Carbon materials, their preparation methods, and fuel cells

Abstract

This application relates to the field of fuel cells, and provides a carbon material, a preparation method thereof, and a fuel cell. The carbon material includes carbon particles, and the surface of the carbon particles includes a plurality of interconnected carbon crystallites, and grain boundaries are formed between adjacent two carbon crystallites; the grain boundary density on the surface of the carbon particles is p, 1≤p≤15; wherein, the grain boundary density is obtained by the following test method: randomly obtain 20 carbon powder particles, and through Raman spectroscopy test, measure the peak area I of the carbon characteristic peak of the carbon powder particles D and the peak area I of the graphite characteristic peak G The ratio I D / I G is R n , n = 1, 2, 3…20; the average value of I D / I G of 20 carbon powder particles is R; the grain boundary density #imgabs0#D is the average particle size of the carbon particles. For the carbon material, the preparation method thereof, and the fuel cell provided by this application, the smaller the grain boundary density on the surface of the carbon particles, the fewer the easily corroded sites on the surface of the carbon particles, and the higher the corrosion resistance, which can effectively improve the service life of the carbon material.

Description

Technical Field

[0001] The present application relates to the technical field of fuel cells, and more specifically, to carbon materials, their preparation methods, and fuel cells. Background Art

[0002] Existing fuel cells mainly include multiple battery cells with gas diffusion layers. The gas diffusion layer includes a microporous layer and a substrate. The microporous layer is mainly composed of high-structured carbon materials, which play roles of gas transmission, water drainage, and electron transport in fuel cells. The physicochemical properties such as hydrophilicity-hydrophobicity, conductivity, and pore structure of the microporous layer directly affect the performance of the battery. The working environment of the microporous layer will have high potential and high humidity conditions, and the carbon materials are prone to electrochemical corrosion. After the carbon materials in the microporous layer are corroded, the hydrophilicity-hydrophobicity and pore structure of the materials change, the water drainage and gas transmission functions decline, and the contact resistance between component interfaces increases, accelerating the performance decay of the battery. Therefore, the electrochemical stability of the carbon materials used in the microporous layer determines the operating life of the battery to a certain extent.

[0003] Existing microporous layers mainly use common conductive carbon blacks in the market, such as furnace black, acetylene black, and Ketjen black, as the main materials. There are many defective interfaces in the particles of this type of carbon black material, which are prone to electrochemical corrosion and will accelerate the deterioration of the carbon materials.

[0004] Therefore, a carbon material is needed that can exhibit good functions of gas transmission, water drainage, and electron transport in fuel cells, and at the same time has high resistance to electrochemical corrosion to improve the service life of the battery. Summary of the Invention

[0005] In view of this, the present application provides a carbon material, its preparation method, gas diffusion layer, and fuel cell. The carbon particles have few easily corroded sites on the surface and high corrosion resistance, which can effectively improve the service life of the carbon material.

[0006] In a first aspect, an embodiment of the present application provides a carbon material, the carbon material includes carbon particles, and the surface of the carbon particles includes a plurality of connected carbon crystallites, and a grain boundary is formed between adjacent two carbon crystallites;

[0007] The grain boundary density on the surface of the carbon particles is p, and 1 ≤ p ≤ 15;

[0008] Among them, the grain boundary density is obtained through the following test method:

[0009] Randomly obtain 20 carbon particles, and through Raman spectroscopy test, measure the peak area I D of the carbon characteristic peak of the carbon particles and the peak area I G of the graphite characteristic peak, and the ratio I D / I G is R n, n = 1, 2, 3…20; the average value of I of 20 carbon particles D / I G is R;

[0010] Grain boundary density D is the average particle size of the carbon particles.

[0011] In some embodiments, the carbon particles are spherical or quasi-spherical.

[0012] In some embodiments, the average particle size of the carbon particles is D, 20 nm ≤ D ≤ 200 nm.

[0013] In some embodiments, the carbon crystallites are formed by stacking carbon layers.

[0014] In some embodiments, the average particle size of the carbon crystallites is La, 3 nm ≤ La ≤ 30 nm.

[0015] In some embodiments, through X-ray powder diffraction test, the interplanar spacing of the graphite phase {002} of the carbon material is measured as d 002 nm; the powder conductivity of the carbon material under a pressure of 2.5 kN / cm 2 is σ S / m, and σ / d 002 ≥ 2×10 8 S / cm 2 .

[0016] In some embodiments, the interplanar spacing of the graphite phase {002} of the carbon material is d 002 nm, 0.338 ≤ d 002 ≤ 0.345..

[0017] In some embodiments, the powder conductivity of the carbon material under a pressure of 2.5 kN / cm 2 is σ S / m, σ ≥ 7.

[0018] In some embodiments, the average particle size of the carbon material is 20 nm to 200 nm.

[0019] In some embodiments, the porosity of the carbon material ≥ 60%.

[0020] In some embodiments, the powder contact angle of the carbon material is 120° to 155°.

[0021] In some embodiments, the specific surface area of the carbon material is 30 m 2 / g to 250 m 2 / g.

[0022] In some embodiments, the oil absorption value of the carbon material is 100 mL / 100 g to 450 mL / 100 g.

[0023] In a second aspect, an embodiment of the present application provides a method for preparing a carbon material, including the following steps:

[0024] Placing a mixed material containing a carbon black material and a defect repair agent at 1800 °C to 3000 °C for carbonization treatment, and then performing shaping treatment;

[0025] In an atmosphere containing a modification gas, subjecting the shaped product to surface modification treatment to obtain the carbon material.

[0026] In some embodiments, the boiling point of the defect repair agent is 50 °C to 400 °C.

[0027] In some embodiments, the defect repair agent includes volatile organic compounds and / or semi-volatile organic compounds.

[0028] In some embodiments, the defect repair agent includes volatile organic compounds, and the volatile organic compounds include at least one of camphor, phenol, phthalaldehyde, m-phthalaldehyde, p-phthalaldehyde, p-benzoquinone, benzoic acid, palm alcohol, aminoquinoline, and naphthalene.

[0029] In some embodiments, the defect repair agent includes semi-volatile organic compounds, and the semi-volatile organic compounds include at least one of hydroquinone, phthalic acid, m-phthalaldehyde, and anthracene.

[0030] In some embodiments, before placing the mixed material containing the carbon black material and the defect repair agent at 1800 °C to 3000 °C for carbonization treatment, the method further includes performing shaping treatment on the defect repair agent, and mixing the shaped repair agent with the carbon black material to obtain a mixed material.

[0031] In some embodiments, the average particle size of the defect repair agent is 0.1 μm to 1 μm.

[0032] In some embodiments, the mass ratio of the carbon black material to the defect repair agent is 10:(0.1 to 2).

[0033] In some embodiments, the average particle size of the carbon black material is 20 nm to 200 nm.

[0034] In some embodiments, the oil absorption value of the carbon black material is 100 mL / 100 g to 450 mL / 100 g.

[0035] In some embodiments, through Raman spectroscopy testing, the carbon black material has a carbon characteristic peak I D and a graphite characteristic peak IG ,I D / I G ≤2.0。

[0036] In some embodiments, the powder conductivity σ of the carbon black material under a pressure of 2.5 kN / cm 2 is ≥ 8 S / m.

[0037] In some embodiments, the carbonization treatment time is 0.1 h to 3 h.

[0038] In some embodiments, the heating rate of the carbonization treatment is 2 °C / min to 30 °C / min.

[0039] In some embodiments, the shaping treatment includes at least one of ball milling, sand milling, roller milling, stirred milling, tumbling milling, and planetary milling.

[0040] In some embodiments, before the surface modification treatment of the shaping treatment product, the method further includes: screening the shaping treatment product.

[0041] In some embodiments, the modifying gas includes at least one of carbon dioxide, air, water vapor, oxygen, nitrogen, and ammonia.

[0042] In some embodiments, the atmosphere further includes an inert gas, and the inert gas includes at least one of argon, neon, helium, and krypton.

[0043] In some embodiments, the volume ratio of the modifying gas to the inert gas in the atmosphere is (0.5 to 10):10.

[0044] In some embodiments, the temperature of the surface modification treatment is 400 °C to 1700 °C, and the temperature of the surface modification treatment is preferably 500 °C to 1200 °C.

[0045] In some embodiments, the heating rate of the surface modification treatment is 2 °C / min to 30 °C / min.

[0046] In a third aspect, the present application provides a fuel cell, the fuel cell includes a plurality of cell units having a gas diffusion layer, and the gas diffusion layer includes the above carbon material or the carbon material prepared according to the above preparation method.

[0047] The technical solution of the present application has at least the following beneficial effects:

[0048] First, for the carbon material provided in this application, when the grain boundary density between the carbon grains on the surface of the carbon material particles is smaller, the number of easily corroded sites on the carbon particle surface is less, which can effectively improve the service life of the carbon material; the smaller the surface grain boundary density of the carbon particles, the better the hydrophobicity, and the moisture generated by the reaction is not easily aggregated in the pores of the carbon material, which is beneficial to maintaining the gas conduction ability of the pore structure of the microporous layer composed of this material, and improving the battery performance of the battery under the conditions of high humidity and high current density. And the carbon material has both high electrical conductivity and high graphitization degree. The better the electrical conductivity performance of the carbon material, the stronger the electron transport performance of the carbon material and the lower the power loss; the higher the graphitization degree of the carbon material, the higher the corrosion resistance of the material. Thus, the gas diffusion layer prepared from this material has a high electrochemical conversion efficiency at high current density and has the characteristics of a long service life.

[0049] Secondly, for the preparation method provided in this application, the mixed material containing carbon black material and defect repair agent is placed at 1800°C to 3000°C for carbonization treatment. During the carbonization treatment at an ultra-high temperature, the defect repair agent can decompose to generate carbon free radicals or carbene structures, which are typical electron-deficient neutral active intermediates and can be deposited on the surface of carbon particles to repair the defects on the surface of carbon particles, which is beneficial to obtaining carbon particles with a lower surface grain boundary density, and is beneficial to obtaining a carbon material with high graphitization, high electrical conductivity, and high durability; then shaping treatment is carried out, which can reduce the powder particle size of the carbon material and is beneficial to preparing a gas diffusion layer with a flat surface and a uniform distribution of microporous layer carbon materials. Carrying out surface modification treatment on the product after shaping treatment can improve the structural orderliness of the carbon material surface and improve the anti-chemical and electrochemical corrosion abilities, etc. The entire preparation process is simple, which can effectively improve the high electrical conductivity performance and high hydrophobic durability performance of the material, improve the service life of the carbon material, and reduce the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic structural diagram of the carbon material provided by the embodiment of this application;

[0051] Figure 2 It is a schematic flow diagram of the carbon material preparation method provided by the embodiment of this application;

[0052] Figure 3 It is a thermogravimetric diagram of the carbon materials of Example 1, 3 and Comparative Example 1;

[0053] Figure 4 It is an electrochemical potentiostatic polarization curve diagram of the carbon materials of Example 1, 3 and Comparative Example 1 coated to prepare a fuel cell gas diffusion layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The following is the implementation manner of the embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principles of the embodiments of the present invention, several improvements and retouches can be made, and these improvements and retouches are also regarded as the protection scope of the embodiments of the present invention.

[0055] The present application provides a carbon material, which includes carbon particles. The surface of the carbon particles includes a plurality of connected carbon crystallites, and grain boundaries are formed between adjacent two carbon crystallites.

[0056] The grain boundary density on the surface of the carbon particles is p, where 1 ≤ p ≤ 15.

[0057] Among them, the grain boundary density is obtained by the following test method:

[0058] Randomly obtain 20 portions of carbon particles. Through Raman spectroscopy test, the peak area I of the carbon characteristic peak of the carbon particles is measured. D And the peak area I of the graphite characteristic peak G The ratio I D / I G The value of is R n , n = 1, 2, 3... 20; The average value of I D / I G of the 20 portions of carbon particles is R.

[0059] The grain boundary density D is the average particle size of the carbon particles.

[0060] In the above solution, when the grain boundary density between the carbon crystallites on the surface of the carbon material particles is smaller, the number of easily corroded sites on the surface of the carbon particles is less, which can effectively improve the service life of the carbon material; the smaller the surface grain boundary density of the carbon particles, the better the hydrophobicity, and the moisture generated by the reaction is not easy to accumulate in the pores of the carbon material, which is beneficial to maintaining the gas conduction ability of the pore structure of the microporous layer composed of this material and improving the battery performance of the battery under the conditions of high humidity and high current density. And the carbon material has both high electrical conductivity and high graphitization degree. The better the electrical conductivity performance of the carbon material, the stronger the electron transport performance of the carbon material and the lower the power loss; the higher the graphitization degree of the carbon material, the higher the corrosion resistance of the material. Thus, the gas diffusion layer made of this material has a high electrochemical conversion efficiency at high current density and has the characteristics of a long service life.

[0061] It can be understood that the carbon particles are primary particles, and the primary particles can agglomerate to form secondary particles.

[0062] In some implementation manners, the peak area I of the carbon characteristic peak of the carbon particles D And the peak area I of the graphite characteristic peak G , 0.15 ≤ I D / I G ≤ 1.5.

[0063] In some embodiments, the grain boundary density p can specifically be 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, etc., which is not limited herein. Preferably, 1 ≤ p ≤ 10. It can be understood that the corrosion of the carbon material usually starts along the grain boundary positions on the surface of the carbon particles. The smaller the grain boundary density on the surface of the carbon particles, the fewer the easily corroded sites on the surface, and the longer the service life of the carbon material can be. The carbon black materials in the prior art have more grain boundaries on the surface and it is difficult to achieve the state of a complete grain boundary-free fullerene-like structure.

[0064] Grain boundary density The specific evolution process is as follows:

[0065] If the average particle size of the carbon particles is D and the carbon particles are spherical or quasi-spherical, then the circumference of the largest cross-sectional circle of the carbon particles is Dπ, and the outer surface area of the carbon particles is D 2 π.

[0066] The average particle size of the carbon crystallites can be measured by Raman spectroscopy. The peak area I D of the carbon characteristic peak of the carbon particles and the peak area I G of the graphite characteristic peak D The average value of the ratio I G / I

[0067] In some embodiments, as Figure 1 shown, the average particle size of the carbon crystallites is La, and 3 nm ≤ La ≤ 30 nm; specifically, it can be 3 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, or 30 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. Controlling the average particle size of the carbon crystallites within the above range can reduce the grain boundary density between the carbon crystallites, reduce defects, and enhance the corrosion resistance of the carbon material. Preferably, 5 nm ≤ La ≤ 20 nm.

[0068] In some embodiments, the carbon particles are spherical or quasi-spherical. In some embodiments, the carbon crystallites are formed by stacking carbon layers.

[0069] Since the surface of the carbon particles includes a plurality of connected carbon crystallites, then, the sum of the surface areas of each carbon crystallite gives the outer surface area of the carbon particles, that is, the number of carbon crystallites n = the outer surface area of the carbon particles / the surface area of the carbon crystallite, and its calculation formula is as shown in the following formula:

[0070] The grain boundary density of the carbon particles = (number of carbon grains * average surface grain perimeter / 2) / average single particle perimeter, and its calculation formula is as shown below:

[0071] In some embodiments, the average particle size of the carbon particles is D, where 20 nm ≤ D ≤ 200 nm; specifically, it can be 20 nm, 50 nm, 60 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, 200 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. Controlling the average particle size of the carbon particles within the above range is beneficial to obtaining a carbon material with a good drainage and gas transmission pore structure, facilitating the formation of a gas diffusion layer with a flat surface, and reducing the contact resistance between the gas diffusion layer and the catalytic layer. Preferably, 30 nm ≤ D ≤ 100 nm.

[0072] In some embodiments, the particle size D of the carbon material 90 ≤ 200 μm, preferably, D 90 ≤ 100 μm. If the D of the carbon material 90 is too large, it is not conducive to the formation of a gas diffusion layer with a flat surface. Carbon particles of appropriate size can form a gas diffusion layer with a flat surface and reduce the contact resistance between the gas diffusion layer and the catalytic layer.

[0073] In some embodiments, the carbon material has a high degree of crystallinity of the graphite phase and high electrical conductivity characteristics.

[0074] In some embodiments, through X-ray powder diffraction testing, the interplanar spacing of the graphite phase {002} of the carbon material is measured as d 002 nm; the powder conductivity of the carbon material under a pressure of 2.5 kN / cm 2 is σ (S / m), and σ / d 002 ≥ 2 * 10 8 S / cm 2 . The ratio of the powder conductivity to the interplanar spacing can be used to characterize the high degree of graphitization and high electrical conductivity characteristics of the carbon material. It can be understood that the higher the degree of graphitization of the carbon material, the higher the corrosion resistance of the carbon material; the better the electrical conductivity performance of the carbon material, the stronger the electron transport performance of the carbon material, and the lower the power loss. Preferably, σ / d 002 ≥ 3 * 10 8 S / cm 2 . Therefore, the powder conductivity and interplanar spacing of the carbon material of the present application can be controlled within the above range, and the carbon material can have both high electrical conductivity characteristics and a longer service life.

[0075] Among them, through X-ray powder diffraction test, the diffraction peak angle of the {002} crystal plane of the carbon material is measured, and the interlayer spacing d of the {002} crystal plane of the carbon material is calculated by the Bragg equation 2dsinθ = nλ. 002 The value;

[0076] In some embodiments, the interlayer spacing of the {002} crystal plane of the carbon particles is d 002 , 0.338 nm ≤ d 200 ≤ 0.345 nm; specifically, it can be 0.338 nm, 0.339 nm, 0.340 nm, 0.341 nm, 0.342 nm, 0.343 nm, 0.344 nm or 0.345 nm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The smaller the interlayer spacing of the carbon particles, the higher the crystallinity of the carbon material.

[0077] In some embodiments, through powder conductivity test, when a pressure of 2.5 kN is applied to the carbon material, the powder conductivity of the carbon material is measured as σ, and σ ≥ 7 S / m; specifically, it can be 7 S / m, 7.5 S / m, 7.9 S / m, 8.5 S / m, 8.9 S / m, 9.5 S / m, 10.0 S / m or 11.0 S / m, etc., but not limited to the listed values. The higher the conductivity of the carbon material, the smaller the electron transport resistance of the material, and the higher the performance of the gas diffusion layer battery made of this carbon material.

[0078] In some embodiments, the porosity of the carbon material ≥ 60%, specifically, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, etc., which is not limited herein. The higher the porosity of the carbon material, the more conducive to the diffusion of reactive gases in the gas diffusion layer. Preferably, the porosity of the carbon material ≥ 80%.

[0079] In some embodiments, the powder contact angle of the carbon material is 120° - 155°, specifically, it can be 120°, 125°, 130°, 135°, 140°, 145°, 150° or 155°, etc., which is not limited herein. Controlling the powder contact angle of the carbon material within the above range is conducive to improving the hydrophobic performance of the material, and the moisture generated by the reaction is not easily aggregated in the pores of the carbon material, thereby avoiding corrosion of the carbon particles and improving the service life of the carbon material.

[0080] In some embodiments, the specific surface area of the carbon material is 30 m 2 / g - 250 m 2 / g; optionally, the specific surface area ratio of the composite negative electrode material can be 30 m 2 / g, 40 m 2 / g, 60 m 2 / g, 80 m 2 / g, 100m 2 / g, 120m 2 / g, 140m 2 / g, 160m 2 / g, 180m 2 / g, 200m 2 / g or 250m 2 / g etc., which are not limited herein; it can be understood that controlling the specific surface area within the above range is beneficial for the carbon material to have better gas transmission and drainage performance.

[0081] In some embodiments, the oil absorption value of the carbon material is 100 mL / 100 g to 450 mL / 100 g. Specifically, it can be 100 mL / 100 g, 200 mL / 100 g, 250 mL / 100 g, 300 mL / 100 g, 350 mL / 100 g, 400 mL / 100 g or 450 mL / 100 g. The higher the oil absorption value of the carbon material, the better the gas transmission and drainage performance of the carbon material. Considering the mass transfer performance of the material, preferably, the oil absorption value of the carbon material is 250 mL / 100 g to 400 mL / 100 g.

[0082] In some embodiments, the average particle size of the carbon material is 0.1 μm to 10 μm. Specifically, it can be 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm or 10 μm etc., which are not limited herein.

[0083] This application also provides a preparation method of a carbon material, as Figure 2 shown, including the following steps:

[0084] Step S1, placing the mixed material containing carbon black material and defect repair agent at 1800 °C to 3000 °C for carbonization treatment, and then performing shaping treatment;

[0085] Step S2, performing surface modification treatment on the shaped product in an atmosphere containing modified gas to obtain the carbon material.

[0086] In the above solution, the mixed material containing carbon black material and defect repair agent is placed at 1800°C to 3000°C for carbonization treatment. During the carbonization treatment at ultra-high temperature, the defect repair agent can decompose to generate carbon free radicals or carbene structures, which are typical electron-deficient neutral active intermediates and can be deposited on the surface of carbon particles to repair the defects on the surface of carbon particles. This is conducive to obtaining carbon particles with a lower surface grain boundary density, and is conducive to obtaining a carbon material with high graphitization, high electrical conductivity, and high durability; then shaping treatment is carried out, which can reduce the powder particle size of the carbon material and is conducive to preparing a gas diffusion layer with a flat surface and a uniform distribution of microporous layer carbon material. The product after shaping treatment is subjected to surface modification treatment, which can improve the structural orderliness of the carbon material surface and enhance the resistance to chemical and electrochemical corrosion. The entire preparation process is simple, can effectively improve the high electrical conductivity performance and high hydrophobic durability performance of the material, increase the service life of the carbon material, and reduce the preparation cost.

[0087] The following details this solution:

[0088] Before step S1, the method further includes:

[0089] The defect repair agent is subjected to shaping treatment, and the shaped defect repair agent is mixed with the carbon black material to obtain a mixed material.

[0090] In some embodiments, the shaping method of the defect repair agent is grinding, and the grinding time of the defect repair agent is 1h to 6h, so that the average particle size of the shaped defect repair agent reaches 0.1μm to 1μm.

[0091] In some embodiments, the grinding time can specifically be 1h, 2h, 3h, 4h, 5h or 6h, etc. Of course, it can also be other values within the above range, which is not limited here. The specific grinding method can be ball milling, mechanical grinding, etc., which is not limited here.

[0092] In some embodiments, the average particle size of the shaped defect repair agent can specifically be 0.1μm, 0.3μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 1μm, etc., which is not limited here. The particle size in the nanometer range can improve the dispersion degree of the defect repair agent in the carbon black material and can make the defect repair agent volatilize and diffuse evenly more slowly. The repair agent with a smaller particle size will volatilize rapidly during the heating process and lose the function of the repair agent, while the repair agent with a larger particle size is difficult to disperse evenly, resulting in a weakened repair effect.

[0093] In some embodiments, the boiling point of the defect repair agent is 50°C to 400°C, specifically, it can be 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 260°C, 280°C, 320°C, 380°C or 400°C, etc. Of course, it can also be other values within the above range, which are not limited herein. The boiling point of the defect repair agent is relatively low and it is easily decomposed by heat during the high-temperature carbonization process to form carbon free radicals and / or carbene structures. It is a typical electron-deficient neutral active intermediate and can be deposited on the surface of carbon particles to repair the defects on the surface of carbon particles.

[0094] In some embodiments, the defect repair agent includes volatile organic compounds (VOCs) and / or semi-volatile organic compounds (SVOCs). Among them, the boiling point of the volatile organic compounds (VOCs) is 50°C to 260°C, and the boiling point of the semi-volatile organic compounds (SVOCs) is 240°C to 400°C.

[0095] In some embodiments, the defect repair agent includes volatile organic compounds, and the volatile organic compounds include at least one of camphor, phenol, o-phthalaldehyde, m-phthalaldehyde, p-phthalaldehyde, p-benzoquinone, benzoic acid, palm alcohol, aminoquinoline and naphthalene.

[0096] In some embodiments, the defect repair agent includes semi-volatile organic compounds, and the semi-volatile organic compounds include at least one of hydroquinone, phthalic acid, m-phthalaldehyde and anthracene.

[0097] In some embodiments, the mixing treatment method of the shaped defect repair agent and the carbon black material includes at least one of mechanical mixing and stirring mixing. Exemplarily, a mixer is used for mixing to improve the uniformity of the mixed materials.

[0098] In some embodiments, the mixing treatment time is 0.5 h to 3 h, specifically, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0099] Step S1, place the mixed material containing the carbon black material and the defect repair agent at 1800°C to 3000°C for carbonization treatment, and then perform shaping treatment.

[0100] In some embodiments, the mass ratio of the carbon black material to the defect repair agent is 10:(0.1 - 2), specifically it can be 10:0.1, 10:0.3, 10:0.5, 10:0.8, 10:1, 10:1.2, 10:1.5, 10:1.8 or 10:0.2, etc. Of course, it can also be other values within the above range, which are not limited herein. During the carbonization treatment process of the defect repair agent, the carbon free radicals and / or carbene structures formed by thermal decomposition can be deposited on the surface of the carbon particles to repair the defects on the surface of the carbon particles.

[0101] In some embodiments, the average particle size of the carbon black material is 20nm - 200nm, specifically it can be 20nm, 50nm, 60nm, 80nm, 90nm, 100nm, 120nm, 150nm, 180nm, 190nm or 200nm, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0102] In some embodiments, the oil absorption value of the carbon black material is 100mL / 100g - 450mL / 100g; specifically it can be 100mL / 100g, 200mL / 100g, 250mL / 100g, 300mL / 100g, 350mL / 100g, 400mL / 100g or 450mL / 100g, which are not limited herein. Considering the mass transfer performance of the material, preferably, the oil absorption value of the carbon black material is 300mL / 100g - 450mL / 100g.

[0103] In some embodiments, through Raman spectroscopy testing, the carbon black material has a carbon characteristic peak I D and a graphite characteristic peak I G , I D / I G ≤2.0, specifically it can be 2.0, 1.8, 1.6, 1.5, 1.4, 1.2, 1.0, 0.8, 0.6, etc., which are not limited herein.

[0104] In some embodiments, the powder conductivity σ of the carbon black material under a pressure of 2.5kN / cm 2 ≥8S / m, specifically it can be 8S / m, 9S / m, 10S / m, 11S / m, 12S / m, 13S / m, 14S / m or 15S / m, which are not limited herein.

[0105] In some embodiments, the temperature of the carbonization treatment is 1800 °C to 3000 °C; specifically, it can be 1800 °C, 1900 °C, 2000 °C, 2200 °C, 2300 °C, 2350 °C, 2400 °C, 2500 °C, 2600 °C, 2700 °C, 2800 °C or 3000 °C. A higher carbonization temperature is beneficial to highly graphitize the carbon material, thereby forming continuous carbon grains and reducing the grain boundary density on the surface of the carbon material.

[0106] In some embodiments, the time of the carbonization treatment is 0.1 h to 12 h; specifically, it can be 0.1 h, 0.2 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h or 12 h. After sufficient carbonization treatment, the formed carbon material has high crystallinity and high graphitization characteristics.

[0107] In some embodiments, the heating rate of the carbonization treatment is 2 °C / min to 30 °C / min. For example, it can be 2 °C / min, 3 °C / min, 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min or 30 °C / min.

[0108] In some embodiments, the cooling rate after the carbonization treatment is 1 °C / min to 20 °C / min. Specifically, it can be 1 °C / min, 2 °C / min, 3 °C / min, 5 °C / min, 6 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 14 °C / min, 16 °C / min, 18 °C / min or 20 °C / min. After cooling to room temperature, it is okay.

[0109] In some embodiments, the carbonization treatment is carried out under the protection of an inert gas, and the inert gas includes at least one of argon, neon, helium and krypton.

[0110] In some embodiments, the shaping treatment includes at least one of ball milling, sand milling, roller milling, stirred milling, tumbling milling and planetary milling. Preferably, the shaping treatment method is ball milling, and the ball milling time is 0.5 h to 24 h; specifically, it can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 8 h, 12 h, 16 h, 18 h, 20 h or 24 h, etc., but is not limited to the listed values. It can be understood that sufficient shaping treatment can reduce the powder particle size of the carbon material, obtain a more uniform particle size of the carbon material, and is beneficial to preparing a gas diffusion layer with a flat surface and a uniform distribution of the microporous layer carbon material.

[0111] In some embodiments, before the surface modification treatment of the shaping treatment product, the method further includes: screening the shaping treatment product.

[0112] In some embodiments, the screening method includes any one of a fixed screen, a rotary screen, a resonance screen, a roller screen, a vibrating screen, and a chain screen. The mesh number of screening is ≥400 mesh. Specifically, the mesh number of screening can be 400 mesh, 350 mesh, 300 mesh, 250 mesh, 200 mesh, 150 mesh, 100 mesh, 70 mesh, 50 mesh, etc. Controlling the particle size of the material within the above range is beneficial to form a gas diffusion layer with a flat surface.

[0113] Step S2, in an atmosphere containing a modifying gas, subject the shaped product to surface modification treatment to obtain a carbon material.

[0114] In some embodiments, the modifying gas includes at least one of carbon dioxide, air, water vapor, oxygen, nitrogen, and ammonia.

[0115] In some embodiments, the atmosphere further includes an inert gas, and the inert gas includes at least one of argon, neon, helium, and krypton.

[0116] In some embodiments, the volume ratio of the modifying gas to the inert gas in the atmosphere is (0.5 - 10):10; specifically, it can be 0.5:10, 1:10, 2:10, 3:10, 4:10, 5:10, 6:10, 7:10, 8:10, 9:10, or 10:10, etc., which is not limited herein.

[0117] In some embodiments, the temperature of the surface modification treatment is 400°C to 1700°C; specifically, it can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1200°C, 1400°C, 1500°C, 1600°C, or 1700°C. Within this temperature range, it is beneficial to maintain the structural characteristics of the carbonized carbon material from being damaged, and other non-carbon elements can be introduced on the carbon surface for surface modification, improving the structural orderliness of the carbon material surface and enhancing the resistance to chemical and electrochemical corrosion. Preferably, the temperature of the surface modification treatment is 500°C to 1200°C.

[0118] In some embodiments, the time of the surface modification treatment is 0.5 h to 3 h; specifically, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc., but is not limited to the listed values.

[0119] In some embodiments, the heating rate of the surface modification treatment is 2°C / min to 30°C / min; specifically, it can be 2°C / min, 5°C / min, 7°C / min, 10°C / min, 15°C / min, 18°C / min, 20°C / min, 25°C / min, or 30°C / min, etc., but is not limited to the listed values.

[0120] This application provides a fuel cell, which includes a plurality of cell units with gas diffusion layers, and the gas diffusion layer includes the above-mentioned carbon material or the carbon material prepared according to the above-mentioned preparation method.

[0121] The embodiments of the present invention will be further described in multiple embodiments below. Among them, the embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, modifications can be made appropriately.

[0122] Example 1

[0123] (1) Select camphor as the defect repair agent, place the camphor in a ball mill for grinding treatment, roll and grind for 3 h to obtain the ground camphor with an average particle size of 0.5 μm;

[0124] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption value of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I D / I G = 1.53, and the powder conductivity σ = 10.0 S / m under a pressure of 2.5 kN / cm 2 ; Place the carbon black material and the ground camphor in a mixer for mixing. The mass ratio of the carbon black material to camphor is 10:0.5, and the mixing time is 1 h to obtain a mixed material;

[0125] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate to be 10 °C / min, heat up to 1800 °C for high-temperature carbonization treatment for 1 h, and take out the sample after it cools to room temperature.

[0126] (4) Transfer the product after carbonization treatment into a 5 L ball mill, roll and grind for 3 h, break the agglomerated large carbon particles into small carbon particles, and pass the ground carbon material through a 100-mesh sieve; Heat-treat the sieved material in a mixed atmosphere of air and argon at 500 °C for 2 h, and the volume ratio of air to argon is 5:10; Obtain the carbon material.

[0127] The carbon material prepared in this example includes a number of carbon particles, the carbon particles are spherical, and the surface of the carbon particles includes a plurality of connected carbon crystallites. The grain boundary density p on the surface of the carbon particles is 12.7.

[0128] Example 2

[0129] (1) Select camphor as the defect repair agent, place the camphor in a ball mill for grinding treatment, roll and grind for 3 h to obtain the ground camphor with an average particle size of 0.5 μm;

[0130] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I of the carbon black material D / I G = 1.53. At a pressure of 2.5 kN / cm 2 The powder conductivity σ under pressure is 10.0 S / m. Place the carbon black material and the ground camphor in a mixer for mixing. The mass ratio of the carbon black material to camphor is 10:0.5, and the mixing time is 1 h to obtain a mixed material;

[0131] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2200 °C for high-temperature carbonization treatment for 1 h. After the sample cools to room temperature, take it out.

[0132] (4) Transfer the product after carbonization treatment to a 5 L ball mill jar and grind it for 3 h to break the agglomerated large carbon particles into small carbon particles. Pass the ground carbon material through a 100-mesh sieve; heat-treat the sieved carbon material at 500 °C for 2 h in a mixed atmosphere of air and argon, and the volume ratio of air to argon is 5:10; obtain the carbon material.

[0133] The carbon material prepared in this example includes a number of carbon particles. The carbon particles are spherical. The surface of the carbon particles includes a plurality of connected carbon crystallites, and the grain boundary density p on the surface of the carbon particles is 8.7.

[0134] Example 3

[0135] (1) Select camphor as a defect repair agent. Place the camphor in a ball mill jar for grinding treatment and grind it for 4 h to obtain the ground camphor with an average particle size of 1 μm;

[0136] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I of the carbon black material D / I G = 1.53. At a pressure of 2.5 kN / cm 2 The powder conductivity σ under pressure is 10.0 S / m. Place the carbon black material and the ground camphor in a mixer for mixing. The mass ratio of the carbon black material to camphor is 10:0.5, and the mixing time is 2 h to obtain a mixed material;

[0137] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2800 °C for high-temperature carbonization treatment for 1 h. After the sample cools to room temperature, take it out.

[0138] (4) Transfer the product after carbonization treatment into a 5L ball milling jar, and roll and grind for 3h to break the agglomerated large carbon particles into small carbon particles. Pass the ground carbon material through a 100-mesh sieve; heat-treat the sieved carbon material at 500°C for 2h in a mixed atmosphere of air and argon, and the volume ratio of air to argon is 5:10; obtain the carbon material.

[0139] The carbon material prepared in this example includes several carbon particles, the carbon particles are spherical, the surface of the carbon particles includes multiple connected carbon grains, and the grain boundary density p on the surface of the carbon particles is 4.4.

[0140] Example 4

[0141] (1) Select quinoline as the defect repair agent, place quinoline in a ball milling jar for grinding treatment, roll and grind for 6h to obtain the ground quinoline, and its average particle size is 0.5μm;

[0142] (2) Select carbon black material with an average particle size of 35nm and an oil absorption of 350mL / 100g. The carbon characteristic peak and graphite characteristic peak I D / I G =1.53, and the powder conductivity σ under a pressure of 2.5kN / cm 2 is 10.0S / m. Place the carbon black material and the ground quinoline in a mixer for mixing. The mass ratio of the carbon black material to quinoline is 10:0.1, and the mixing time is 2h to obtain the mixed material;

[0143] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate to be 10°C / min, heat up to 3000°C for high-temperature carbonization treatment for 1h, and take out the sample after it cools to room temperature.

[0144] (4) Transfer the product after carbonization treatment into a 5L ball milling jar, and roll and grind for 3h to break the agglomerated large carbon particles into small carbon particles. Pass the ground carbon material through a 100-mesh sieve; heat-treat the sieved carbon material at 500°C for 2h in a mixed atmosphere of air and argon, and the volume ratio of air to argon is 5:10; obtain the carbon material.

[0145] The carbon material prepared in this example includes several carbon particles, the carbon particles are spherical, the surface of the carbon particles includes multiple connected carbon grains, and the grain boundary density p on the surface of the carbon particles is 4.3.

[0146] Example 5

[0147] (1) Select styrene as the defect repair agent, place styrene in a ball milling jar for grinding treatment, roll and grind for 2h to obtain the ground styrene, and its average particle size is 0.5μm;

[0148] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I D / I G = 1.53. Under a pressure of 2.5 kN / cm 2 The powder conductivity σ of the carbon black material is 10.0 S / m. Mix the carbon black material and the ground styrene in a mixer. The mass ratio of the carbon black material to styrene is 10:1, and the mixing time is 3 h to obtain a mixed material;

[0149] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2800 °C for high-temperature carbonization treatment for 1 h. After the sample cools to room temperature, take it out.

[0150] (4) Transfer the product after carbonization treatment to a sand mill and grind it for 5 h to break the agglomerated large carbon particles into small carbon particles. Pass the ground carbon material through a 100-mesh sieve; heat-treat the sieved carbon material in a mixed atmosphere of water vapor and argon at 400 °C for 2 h. The volume ratio of water vapor to argon is 5:10; obtain the carbon material.

[0151] The carbon material prepared in this example includes a number of carbon particles. The carbon particles are spherical. The surface of the carbon particles includes a plurality of connected carbon crystallites. The grain boundary density p on the surface of the carbon particles is 4.8.

[0152] Example 6

[0153] (1) Select phenol as the defect repair agent. Place the phenol in a ball mill for grinding treatment. Roll and grind for 3 h to obtain ground phenol with an average particle size of 0.8 μm;

[0154] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption value of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I D / I G = 1.53. Under a pressure of 2.5 kN / cm 2 The powder conductivity σ of the carbon black material is 10.0 S / m. Mix the carbon black material and the ground phenol in a mixer. The mass ratio of the carbon black material to phenol is 10:2, and the mixing time is 1.5 h to obtain a mixed material;

[0155] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2800 °C for high-temperature carbonization treatment for 1 h. After the sample cools to room temperature, take it out.

[0156] (4) Transfer the product after carbonization treatment into a 5L ball milling jar, and grind it for 3h to break the agglomerated large carbon particles into small carbon particles. Then, sieve the ground carbon material through a 100-mesh sieve. Heat-treat the sieved material in a mixed atmosphere of ammonia and argon at 800 °C for 2h, with the volume ratio of ammonia to argon being 5:10. Obtain carbon material.

[0157] The carbon material prepared in this example comprises a number of carbon particles, which are spherical. The surface of the carbon particles comprises a plurality of connected carbon crystallites, and the grain boundary density p on the surface of the carbon particles is 4.6.

[0158] Example 7

[0159] (1) Select camphor as the defect repair agent, place the camphor in a ball milling jar for grinding treatment, and grind it for 4h to obtain the ground camphor with an average particle size of 1μm.

[0160] (2) Select carbon black material with an average particle size of 35nm and an oil absorption of 350mL / 100g. The carbon characteristic peak and graphite characteristic peak I D / I G = 1.53, and the powder conductivity σ under a pressure of 2.5kN / cm 2 is 10.0S / m. Place the carbon black material and the ground camphor in a mixer for mixing. The mass ratio of the carbon black material to camphor is 10:0.05, and the mixing time is 2h to obtain a mixed material.

[0161] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2800 °C for high-temperature carbonization treatment for 1h. After the sample cools to room temperature, take it out.

[0162] (4) Transfer the product after carbonization treatment into a 5L ball milling jar, and grind it for 3h to break the agglomerated large carbon particles into small carbon particles. Then, sieve the ground carbon material through a 100-mesh sieve. Heat-treat the sieved carbon material in a mixed atmosphere of air and argon at 500 °C for 2h, with the volume ratio of air to argon being 5:10. Obtain carbon material.

[0163] The carbon material prepared in this example comprises secondary particles, and the secondary particles comprise a number of carbon particles, which are spherical. The surface of the carbon particles comprises a plurality of connected carbon crystallites, and the grain boundary density p on the surface of the carbon particles is 6.2.

[0164] Example 8

[0165] (1) Select camphor as the defect repair agent, place the camphor in a ball milling jar for grinding treatment, and perform high-energy ball milling for 4h to obtain the ground camphor with an average particle size of 50nm.

[0166] (2) Select a carbon black material with an average particle size of 35 nm and an oil absorption of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I of the carbon black material D / I G = 1.53, and the powder conductivity σ of the carbon black material under a pressure of 2.5 kN / cm 2 is 10.0 S / m. Place the carbon black material and the ground camphor in a mixer for mixing. The mass ratio of the carbon black material to camphor is 10:0.5, and the mixing time is 2 h to obtain a mixed material;

[0167] (3) Load the mixed material into a graphite crucible and place it in a graphitization furnace. Under an argon atmosphere, control the heating rate at 10 °C / min and heat it to 2800 °C for high-temperature carbonization treatment for 1 h. After the sample cools to room temperature, take it out.

[0168] (4) Transfer the product after carbonization treatment to a 5 L ball mill jar and roll and grind it for 3 h to break the agglomerated large carbon particles into small carbon particles. Pass the ground carbon material through a 100-mesh sieve; heat-treat the sieved carbon material at 500 °C for 2 h in a mixed atmosphere of air and argon, and the volume ratio of air to argon is 5:10; obtain the carbon material.

[0169] The carbon material prepared in this example includes a number of carbon particles, the carbon particles are spherical, and the surface of the carbon particles includes a plurality of connected carbon grains. The grain boundary density p on the surface of the carbon particles is 5.7.

[0170] Comparative Example 1:

[0171] Select a carbon black material with an average particle size of 35 nm and an oil absorption value of 350 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I of the carbon black material D / I G = 1.53, and the powder conductivity σ of the carbon material under a pressure of 2.5 kN / cm 2 is 10.0 S / m as the carbon material.

[0172] Comparative Example 2:

[0173] Select a carbon black material with an average particle size of 36 nm and an oil absorption value of 320 mL / 100 g. The carbon characteristic peak and graphite characteristic peak I of the carbon black material D / I G = 1.46, and the powder conductivity σ of the carbon material under a pressure of 2.5 kN / cm 2 is 12.9 S / m as the carbon material XC72.

[0174] Comparative Example 3:

[0175] The difference from Example 3 is that no defect repair agent is added.

[0176] Comparative Example 4:

[0177] Multi-walled carbon nanotubes with a length of 15 μm and a diameter of 15 nm were selected, and the electrical conductivity σ of the carbon material powder under a pressure of 2.5 kN / cm 2 was 25.6 S / m, which was used as the carbon material.

[0178] Comparative Example 5:

[0179] Single-layer graphene was selected, and the electrical conductivity σ of the carbon material powder under a pressure of 2.5 kN / cm 2 was 27.8 S / m, which was used as the carbon material.

[0180] Comparative Example 6

[0181] (1) Camphor was selected as the defect repair agent, and camphor was placed in a ball mill for grinding treatment. It was roll-milled for 4 h to obtain the ground camphor with an average particle size of 1 μm;

[0182] (2) Carbon black materials with an average particle size of 35 nm and an oil absorption of 350 mL / 100 g were selected. The carbon characteristic peak and graphite characteristic peak I D / I G of the carbon black material was 1.53, and the electrical conductivity σ of the powder under a pressure of 2.5 kN / cm 2 was 10.0 S / m. The carbon black material and the ground camphor were placed in a mixer for mixing. The mass ratio of the carbon black material to camphor was 10:0.5, and the mixing time was 2 h to obtain a mixed material;

[0183] (3) The mixed material was loaded into a graphite crucible and placed in a graphitization furnace. Under an argon atmosphere, the heating rate was controlled at 10 °C / min, and it was heated to 2800 °C for high-temperature carbonization treatment for 1 h. After the sample was cooled to room temperature, it was taken out.

[0184] Testing:

[0185] 1) Particle size test method for carbon materials:

[0186] The particle size test method refers to GB / T 19077-2016. It can be conveniently measured with a laser particle size analyzer, such as the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited in the UK.

[0187] 2) Specific surface area test method for carbon materials:

[0188] At a constant low temperature, after measuring the adsorption amount of gas on the solid surface at different relative pressures, the monolayer adsorption amount of the sample was obtained based on the Brunauer-Emmett-Teller adsorption theory and its formula (BET formula), and thus the specific surface area of the material was calculated.

[0189] 3) Test method for the average particle size La of carbon grains and grain boundary density:

[0190] Randomly obtain 20 carbon particles, and through Raman spectroscopy testing (Raman laser wavelength λ = 514 nm), measure the peak area I of the carbon characteristic peak of the carbon particles D and the peak area I of the graphite characteristic peak G The ratio I D / I G is R n , n = 1, 2, 3…20; the average value of I D / I G of the 20 carbon particles is R;

[0191] The average particle size La of carbon grains = 4.4 / R;

[0192] Grain boundary density D is the average particle size of the carbon particles.

[0193] 4) Test method for the interlayer spacing d of the crystal layer 002 :

[0194] Measure the diffraction angle position of the C{002} crystal plane through XRD powder diffraction, and obtain the interlayer spacing d of the {002} crystal plane of the carbon material from the Bragg equation (Bragg diffraction formula) 2d 002 sinθ = λK 002 .

[0195] 5) Test method for particle shape and carbon grain shape:

[0196] Measure the appearance of carbon particles through atomic force microscopy (AFM) and high-power projection microscopy (HRTEM). 6) Test method for porosity:

[0197] The test method for porosity refers to GB / T 21650-2008, and it can be conveniently measured with a mercury intrusion porosimeter.

[0198] 7) Test method for powder contact angle:

[0199] Put the powder into the powder-filled groove and compact it, and test the contact angle of the carbon powder material through a contact angle tester.

[0200] 8) Test method for oil absorption value:

[0201] Drop linseed oil on the unmodified carbon material and the modified carbon material powder at a constant speed, and use a rotating wing to stir the powder. The increase in the amount of linseed oil will cause an increase in the viscosity of the mixture. The oil absorption value is the amount of linseed oil added to the carbon material powder when the torque generated by the viscosity change reaches 70% of the maximum torque.

[0202] 9) Test method for electrical conductivity of material powder:

[0203] Using a resistivity tester (Suzhou Crystal Electron ST-2255A), take 5 g of powder sample, press it under constant pressure to 5000 kg ± 2 kg with an electronic press for 15 - 25 s, place the sample between the electrodes of the tester, with the sample height h (cm), voltage U at both ends, current I, and resistance R (KΩ). The area S of the powder compacted tablet is 3.14 cm 2 , and the powder conductivity is calculated according to the formula δ = h / (S*R) / 1000, with the unit of S / m.

[0204] 10) Test method for battery performance

[0205] Test the performance of the single cell with a gas diffusion layer prepared from carbon material through a battery test bench. The anode catalyst loading of the membrane electrode used is 0.1 mg·cm -2 , and the cathode catalyst loading is 0.4 mg·cm -2 . The battery operating temperature is 80 °C, the humidity is 100 RH%, and the battery back pressure is 150 kPa / 150 kPa. Record the battery voltage at a current density of 2 A / cm 2 .

[0206] 11) Method for battery internal resistance

[0207] At a current density of 2 A / cm 2 and an AC signal of 5 kHz, test the internal resistance of the single cell through the high-frequency impedance test of an electrochemical impedance analyzer; the results of the above performance tests are as follows:

[0208]

[0209] According to the test data of Examples 1 - 6, for the carbon materials prepared by the above method, when the grain boundary density between the carbon grains on the surface of the carbon material particles decreases, the number of easily corroded sites on the carbon particle surface is less, which can effectively improve the service life of the carbon material; when the surface grain boundary density of the carbon particles is smaller, the hydrophobicity is better, and the water generated by the reaction is not easily accumulated in the pores of the carbon material, which is beneficial to maintaining the gas conduction ability of the pore structure of the microporous layer composed of this material and improving the battery performance under the conditions of high humidity and high current density. And the carbon material has both high electrical conductivity and high graphitization degree. The better the electrical conductivity performance of the same type of carbon material, the stronger the electron transport performance of the carbon material, the smaller the battery internal resistance, and the lower the power loss; when the σ / d 002 ≥3*10 8 S / cm 2 (0.338 nm ≤ d 002 ≤ 0.345 nm), the battery made of it has a current density of 2 A / cm 2The operating voltage at a current density is higher than 0.57 V, which is more than 30 mV better than that of other carbon materials, and the corresponding battery output power is also greater; the higher the graphitization degree of the carbon material, the higher the corrosion resistance of the material. As a result, the gas diffusion layer made of this material has high electrochemical conversion efficiency at high current density and has the characteristics of long service life.

[0210] According to Figure 3 As shown, from the thermogravimetric diagrams of the carbon materials of Example 1, Example 3 and Comparative Example 1, the carbon material of Comparative Example 1 undergoes rapid thermal decomposition in the range of 600 °C to 700 °C, and its thermal stability is significantly lower than that of Example 1 or Example 3.

[0211] According to Figure 4 As shown, from the electrochemical potentiodynamic polarization curves of the carbon materials of Example 1, Example 3 and Comparative Example 1 for coating to prepare fuel cell gas diffusion layers, the anti-electrochemical corrosion ability of the carbon materials is tested by simulating the reverse electrode state of the fuel cell. At a voltage of 2 V (vs RHE), the electrochemical stability of the gas diffusion layers respectively prepared by coating with the carbon materials of Example 1, Example 3 and Comparative Example 1 as the microporous layer carbon is tested by potentiodynamic polarization. From Figure 4 The test results in it can be seen that Examples 1 and 3 after high-temperature treatment show significantly higher electrochemical stability than Comparative Example 1.

[0212] Compared with Example 3, in Example 7, the content of the defect repair agent added is too small, the defects on the surface of the carbon particles are not repaired enough, and the grain boundary density of the carbon particles has increased significantly compared with Example 3, indicating that an appropriate amount of defect repair agent can fully repair the defects on the surface of the carbon particles and make carbon particles with a smaller grain boundary density.

[0213] Compared with Example 3, in Example 8, the particle size of the defect repair agent added is too small, the defects on the surface of the carbon particles cannot be effectively repaired, and the grain boundary density of the carbon particles has increased significantly compared with Example 3, indicating that using an appropriate particle size of the defect repair agent can effectively repair the defects on the surface of the carbon particles and prepare carbon particles with a smaller grain boundary density. Comparative Examples 1 to 2 are commonly used microporous layer carbon materials at present and show good performance in fuel cells. However, the carbon black material has a large p value of grain boundary density and many corrosion sites. During the long-term operation of the battery, due to reverse polarization and working environments prone to carbon corrosion such as acidic high oxygen, the carbon black material will undergo rapid deterioration and the overall service life is short.

[0214] The difference between Comparative Example 3 and Example 3 is that in Comparative Example 3, no defect repair agent is added, the surface of the carbon black material cannot be fully deposited to form a stacked carbon layer, and the grain boundary density on the surface of the carbon particles has increased significantly compared with Example 3. After the battery operates for a long time, carbon corrosion is likely to occur and the battery service life decreases.

[0215] Comparative Example 4 uses multi-walled carbon nanotubes with a length of 15 μm and a diameter of 15 nm as the carbon material. The multi-walled carbon nanotubes have a higher electrical conductivity and corrosion resistance than carbon black. The gas diffusion layer prepared by coating with this nano-carbon material is prone to form a tube cluster stacking structure, resulting in uneven coating. As a result, the battery performance assembled with this gas diffusion layer has high electron transport performance at low current densities; however, as the current density increases, the mass transfer performance of the battery decreases.

[0216] Comparative Example 5 selects single-layer ordered graphene. The single-layer graphene has a well-crystallized two-dimensional planar structure, high corrosion resistance, and high electron transport performance. However, due to its sheet structure, the stacked sheets will block the pore structure of the substrate, severely restricting the water and gas transport in the reaction. The performance of the gas diffusion layer prepared with single graphene as the microporous layer carbon material rapidly decays as the power density increases.

[0217] Comparative Example 6, compared with Example 3, does not use a modified gas to treat the carbon material. By treating the carbon material with an oxidizing gas at medium and low temperatures, the amorphous carbon deposited on the carbon surface after the volatile components in the repair agent and carbon black material are vaporized at high temperatures can be removed. The grain boundary density of the carbon grains has increased significantly compared with Example 3, the electrical conductivity has decreased significantly, and the porosity and specific surface area have decreased slightly. It shows that using an oxidizing gas can effectively remove the amorphous structure on the surface of carbon particles and prepare carbon particles with a smaller grain boundary density and higher electrical conductivity. Although this application is disclosed above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the protection scope of this application should be subject to the scope defined by the claims of this application.

Claims

1. A carbon material, characterized in that, The carbon material includes carbon particles, and the surface of the carbon particles includes a plurality of connected carbon crystallites, and grain boundaries are formed between adjacent two carbon crystallites; The grain boundary density on the surface of the carbon particles is p, and 1 ≤ p ≤ 15; Wherein, the grain boundary density is obtained by the following test method: Randomly obtain 20 carbon powder particles, and through Raman spectroscopy test, measure the peak area I of the carbon characteristic peak of the carbon powder particles D and the peak area I of the graphite characteristic peak G The ratio I D / I G is R n , n = 1, 2, 3…20; The I of 20 carbon powder particles D / I G The average value is R; Grain boundary density D is the average particle size of the carbon particles; the powder conductivity of the carbon material under a pressure of 2.5 kN / cm 2 is σ S / m, and σ ≥ 8.

4.

2. The carbon material according to claim 1, wherein The carbon material has at least one of the following characteristics: (1) The carbon particles are spherical or quasi-spherical; (2) The average particle size of the carbon particles is D, and 20 nm ≤ D ≤ 200 nm; (3) The carbon crystallites are formed by stacking carbon layers; (4) The average particle size of the carbon crystallites is La, and 3 nm ≤ La ≤ 30 nm.

3. The carbon material according to claim 1, wherein Through X-ray powder diffraction testing, the interlayer spacing of the {002} crystal plane of the graphite phase of the carbon material was measured to be d 002 nm; The carbon material has a powder conductivity of σ S / m under a pressure of 2.5 kN / cm 2 and σ / d 002 ≥ 2×10 8 S / cm 2 .

4. The carbon material according to claim 3, wherein The interlayer spacing of the crystal plane of the graphite phase {002} of the carbon material is d 002 nm, and 0.338 ≤ d 002 ≤ 0.

345.

5. The carbon material according to any one of claims 1 to 4, characterized in that, The carbon material has at least one of the following characteristics: (1) The porosity of the carbon material is ≥ 60%; (2) The powder contact angle of the carbon material is 120° - 155°; (3) The specific surface area of the carbon material is 30 m 2 / g to 250 m 2 / g; (4) The oil absorption value of the carbon material is 100 mL / 100 g - 450 mL / 100 g; (5) The average particle size of the carbon material is 0.1 μm - 10 μm.

6. A method for preparing a carbon material according to any one of claims 1 to 5, characterized in that, It includes the following steps: Placing a mixed material containing a carbon black material and a defect repair agent at 1800 °C - 3000 °C for carbonization treatment, and then performing shaping treatment; In an atmosphere containing a modifying gas, performing surface modification treatment on the shaped treatment product to obtain the carbon material.

7. The preparation method according to claim 6, characterized in that, The method has at least one of the following characteristics: (1) The boiling point of the defect repair agent is 50 °C - 400 °C; (2) The defect repair agent includes volatile organic compounds and / or semi-volatile organic compounds; (3) The defect repair agent includes volatile organic compounds, and the volatile organic compounds include at least one of camphor, phenol, o-phthalaldehyde, m-phthalaldehyde, p-phthalaldehyde, p-benzoquinone, benzoic acid, palm alcohol, aminoquinoline, and naphthalene; (4) The defect repair agent includes semi-volatile organic compounds, and the semi-volatile organic compounds include at least one of hydroquinone, phthalic acid, m-phthalaldehyde, and anthracene; (5) Before placing the mixed material containing the carbon black material and the defect repair agent at 1800 °C - 3000 °C for carbonization treatment, the method further includes performing shaping treatment on the defect repair agent, and mixing the shaped repair agent with the carbon black material to obtain a mixed material; (6) The average particle size of the defect repair agent is 0.1 μm - 1 μm; (7) The mass ratio of the carbon black material to the defect repair agent is 10:(0.1 - 2); (8) The average particle size of the carbon black material is 20 nm - 200 nm; (9) The oil absorption value of the carbon black material is 100 mL / 100 g - 450 mL / 100 g; (10) Through Raman spectroscopy testing, the carbon black material has a carbon characteristic peak I D and a graphite characteristic peak I G , I D / I G ≤ 2.0; The powder conductivity σ of the carbon black material is ≥ 8 S / m under a pressure of 2.5 kN / cm 2 。 8. The preparation method according to claim 6 or 7, characterized in that, The method has at least one of the following characteristics: (1) The time of the carbonization treatment is 0.1 h - 3 h; (2) The heating rate of the carbonization treatment is 2 °C / min - 30 °C / min; (3) The carbonization treatment is carried out under the protection of an inert gas, and the inert gas includes at least one of argon, neon, helium, and krypton; (4) The shaping treatment includes at least one of ball milling, sand milling, roller milling, stirred milling, rolling milling, and planetary milling; (5)Before performing the surface modification treatment on the shaped treatment product, the method further includes: screening the shaped treatment product.

9. The preparation method according to claim 6, characterized in that, The method has at least one of the following features: (1)The modification gas includes at least one of carbon dioxide, air, water vapor, oxygen, nitrogen, and ammonia; (2)The atmosphere further includes an inert gas, and the inert gas includes at least one of argon, neon, helium, and krypton; (3)The volume ratio of the modification gas to the inert gas in the atmosphere is (0.5 to 10):10; (4)The temperature of the surface modification treatment is 400°C to 1700°C; (5)The heating rate of the surface modification treatment is 2°C / min to 30°C / min.

10. A fuel cell, characterized in that, The fuel cell includes a plurality of battery units having a gas diffusion layer, and the gas diffusion layer includes the carbon material according to any one of claims 1 to 5 or the carbon material prepared by the preparation method according to any one of claims 6 to 9.

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