in the solution can be removed by drying, and the temperature and process of drying can use the prior art known to those skilled in the art.

[0057] According to the application, preferably, in step (1), the mass ratio of the transition metal salt, the polybasic organic carboxylic acid and the nitrogen-containing compound is 1:0.1-100:0-100, preferably 1:0.5-5:0.1-5, and more preferably 1:0.5-2:0.2-2. The preferred embodiment is more conducive to forming a nitrogen-doped carbon material with a small and uniform size and a hollow cage shape.

[0058] According to the application, preferably, the transition metal is a Group VIII metal, preferably at least one of iron, cobalt, nickel and copper, and more preferably nickel. Preferably, the transition metal salt is one or more of an organic acid salt of the transition metal, a carbonate salt of the transition metal and a basic carbonate salt of the transition metal; and more preferably, the transition metal salt is an organic acid salt of the transition metal.

[0059] According to the present application, preferably, the transition metal salt is selected from at least one of nickel carbonate hydroxide, nickel acetate and cobalt acetate.

[0060] According to the present application, preferably, the polybasic organic carboxylic acid is selected from at least one of citric acid, maleic acid, trimesic acid, terephthalic acid, malic acid, ethylenediaminetetraacetic acid and pyridinedicarboxylic acid, more preferably citric acid and / or ethylenediaminetetraacetic acid.

[0061] According to the present application, preferably, the nitrogen-containing compound is selected from at least one of urea, melamine, dicyandiamide, hexamethylenetetramine and amino acid, more preferably urea and / or hexamethylenetetramine.

[0062] According to a preferred embodiment of the present application, the polybasic organic carboxylic acid and the nitrogen-containing compound can be provided by the same substance, preferably the substance is ethylenediaminetetraacetic acid. Preferably, when the polybasic organic carboxylic acid and the nitrogen-containing compound are provided by the same substance, the mass ratio of the transition metal salt to the substance is 1:0.5-5, preferably 1:0.7-4.

[0063] According to the present application, in step (2), the temperature of the high-temperature pyrolysis is 800-1300℃, preferably the temperature of the high-temperature pyrolysis is 900-1200℃. In the present application, if the temperature of the high-temperature pyrolysis is too low, it is not conducive to the removal of transition metals, in addition, if the temperature is too low, the graphitization degree of the material is low, the resistivity is large and the conductivity is poor, which is not conducive to the formation of a material with low resistivity; and if the temperature of the pyrolysis is too high, the energy consumption is high.

[0064] According to the present application, preferably, in step (2), the process of the high-temperature pyrolysis comprises: heating at a rate of 0.5-30℃ / min, preferably 1-10℃ / min, and further preferably 5-10℃ / min to the temperature of the high-temperature pyrolysis, and keeping constant temperature.

[0065] Preferably, the time of the constant temperature is 20-600min, preferably 60-480min.

[0066] In the present application, the temperature is raised at the rate within the above-mentioned limited range, on the one hand, it is conducive to improving the graphitization degree of the nitrogen-doped carbon material, thereby reducing the resistivity of the carbon material and improving the conductivity; on the other hand, it is also conducive to improving the removal rate of transition metals in the pickling process.

[0067] According to a preferred embodiment of the present application, in step (2), the temperature is raised to the high-temperature pyrolysis temperature in two stages, specifically, the temperature is first raised to 500-800°C, preferably 600-700°C, at a rate of 0.5-30°C / min, preferably 1-10°C / min, and then kept constant for 20-600 min, preferably 60-480 min, and then the temperature is further raised to the high-temperature pyrolysis temperature at a rate of 0.5-30°C / min, preferably 1-10°C / min, and then kept constant for 20-600 min, preferably 60-480 min.

[0068] According to the present application, preferably, the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium; and / or,

[0069] The reducing atmosphere is provided by hydrogen and optionally an inert gas, which is at least one of nitrogen, argon, neon and helium.

[0070] According to the present application, preferably, in step (3), the pyrolysis product is subjected to acid washing with an aqueous inorganic acid solution and / or an aqueous organic acid solution, specifically, the pyrolysis product is mixed with the aqueous inorganic acid solution and / or the aqueous organic acid solution, and the mixing method is not particularly limited in the present application, and the mixing can be performed by ultrasonic or stirring. The acid washing removes transition metal from the pyrolysis product, thereby forming a nitrogen-doped carbon material with a hollow cage structure.

[0071] Preferably, the aqueous inorganic acid solution and / or the aqueous organic acid solution is one or more of an aqueous hydrochloric acid solution, an aqueous sulfuric acid solution, an aqueous nitric acid solution and an aqueous citric acid solution, and is further preferably an aqueous hydrochloric acid solution; preferably, the concentration of the aqueous inorganic acid solution and / or the aqueous organic acid solution is 0.1-10 mol / L; preferably, the pH value of the aqueous inorganic acid solution or the aqueous organic acid solution is less than 7.

[0072] According to the present application, preferably, in step (3), the acid washing is performed at a temperature of 20-120°C, preferably 60-100°C, for a time of 0.1-48 h, preferably 4-12 h.

[0073] According to the present application, in step (3), the solid-liquid separation method is not particularly limited, and any method known in the art can be used, for example, filtration can be used. Since the filtrate contains a large amount of transition metal salts, preferably, the filtrate obtained by the solid-liquid separation can be used as a raw material for preparing a precursor material, specifically, the filtrate is mixed with a nitrogen-containing compound and / or a polybasic organic carboxylic acid to form a solution, and then the solvent in the solution is removed to obtain the precursor material.

[0074] According to the present application, the washing is used to remove the acid remaining on the nitrogen-doped carbon material in the pickling process, and thus, various water washing methods capable of washing the nitrogen-doped carbon material to neutral can be applied to the present application.

[0075] According to the present application, the drying is used to remove the water on the nitrogen-doped carbon material. The drying can be performed by using normal pressure drying or reduced pressure drying. The conditions of the drying can include a temperature of 100-120°C and a time of 6-10h.

[0076] According to the present application, preferably, the transition metal salt, the polybasic organic carboxylic acid, and the nitrogen-containing compound are used in an amount such that the nitrogen-doped carbon material has a carbon molar content of 89-98%, a nitrogen molar content of 0.5-5%, and an oxygen molar content of 0.5-10%.

[0077] According to some embodiments of the present application, more preferably, the transition metal salt, the polybasic organic carboxylic acid, and the nitrogen-containing compound are used in an amount such that the nitrogen-doped carbon material has a carbon molar content of 89-97.65%, a nitrogen molar content of 0.9-5%, and an oxygen molar content of 1-10%.

[0078] According to the present application, the nitrogen-doped carbon material can contain a doping element applicable to carbon materials known to those skilled in the art, and preferably, the nitrogen-doped carbon material does not contain nickel, sulfur, boron, phosphorus, fluorine, chlorine, bromine, iodine, and the like.

[0079] The third aspect of the present application provides a fuel cell catalyst, the catalyst containing a carrier and a metal Pt supported on the carrier, the carrier being the nitrogen-doped carbon material according to the first aspect or the nitrogen-doped carbon material prepared according to the method of the second aspect.

[0080] According to some embodiments of the present application, the fuel cell catalyst can be prepared by using a method for preparing a fuel cell catalyst known in the art, and the present application is not particularly limited thereto. Preferably, the method for preparing the fuel cell catalyst comprises:

[0081] (a) dispersing the nitrogen-doped carbon material in a solvent, and then adding a platinum compound to the solvent in which the nitrogen-doped carbon material is dispersed, to obtain a suspension;

[0082] (b) contacting a reducing agent with the suspension.

[0083] According to some embodiments of the present application, the solvent can be all the solvents known in the art that can be used to prepare a fuel cell catalyst, and preferably, at least one of water, ethanol, and ethylene glycol. Preferably, the solvent is used in an amount of 50-1500mL per 1g of the nitrogen-doped carbon material.

[0084] According to some embodiments of the present invention, the platinum compound may be a platinum compound known in the art for use in preparing fuel cell catalysts, such as at least one of chloroplatinic acid, chloroplatinate, platinum chloride, platinum nitrate, and platinum complexes, preferably chloroplatinic acid. Preferably, the molar ratio of nitrogen-doped carbon material to platinum compound based on elemental platinum is 10-70:1.

[0085] According to some embodiments of the present invention, the reducing agent may be a reducing agent known in the art, such as at least one selected from formaldehyde, formic acid, sodium thiosulfate, sodium borohydride, and potassium borohydride, preferably formic acid. Preferably, the molar ratio of the reducing agent to the platinum compound (based on elemental platinum) is 2-10:1.

[0086] According to some embodiments of the present invention, preferably, the pH of the suspension is 9-11.

[0087] According to some embodiments of the present invention, preferably, the temperature at which the reducing agent contacts the suspension is 30-90°C, and the contact time is 0.1-8 hours. Preferably, after the reducing agent contacts the suspension, the reaction mixture is further filtered, and the resulting filter cake is washed and dried.

[0088] According to some embodiments of the present invention, preferably, the Pt loading in the fuel cell catalyst is 40 wt%, based on the total weight of the fuel cell catalyst.

[0089] The nitrogen-doped carbon material provided by this invention is a hollow cage-like structure with numerous mesoporous components, a large specific surface area, and low resistivity, making it suitable as a support for fuel cell catalysts. Since this invention only relates to improvements in the support, there are no particular limitations on other components and structures of the fuel cell catalyst when using the nitrogen-doped carbon material of this invention in the fuel cell catalyst. When the Pt / C catalyst prepared using the nitrogen-doped carbon material provided by this invention is applied to the oxygen reduction reaction, it exhibits a half-wave potential of 0.85-0.89 V and an electrochemical active area (ECSA) of 50-86 μm. 2 g -1 -Pt, with a specific activity of 0.069-0.160 mg. -1 -Pt, with an area-to-specific activity of 0.1-0.25 mA mg. -1 -Pt exhibits excellent catalytic performance.

[0090] A fourth aspect of the present invention provides a lithium-ion battery electrode material, wherein the electrode material contains the nitrogen-doped carbon material described in the first aspect or contains the nitrogen-doped carbon material prepared according to the method described in the second aspect.

[0091] According to some embodiments of the present invention, preferably, the lithium-ion battery electrode material contains an active material, a conductive agent, and a binder, wherein the active material is the nitrogen-doped carbon material described in the first aspect or the nitrogen-doped carbon material prepared according to the method described in the second aspect.

[0092] According to some embodiments of the present invention, preferably, the mass ratio of active material, conductive agent and binder in the lithium-ion battery electrode material is 7-18:0-3:1, for example, it can be 9:0.5:0.5, 8:1:1, 8:1.5:0.5, 7:1:2, 9:0:1 and any value within the range formed by any two of these values, preferably 8-18:1-3:1, more preferably 8:1:1 or 7:1:2.

[0093] According to some embodiments of the present invention, the content and type of the conductive agent are known to those skilled in the art. Preferably, the conductive agent is selected from at least one of acetylene black, Ketjen black, graphene and carbon nanotubes, and more preferably acetylene black.

[0094] According to some embodiments of the present invention, the binder may be any binder known in the art that can be used in lithium-ion batteries, preferably a fluorinated resin and / or a polyolefin compound. More preferably, the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber latex, and acrylonitrile copolymer aqueous dispersion, and further preferably polyvinylidene fluoride (PVDF).

[0095] According to some embodiments of the present invention, the lithium-ion battery electrode material can be used to prepare a lithium-ion battery electrode. Preferably, the electrode includes a current collector and an electrode material coated and / or filled on the current collector, wherein the electrode material is the lithium-ion battery electrode material described in the fourth aspect.

[0096] According to some embodiments of the present invention, the current collector can be any of the current collectors known to those skilled in the art. Preferably, the current collector is selected from any one of stainless steel mesh, nickel foam, aluminum foil and copper foil, and more preferably copper foil.

[0097] According to some embodiments of the present invention, preferably, the method for preparing the lithium-ion battery electrode includes coating and / or filling a slurry containing a lithium-ion battery electrode material and a solvent onto a current collector, drying, calendering or not calendering, wherein the lithium-ion battery electrode material is the lithium-ion battery electrode material described in the fourth aspect.

[0098] According to some embodiments of the present invention, the type and amount of the solvent are known to those skilled in the art, and all solvents known in the art that can be used for the preparation of lithium-ion battery electrodes can be used. Preferably, the solvent is anhydrous ethanol and / or N-methylpyrrolidone, more preferably N-methylpyrrolidone (NMP); the amount of the solvent is determined by the ability to form the desired coating slurry.

[0099] According to some embodiments of the present invention, the lithium-ion battery includes an electrode core and an electrolyte, the electrode core and the electrolyte being sealed within a battery casing, the electrode core including a positive electrode, a negative electrode and a separator, the negative electrode being a lithium-ion battery electrode as described above.

[0100] According to some embodiments of the present invention, preferably, the battery casing is a button cell battery casing.

[0101] According to some embodiments of the present invention, the electrolyte can be an electrolyte commonly used in the art for lithium-ion batteries. Preferably, the electrolyte is a lithium hexafluorophosphate electrolyte, and more preferably, it is a 1 mol / L LiPF6 solution of ethylene carbonate-dimethyl carbonate-ethyl methyl carbonate (volume ratio 1:1:1).

[0102] According to some embodiments of the present invention, the separator has electrical insulation and liquid retention properties, is disposed between the positive and negative 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; preferably, the separator is selected from any one of polyethylene membrane, polypropylene membrane, and cellulose membrane; more preferably, the separator is a polypropylene membrane.

[0103] According to some embodiments of the present invention, the lithium-ion battery can directly use a lithium metal sheet as the positive electrode.

[0104] The lithium-ion battery electrode made using the lithium-ion battery electrode material provided by this invention has a large number of mesoporous structures and a large specific surface area due to the nitrogen-doped carbon material contained in the electrode material, which is beneficial to the transport of electrolyte ions. At the same time, it has a low resistivity and good conductivity. The electrode made by combining conductive agent and binder exhibits good reversible capacity and cycle stability in lithium-ion batteries.

[0105] The present invention will be described in detail below through embodiments.

[0106] Unless otherwise specified, all reagents used in this invention are of analytical grade and are commercially available.

[0107] XRD was used to obtain information about the composition of carbon materials and the structure or morphology of atoms or molecules inside the carbon materials. The XRD diffractometer used was an XRD-6000 X-ray powder diffractometer (Shimadzu, Japan). The XRD test conditions were: Cu target, Kα rays (wavelength λ = 0.154 nm), tube voltage 40 kV, tube current 200 mA, and scanning speed 10o(2θ) / min.

[0108] The morphology of the carbon material was characterized using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The SEM used was a NovaNano SEM 450, with the following testing conditions: accelerating voltage 20kV-30kV, resolution limit approximately 1.2nm, and magnification 25-200Kx. The HRTEM used was a JEM-2100 (Nippon Electron Ltd.), with an accelerating voltage of 200kV. The diameter of the carbon material was measured using HRTEM.

[0109] The pore structure properties of carbon materials 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 carbon materials were obtained using 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.

[0110] The content of various elements and nitrogen and oxygen species on the surface of carbon materials 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 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. Carbon materials were dried in a helium atmosphere at 150°C and 1 standard atmosphere for 3 hours before testing.

[0111] The resistivity of carbon materials was measured according to the national standard GB / T 24521-018 Method for Determining Resistivity of Carbon Raw Materials and Coke, and the instrument used was the ST-2722 semiconductor powder resistivity tester manufactured by Suzhou Jingge Electronics Co., Ltd.

[0112] The degree of graphitization of carbon materials was characterized by Raman spectroscopy at 1355 cm⁻¹. -1 The peak (D peak) is attributed to structural defects, consisting of amorphous carbon, at 1585 cm⁻¹. -1 The peak (G peak) is attributed to carbon in a planar structure. I0 is typically used. D / I G The intensity ratio of the D peak to the G peak is used to characterize the degree of graphitization of carbon materials. D / I G The higher the value, the more defects and the lower the degree of graphitization. The Raman spectra of carbon materials were obtained using an RM2000 microconfocal Raman spectrometer (Reinshaw product). Technical specifications: The excitation source was a He-Ne laser with a wavelength of 525 nm.

[0113] The electrochemical performance of the Pt / C catalyst was tested according to GB / T 20042.4-2009 Test Method for Electrocatalysts of Proton Exchange Membrane Fuel Cells.

[0114] The charge-discharge performance of button cells is tested using the constant current charge-discharge method. By applying a constant current to the battery and conducting charge-discharge tests, the relationship between potential and time is recorded, the specific capacitance during discharge is calculated, and the charge-discharge performance of the battery is measured.

[0115] The charge and discharge performance of coin cells was tested using the CT2001A Land battery testing system from Wuhan Landian Company. The charge and discharge voltage range was 0.005-3V, and the current density for cycle performance testing was 0.2A / g.

[0116] Examples 1-8 illustrate nitrogen-doped carbon materials and their preparation methods.

[0117] Example 1

[0118] (1) Weigh 20g of basic nickel carbonate, 20g of citric acid and 16.34g of urea, add them to a beaker containing 100mL of deionized water, stir at 80℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0119] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 80 mL / min, and heat it to 850°C at a rate of 10°C / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0120] (3) Add the pyrolysis product obtained in step (2) to an aqueous solution containing 1M hydrochloric acid and stir at 90°C for 4 hours. Then filter, collect the filtrate, wash with deionized water until the filtrate is neutral, and then dry the filter cake in a constant temperature oven at 120°C for 6 hours to obtain nitrogen-doped carbon material.

[0121] Figure 1 The image shows a TEM image of the nitrogen-doped carbon material. It can be seen that many carbon cage units are intertwined in the material, and each unit is a hollow cage with a diameter of about 5-20 nm and obvious graphite carbon lattice stripes.

[0122] The XRD pattern of the nitrogen-doped carbon material is as follows: Figure 2 As shown, the peak appearing at 2θ = 26.3° is a diffraction peak of the (002) plane of carbon. The peak shape is a relatively narrow sharp peak, and the carbon formed on the surface is crystalline carbon with a high degree of graphitization. At the same time, the 001 peak of carbon can also be seen at 2θ = 43.67°.

[0123] The XPS plot of the nitrogen-doped carbon material is as follows: Figure 3 As shown in the figure, in addition to carbon, the nitrogen-doped carbon material also contains oxygen and nitrogen. Based on the peak area, the molar content of carbon in the nitrogen-doped carbon material is calculated to be 90.80%, the molar content of oxygen is 4.87%, and the molar content of nitrogen is 4.33%.

[0124] The O1s peak spectrum of the XPS of this nitrogen-doped carbon material is as follows: Figure 4 As shown, using XPS peak splitting software, the oxygen content determined by the peaks corresponding to the CO group can be calculated, along with the content determined by the peaks corresponding to the CO group. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.8569.

[0125] Figure 5 The N2 adsorption-desorption isotherm for this material is given. BET testing shows that the specific surface area of ​​this material is 685.107 m². 2 / g, pore volume is 1.646cm³ 3 / g;

[0126] Figure 6 The figure shows the BJH pore size distribution curve of the material. As can be seen from the figure, there are two mesopore distribution peaks at 3.8 nm and 8.8 nm.

[0127] Figure 7 From the Raman spectrum of this material, the Ig of the material can be calculated. D / I G The value of 1.1150 indicates that the material has a high degree of graphitization.

[0128] The resistivity of the material was measured to be 321 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0129] Example 2

[0130] (1) Weigh 20g of basic nickel carbonate, 20g of citric acid and 4.09g of urea, add them to a beaker containing 60mL of deionized water, stir at 80℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0131] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 80 mL / min, and heat it to 900℃ at a rate of 10℃ / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0132] (3) Add the pyrolysis product obtained in step (2) to an aqueous solution containing 20g of citric acid and stir at 90°C for 4h. Then filter, collect the filtrate, wash with deionized water until the filtrate is neutral, and then dry the filter cake in a constant temperature oven at 120°C for 6h to obtain nitrogen-doped carbon material.

[0133] XPS analysis revealed that the material contained 96.13% carbon, 2.92% oxygen, and 0.95% nitrogen in molar amounts. Using XPS peak analysis software, the oxygen content determined by the peaks corresponding to the CO group and the content determined by the peaks corresponding to the CO group can be calculated. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.7315.

[0134] TEM tests showed that the material is a hollow cage-like structure with a diameter of approximately 5-20 nm.

[0135] BET testing showed that the specific surface area of ​​this material was 908.72 m². 2 / g, pore volume is 2.77cm³ 3 / g, the BJH pore size distribution curve of this material shows two mesoporous distribution peaks at 3.72nm and 11.2nm.

[0136] The I of this material was determined by Raman spectroscopy. D / I G The value is 0.7504, indicating that the material has a high degree of graphitization.

[0137] The resistivity of the material was measured to be 251 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0138] Example 3

[0139] (1) Weigh 15g of basic nickel carbonate and 14.9g of ethylenediaminetetraacetic acid, add them to a beaker containing 40mL of deionized water, stir and mix them evenly at 80℃, and continue to heat and evaporate to dryness to obtain the precursor material.

[0140] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 80 mL / min, and heat it to 600℃ at a rate of 10℃ / min. After holding the temperature for 1 hour, continue to heat it to 900℃ at a rate of 10℃ / min and hold the temperature for 2 hours. Then stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0141] (3) Add the pyrolysis product obtained in step (2) to an aqueous solution containing 2M hydrochloric acid and stir at 90°C for 8 hours. Then filter, collect the filtrate, wash with deionized water until the filtrate is neutral, and then dry the filter cake in a constant temperature oven at 120°C for 6 hours to obtain nitrogen-doped carbon material.

[0142] XPS analysis revealed that the material contains 95.70% carbon, 2.89% oxygen, and 1.41% nitrogen in molar amounts.

[0143] The O1s peak spectrum of the XPS of this material is as follows: Figure 8 As shown, using XPS peak splitting software, the oxygen content determined by the peaks corresponding to the CO group can be calculated, along with the content determined by the peaks corresponding to the CO group. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.4793.

[0144] TEM tests showed that the material is a hollow cage-like structure with a diameter of approximately 5-20 nm.

[0145] BET testing showed that the specific surface area of ​​this material was 479.11 m². 2 / g, pore volume is 1.26cm³ 3 / g; Figure 9 The figure shows the BJH pore size distribution curve of the material. As can be seen from the figure, there are two mesopore distribution peaks at 3.58 nm and 11.02 nm.

[0146] Figure 10 From the Raman spectrum of this material, the Ig of this material can be calculated. D / I G The value is 0.6167, indicating that the material has a high degree of graphitization.

[0147] The resistivity of the material was measured to be 126 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0148] Example 4

[0149] (1) Weigh 10g of nickel acetate, 20g of citric acid and 10g of hexamethylenetetramine, add them to a beaker containing 100mL of deionized water, stir at 80℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0150] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 150 mL / min, and heat it to 1100℃ at a rate of 5℃ / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0151] (3) Add the pyrolysis product obtained in step (2) to an aqueous solution containing 20g of citric acid and stir at 100℃ for 4h. Then filter, collect the filtrate, wash with deionized water until the filtrate is neutral, and then dry the filter cake in a constant temperature oven at 120℃ for 6h to obtain nitrogen-doped carbon material.

[0152] The XRD pattern of the nitrogen-doped carbon material is as follows: Figure 11 As shown, XRD testing reveals that the carbon in this nitrogen-doped carbon material is graphite-structured carbon, without any other impurity phases.

[0153] The XPS plot of the material is as follows: Figure 12 As shown in the figure, in addition to carbon, the material also contains oxygen and nitrogen. Based on the peak area, the molar content of carbon in the nitrogen-doped carbon material is calculated to be 93.03%, the molar content of oxygen is 5.23%, and the molar content of nitrogen is 1.74%.

[0154] Using XPS peak analysis software, the oxygen content in the material, determined by the peaks corresponding to CO groups, can be calculated, along with the content determined by the peaks corresponding to CO groups. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.6352.

[0155] Figure 13 The image shows a SEM image of the material, which reveals that it is a hollow, spherical structure formed by a layer of graphitized carbon surrounding it.

[0156] Figure 14 The image shows a TEM image of the material. It can be seen that the material consists of many carbon cage units interwoven together, and each unit is a hollow cage with a diameter of about 5-20 nm and obvious graphite carbon lattice stripes.

[0157] BET testing showed that the specific surface area of ​​this material is 272.3 m². 2 / g, pore volume is 0.53cm³ 3 / g, the BJH pore size distribution curve of this material shows two mesoporous distribution peaks at 3.88nm and 19.2nm.

[0158] The I of this material was determined by Raman spectroscopy. D / I G The value is 0.7504, indicating that the material has a high degree of graphitization.

[0159] The resistivity of the material was measured to be 230 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0160] Example 5

[0161] (1) Weigh 10g of nickel acetate, 10g of citric acid and 10g of hexamethylenetetramine, add them to a beaker containing 30mL of deionized water, stir at 70℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0162] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 100 mL / min, and heat it to 1200℃ at a rate of 5℃ / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0163] (3) Add the above pyrolysis product to a 2.0M hydrochloric acid aqueous solution and stir at 80°C for 10 hours. Then filter and wash with deionized water until the filtrate is neutral. Dry the filter cake at 120°C for 4 hours to obtain nitrogen-doped carbon material.

[0164] XPS analysis revealed that the material contains 97.65% carbon, 1.34% oxygen, and 1.01% nitrogen molar content. Using XPS peak analysis software, the oxygen content determined by the peaks corresponding to the CO group and the content determined by the peaks corresponding to the CO group can be calculated. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.5321.

[0165] TEM tests showed that the material is a hollow cage-like structure with a diameter of approximately 5-20 nm.

[0166] BET testing shows that the specific surface area of ​​this material is 327.75 m². 2 / g, pore volume is 0.56cm³ 3 / g, the BJH pore size distribution curve of this material shows two mesoporous distribution peaks at 3.82nm and 16.4nm.

[0167] The I of this material was determined by Raman spectroscopy. D / I GThe value is 0.493, indicating that the material has a high degree of graphitization; the resistivity of the material was measured to be 123 mΩ·cm by a conductivity meter, which is low and indicates good electrical conductivity.

[0168] Example 6

[0169] (1) Weigh 10g cobalt acetate, 10g citric acid and 20g hexamethylenetetramine, add them to a beaker containing 150mL deionized water, stir at 60℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0170] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 100 mL / min, and heat it to 1000℃ at a rate of 5℃ / min. After holding the temperature for 1 hour, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0171] (3) Add the pyrolysis product obtained in step (2) to a 2.0M nitric acid aqueous solution and stir at 120°C for 4 hours. Then filter and wash with deionized water until the filtrate is neutral. Dry the filter cake at 120°C for 4 hours to obtain nitrogen-doped carbon material.

[0172] XPS analysis revealed that the material contained 93.98% carbon, 2.78% oxygen, and 3.24% nitrogen in molar amounts. Using XPS peak analysis software, the oxygen content determined by the peaks corresponding to the CO group and the content determined by the peaks corresponding to the CO group were calculated. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.168.

[0173] TEM tests show that the material consists of many carbon cages interwoven together, each unit being a hollow cage with a diameter of approximately 5-20 nm and exhibiting distinct graphite carbon lattice striations.

[0174] BET testing shows that the specific surface area of ​​this material is 368.23 μm. 2 / g, pore volume is 0.78cm³ 3 / g, the BJH pore size distribution curve of this material shows two mesoporous distribution peaks at 3.75nm and 18.1nm.

[0175] The I of the material was measured by Raman spectroscopy. D / I G The value is 0.583, indicating that the material has a high degree of graphitization.

[0176] The resistivity of the material was measured to be 324 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0177] Example 7

[0178] (1) Weigh 10g of nickel acetate, 5g of citric acid and 20g of hexamethylenetetramine, add them to a beaker containing 150mL of deionized water, stir and react at 60℃ for 24h, and then continue to heat and evaporate to dryness to obtain the precursor material.

[0179] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 100 mL / min, and heat it to 1200℃ at a rate of 4℃ / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0180] (3) Add the pyrolysis product obtained in step (2) to a 2.0M HCl aqueous solution and sonicate at 20°C for 10h. Then filter, collect the filtrate, and wash with deionized water until the filtrate is neutral. Dry the filter cake at 80°C for 12h to obtain nitrogen-doped carbon material.

[0181] XPS analysis revealed that the material contained 94.53% carbon, 1.24% oxygen, and 4.23% nitrogen in molar amounts. Using XPS peak analysis software, the oxygen content determined by the peaks corresponding to the CO group and the content determined by the peaks corresponding to the CO group can be calculated. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.168.

[0182] TEM tests showed that the material is a hollow cage-like structure with a diameter of approximately 5-20 nm.

[0183] BET testing showed that the specific surface area of ​​this material is 413.5 m². 2 / g, pore volume is 0.94cm³ 3 / g, the BJH pore size distribution curve of this material shows two mesoporous distribution peaks at 3.78nm and 15.7nm.

[0184] The I of the material was measured by Raman spectroscopy. D / I G The value of 0.345 indicates that the material has a high degree of graphitization.

[0185] The resistivity of the material was measured to be 457 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0186] Example 8

[0187] (1) Add 10g of hexamethylenetetramine to the filtrate collected in Example 2 and mix well. Then evaporate the water to obtain the precursor material.

[0188] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce argon gas with a flow rate of 50 mL / min, and heat it to 900℃ at a rate of 10℃ / min. After holding the temperature for 1 hour, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0189] (3) The pyrolysis product obtained in step (2) is added to a 1M nitric acid aqueous solution, stirred at 60°C for 8 hours, filtered, washed, and washed with deionized water until the filtrate is neutral. Then the filter cake is dried in a constant temperature oven at 100°C for 4 hours to obtain nitrogen-doped carbon material.

[0190] XPS analysis revealed that the material contains 93.57% carbon, 4.78% oxygen, and 1.65% nitrogen. Using XPS peak analysis software, the oxygen content determined by the peaks corresponding to the CO group and the content determined by the peaks corresponding to the CO group can be calculated. The molar ratio of oxygen content determined by the spectral peaks of the functional group is 0.5978.

[0191] TEM tests showed that the material is a hollow cage-like structure with a diameter of approximately 5-20 nm.

[0192] BET testing showed that the specific surface area of ​​this material is 256.3 m². 2 / g, pore volume is 0.48cm³ 3 / g, its BJH pore size distribution curve has two mesoporous distribution peaks at 3.92nm and 18.1nm.

[0193] The I of the material was measured by Raman spectroscopy. D / I G The value of 0.382 indicates that the material has a high degree of graphitization.

[0194] The resistivity of the material was measured to be 198 mΩ·cm using a conductivity meter. The resistivity is low and the conductivity is good.

[0195] Comparative Example 1

[0196] (1) Weigh 20g of basic nickel carbonate, 20g of citric acid and 16.34g of urea, add them to a beaker containing 100mL of deionized water, stir at 80℃ to obtain a homogeneous solution, and continue to heat to dryness to obtain the precursor material.

[0197] (2) Place the precursor material obtained in step (1) into a ceramic boat, then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas with a flow rate of 80 mL / min, and heat it to 650°C at a rate of 10°C / min. After holding the temperature for 2 hours, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain the pyrolysis product.

[0198] (3) Add the pyrolysis product obtained in step (2) to an aqueous solution containing 1M hydrochloric acid and stir at 90°C for 4 hours. Then filter, collect the filtrate, wash with deionized water until the filtrate is neutral, and then dry the filter cake in a constant temperature oven at 120°C for 6 hours to obtain nitrogen-doped carbon material.

[0199] The XRD pattern of the nitrogen-doped carbon material is as follows: Figure 15 As shown in the figure, in addition to the carbon 002 surface peak at 2θ of 25.8°, the nitrogen-doped carbon material also shows elemental nickel peaks at 2θ of 44.38°, 47.44°, 51.8° and 76.3°, indicating that in addition to carbon, elemental nickel is also present in the carbon material.

[0200] The resistivity of this nitrogen-doped carbon material was measured to be 1328 mΩ·cm using a conductivity meter. The resistivity is relatively high, indicating poor conductivity.

[0201] Test Example 1

[0202] This test example illustrates fuel cell catalysts and their preparation methods.

[0203] Preparation of Pt / C catalysts: 0.6 g of nitrogen-doped carbon nanomaterials obtained in Examples 1-8 were dispersed in 200 mL of deionized water, a certain amount of chloroplatinic acid was added, and the mixture was ultrasonically dispersed to form a suspension. Then, sodium carbonate aqueous solution was added to adjust the pH of the suspension to 11. The suspension was heated to 80 °C, and formic acid was added under stirring to carry out a reduction reaction. The molar ratio of the reducing agent to chloroplatinic acid (calculated as platinum) was 5:1, and the reaction was maintained for 8 h. The mixture after the reaction was filtered, washed until the pH of the solution was neutral, and dried at 100 °C to obtain Pt / C catalysts A1-A8 with a Pt loading of 40% by weight.

[0204] Catalytic performance test of Pt / C catalysts: The prepared Pt / C catalysts A1-A8 were applied to the oxygen reduction reaction (ORR) for catalytic performance test. The corresponding catalytic performance is shown in Table 1.

[0205] Comparative Test Example 1

[0206] Preparation of Pt / C catalyst: 0.6 g of carbon material obtained in Comparative Example 1 was dispersed in 200 mL of deionized water, a certain amount of chloroplatinic acid was added, and the mixture was ultrasonically dispersed to form a suspension. Then, sodium carbonate aqueous solution was added to adjust the pH of the suspension to 11. The suspension was heated to 80 °C, and formic acid was added under stirring to carry out a reduction reaction. The molar ratio of the reducing agent to chloroplatinic acid (calculated as platinum) was 5:1, and the reaction was maintained for 8 h. The mixture after the reaction was filtered, washed until the pH of the solution was neutral, and dried at 100 °C to obtain Pt / C catalyst D1 with a Pt loading of 40 wt%.

[0207] Following the method described in the test example, the prepared Pt / C catalyst D1 was applied to the oxygen reduction reaction (ORR) to test its catalytic performance. The corresponding catalytic performance is shown in Table 1.

[0208] Table 1

[0209]

[0210]

[0211] Test Example 2

[0212] This test case illustrates the preparation and electrochemical performance of lithium-ion battery electrodes.

[0213] Preparation of lithium-ion battery electrodes:

[0214] The electrode sheet is composed of an active material (nitrogen-doped carbon material prepared in Examples 4 and 5, respectively), a conductive agent (acetylene black), and a binder, polyvinylidene fluoride (PVDF), in a ratio of 7:1:2. First, a 7% (w / w) N-methylpyrrolidone (NMP) solution of PVDF was prepared. Next, the active material and acetylene black were weighed according to the above ratio, ground and mixed evenly, and then dried in a vacuum oven at 110°C for 10 hours. After cooling, the PVDF solution in the above ratio was added to the mixture, and a small amount of NMP was added dropwise to adjust the slurry. After mixing evenly, the mixture was coated onto copper foil. Finally, the coated copper foil was transferred to a vacuum drying oven at 110°C and dried for 10 hours. After cooling, electrode sheets with a diameter of 1 cm and an area of ​​0.785 cm² were cut using a punch. 2 The sample is weighed after being kept under a pressure of 10 MPa for 5 minutes. Typically, the mass of the electrode sheet is 1-1.5 mg / cm³. 3 .

[0215] Assembly of lithium-ion batteries:

[0216] In a glove box filled with high-purity Ar gas (O2 mass fraction < 10%) -6 H2O mass fraction <10 -6 Assemble a lithium-ion half-cell. Using an electrode coated with active material as the negative electrode, a high-purity lithium sheet as the positive electrode, a Celgard 2400 polypropylene membrane as the separator, and a 1 mol / L LiPF6 solution of ethylene carbonate-dimethyl carbonate-ethyl methyl carbonate (volume ratio 1:1:1) as the electrolyte, assemble a CR 2032 type lithium-ion battery.

[0217] The electrochemical performance of the coin cell fabricated using the nitrogen-doped carbon material of Example 4 is as follows: Figure 16As shown, the electrochemical performance of the coin cell fabricated using the nitrogen-doped carbon material of Example 5 is as follows: Figure 17 As shown in the figure, the initial charge specific capacity, initial discharge specific capacity, first-cycle coulombic efficiency, and capacity retention rate after 100 cycles can be calculated from the figure.

[0218] Among them, the coin cell made with nitrogen-doped carbon material in Example 4 has an initial reversible capacity of 473.7 mAh / g and a capacity retention rate of 85.2% after 100 cycles.

[0219] The coin cell made using the nitrogen-doped carbon material of Example 5 had an initial reversible capacity of 420.9 mAh / g and a capacity retention of 88.5% after 100 cycles.

[0220] As can be seen from the above data, the low resistivity nitrogen-doped carbon material provided by the present invention exhibits good reversible capacity and cycle stability.

[0221] In summary, the nitrogen-doped carbon material provided by this invention has a large specific surface area, increasing the number of active sites, while also exhibiting low resistivity (not exceeding 500 mΩ·cm) and good electrical conductivity. Preferably, the material has a high degree of graphitization. When applied to fuel cell catalysts, the nitrogen-doped carbon material provided by this invention demonstrates excellent catalytic performance; when applied to lithium-ion batteries, it exhibits good reversible capacity and cycle stability.

[0222] 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 proton exchange membrane fuel cell catalyst, the catalyst comprising a support and metal Pt supported on the support, wherein the support is a low resistivity nitrogen-doped carbon material, the carbon material is hollow cage-like, and the molar content of carbon in the carbon material, as determined by X-ray photoelectron spectroscopy, is 93.03-98%, the molar content of nitrogen is 0.5-1.74%, and the molar content of oxygen is 0.5-5.23%; the resistivity of the carbon material is not higher than 500 mΩ·cm, and the specific surface area of ​​the carbon material is 50-1000 m² / m². 2 / g; The carbon material has a dual mesoporous distribution peak, and the dual mesoporous distribution peaks correspond to a first most probable pore size and a second most probable pore size, respectively. The first most probable pore size is 3.5-4 nanometers, and the second most probable pore size is 5-20 nanometers. The hollow cage-like structure is a hollow sphere or near-sphere formed by a graphitized carbon layer surrounding it; The method for preparing the low resistivity nitrogen-doped carbon material includes the following steps: (1) Provide a solution containing a transition metal salt, a polycarboxylic acid and a nitrogen-containing compound, and then dry it to obtain a precursor material; (2) Under an inert or reducing atmosphere, the precursor material obtained in step (1) is subjected to high-temperature pyrolysis at a temperature of 900-1200℃ to obtain pyrolysis products. (3) The pyrolysis product is acid washed, then solid-liquid separation, washing and drying are performed.

2. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, The molar content of carbon in the carbon material was determined by X-ray photoelectron spectroscopy to be 93.03-97.65%, the molar content of nitrogen was 0.9-1.74%, and the molar content of oxygen was 1-5.23%.

3. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, The resistivity of the carbon material is 40-500 mΩ·cm; and / or, the specific surface area of ​​the carbon material is 200-1000 m² / cm². 2 / g.

4. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, The diameter of the carbon material is 2-200 nm.

5. The proton exchange membrane fuel cell catalyst according to claim 4, wherein, The diameter of the carbon material is 5-50 nm.

6. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, In the Raman curve of the carbon material, I D / I G The range is 0.2-1.2; and / or In the X-ray photoelectron spectrum of the carbon material, there is a corresponding... The oxygen content determined by the spectral peaks of the functional group is related to the content determined by the corresponding group. The molar ratio of oxygen content determined by the spectral peaks of the functional groups is 0.01-1.2:

1.

7. The proton exchange membrane fuel cell catalyst according to claim 6, wherein, In the Raman curve of the carbon material, I D / I G The range is 0.3-1.2; and / or In the X-ray photoelectron spectrum of the carbon material, there is a corresponding... The oxygen content determined by the spectral peaks of the functional group is related to the content determined by the corresponding group. The molar ratio of oxygen content determined by the spectral peaks of the functional groups is 0.1-1:

1.

8. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.1-100:0-100; and / or The transition metal is a Group VIII metal; and / or The transition metal salt is one or more of the following: organic acid salts of transition metals, carbonates of transition metals, and basic carbonates of transition metals; and / or The polycarboxylic acid is selected from at least one of citric acid, maleic acid, trimesic acid, terephthalic acid, malic acid, ethylenediaminetetraacetic acid, and pyridinedicarboxylic acid; and / or The nitrogen-containing compound is selected from at least one of urea, melamine, dicyandiamine, hexamethylenetetramine, and amino acids; and / or In step (1), the solvent in the solution is water and / or ethanol.

9. The proton exchange membrane fuel cell catalyst according to claim 8, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.5-5:0.1-5; and / or The transition metal is at least one of iron, cobalt, nickel, and copper; and / or The transition metal salt is an organic acid salt of a transition metal.

10. The proton exchange membrane fuel cell catalyst according to claim 9, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.5-2:0.2-2; and / or The transition metal is nickel.

11. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, In step (2), The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 0.5-30℃ / min and maintaining a constant temperature; and / or The constant temperature time is 20-600 min.

12. The proton exchange membrane fuel cell catalyst according to claim 11, wherein, The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 1-10℃ / min, and maintaining a constant temperature; and / or The constant temperature time is 60-480 minutes.

13. The proton exchange membrane fuel cell catalyst according to claim 12, wherein, The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 5-10℃ / min and maintaining a constant temperature.

14. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, The inert atmosphere is provided by at least one of nitrogen, argon, neon, and helium; and / or, The reducing atmosphere is provided by hydrogen and optionally an inert gas.

15. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, In step (3), the pyrolysis product is acid-washed using an aqueous solution of inorganic acid and / or an aqueous solution of organic acid.

16. The proton exchange membrane fuel cell catalyst according to claim 15, wherein, The aqueous solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, and citric acid.

17. The proton exchange membrane fuel cell catalyst according to claim 16, wherein, The aqueous solution is a hydrochloric acid solution.

18. The proton exchange membrane fuel cell catalyst according to claim 15, wherein, The pH value of the inorganic acid aqueous solution or the organic acid aqueous solution is less than 7.

19. The proton exchange membrane fuel cell catalyst according to claim 1, wherein, In step (3), the pickling temperature is 20-120℃ and the time is 0.1-48h.

20. The proton exchange membrane fuel cell catalyst according to claim 19, wherein, In step (3), the pickling temperature is 60-100℃ and the time is 4-12h.

21. A lithium-ion battery electrode material, wherein the electrode material contains nitrogen-doped carbon material, the carbon material being hollow cage-like, and the molar content of carbon in the carbon material, as determined by X-ray photoelectron spectroscopy, is 93.03-98%, the molar content of nitrogen is 0.5-1.74%, and the molar content of oxygen is 0.5-5.23%; the resistivity of the carbon material is not higher than 500 mΩ·cm, and the specific surface area of ​​the carbon material is 50-1000 m². 2 / g; The carbon material has a dual mesoporous distribution peak, and the dual mesoporous distribution peaks correspond to a first most probable pore size and a second most probable pore size, respectively. The first most probable pore size is 3.5-4 nanometers, and the second most probable pore size is 5-20 nanometers. The hollow cage-like structure is a hollow sphere or near-sphere formed by a graphitized carbon layer surrounding it; The method for preparing the nitrogen-doped carbon material includes the following steps: (1) Provide a solution containing a transition metal salt, a polycarboxylic acid and a nitrogen-containing compound, and then dry it to obtain a precursor material; (2) Under an inert or reducing atmosphere, the precursor material obtained in step (1) is subjected to high-temperature pyrolysis at a temperature of 900-1200℃ to obtain pyrolysis products. (3) The pyrolysis product is acid washed, then solid-liquid separation, washing and drying are performed.

22. The lithium-ion battery electrode material according to claim 21, wherein, The molar content of carbon in the carbon material was determined by X-ray photoelectron spectroscopy to be 93.03-97.65%, the molar content of nitrogen was 0.9-1.74%, and the molar content of oxygen was 1-5.23%.

23. The lithium-ion battery electrode material according to claim 21, wherein, The resistivity of the carbon material is 40-500 mΩ·cm; and / or, the specific surface area of ​​the carbon material is 200-1000 m² / cm². 2 / g.

24. The lithium-ion battery electrode material according to claim 21, wherein, The diameter of the carbon material is 2-200 nm.

25. The lithium-ion battery electrode material according to claim 24, wherein, The diameter of the carbon material is 5-50 nm.

26. The lithium-ion battery electrode material according to claim 21, wherein, In the Raman curve of the carbon material, I D / I G The range is 0.2-1.2; and / or In the X-ray photoelectron spectrum of the carbon material, there is a corresponding... The oxygen content determined by the spectral peaks of the functional group is related to the content determined by the corresponding group. The molar ratio of oxygen content determined by the spectral peaks of the functional groups is 0.01-1.2:

1.

27. The lithium-ion battery electrode material according to claim 26, wherein, In the Raman curve of the carbon material, I D / I G The range is 0.3-1.2; and / or In the X-ray photoelectron spectrum of the carbon material, there is a corresponding... The oxygen content determined by the spectral peaks of the functional group is related to the content determined by the corresponding group. The molar ratio of oxygen content determined by the spectral peaks of the functional groups is 0.1-1:

1.

28. The lithium-ion battery electrode material according to claim 21, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.1-100:0-100; and / or The transition metal is a Group VIII metal; and / or The transition metal salt is one or more of the following: organic acid salts of transition metals, carbonates of transition metals, and basic carbonates of transition metals; and / or The polycarboxylic acid is selected from at least one of citric acid, maleic acid, trimesic acid, terephthalic acid, malic acid, ethylenediaminetetraacetic acid, and pyridinedicarboxylic acid; and / or The nitrogen-containing compound is selected from at least one of urea, melamine, dicyandiamine, hexamethylenetetramine, and amino acids; and / or In step (1), the solvent in the solution is water and / or ethanol.

29. The lithium-ion battery electrode material according to claim 28, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.5-5:0.1-5; and / or The transition metal is at least one of iron, cobalt, nickel, and copper; and / or The transition metal salt is an organic acid salt of a transition metal.

30. The lithium-ion battery electrode material according to claim 29, wherein, In step (1), the mass ratio of transition metal salt, polycarboxylic acid, and nitrogen-containing compound is 1:0.5-2:0.2-2; and / or The transition metal is nickel.

31. The lithium-ion battery electrode material according to claim 21, wherein, In step (2), The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 0.5-30℃ / min and maintaining a constant temperature; and / or The constant temperature time is 20-600 min.

32. The lithium-ion battery electrode material according to claim 31, wherein, The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 1-10℃ / min, and maintaining a constant temperature; and / or The constant temperature time is 60-480 minutes.

33. The lithium-ion battery electrode material according to claim 32, wherein, The high-temperature pyrolysis process includes: heating to the high-temperature pyrolysis temperature at a rate of 5-10℃ / min and maintaining a constant temperature.

34. The lithium-ion battery electrode material according to claim 21, wherein, The inert atmosphere is provided by at least one of nitrogen, argon, neon, and helium; and / or, The reducing atmosphere is provided by hydrogen and optionally an inert gas.

35. The lithium-ion battery electrode material according to claim 21, wherein, In step (3), the pyrolysis product is acid-washed using an aqueous solution of inorganic acid and / or an aqueous solution of organic acid.

36. The lithium-ion battery electrode material according to claim 35, wherein, The aqueous solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, and citric acid.

37. The lithium-ion battery electrode material according to claim 36, wherein, The aqueous solution is a hydrochloric acid solution.

38. The lithium-ion battery electrode material according to claim 35, wherein, The pH value of the inorganic acid aqueous solution or the organic acid aqueous solution is less than 7.

39. The lithium-ion battery electrode material according to claim 21, wherein, In step (3), the pickling temperature is 20-120℃ and the time is 0.1-48h.

40. The lithium-ion battery electrode material according to claim 39, wherein, In step (3), the pickling temperature is 60-100℃ and the time is 4-12h.

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