Graphite composite material and its preparation method and application

Abstract

The present invention discloses a graphite composite material, its preparation method and application. The preparation method of the graphite composite material comprises the following steps: melting crushed raw coke, catalyst, graphene and binder to obtain a mixture, then hot pressing the mixture to obtain briquetted graphite; sequentially pre-carbonizing the briquetted graphite, performing low-temperature graphitization treatment and high-temperature graphitization treatment to obtain a graphite material; and heat-treating the graphite material under the condition of passing a carbon source gas containing heteroatoms to obtain a graphite composite material. The preparation method of the graphite composite material of the present invention, by doping graphene and catalyst into the raw coke, relies on the high electronic conductivity and high ductility of graphene to increase the compaction density of the material; the nanopores left by the high-temperature volatilization of the catalyst can also increase the specific surface area of ​​the material, shorten the transmission path of lithium ions during the charge and discharge process, and improve the fast charging performance of the material.

Description

Technical Field

[0001] The present invention relates to the field of secondary batteries, and in particular to a preparation method of a graphite composite material, the graphite composite material and applications thereof. Background Art

[0002] As a green and environmentally friendly new energy source, lithium-ion batteries offer advantages such as good reliability, high safety, compact size, and light weight. They are currently widely used in digital products, electric vehicles, military products, and other fields. The booming new energy industry has led to the rapid development of lithium-ion batteries, but this has also led to increasing demands for their lifespan, safety, and low cost. Currently, lithium-ion batteries are developing in the direction of longer life, higher safety, higher rate capability, and lower cost.

[0003] Anode materials are one of the key factors limiting the energy density and rate charge-discharge performance of lithium-ion batteries. Anode materials used in energy storage batteries primarily utilize highly isotropic raw materials, artificial graphite with low specific surface area and low expansion. However, as these materials expand during cycling, they form a new SEI film, which consumes lithium ions and causes a decrease in cycling performance.

[0004] Compared to natural graphite anode materials, artificial graphite anode materials have superior performance and have become the mainstream anode materials for power batteries. Currently, the raw materials used to prepare artificial graphite lithium-ion battery anode materials are mainly raw coke, including needle coke, petroleum coke, and pitch coke.

[0005] As the market demands for the energy density and fast-charging performance of lithium-ion batteries increase, the graphite negative electrode materials used in lithium-ion batteries are required to have high specific capacity, compaction density and excellent fast-charging performance. However, it is difficult for the currently commercialized graphite negative electrode materials to simultaneously improve both energy density and fast-charging performance. The reason is that the energy density of graphite is mainly improved by increasing the degree of graphitization and increasing the particle size, but this will reduce the fast-charging performance of the material. The fast-charging performance is mainly improved by reducing the particle size, amorphous carbon coating and secondary granulation, which will also reduce the specific capacity, compaction density and initial efficiency of the material. Although researchers have improved the energy density of materials by doping silicon-based materials, this results in large expansion when fully charged, and reduced cycle performance and electronic conductivity. Patent application number CN202210609143.7 discloses a method for preparing graphite negative electrode materials with high energy density and fast charging for lithium batteries. The modified graphene is evenly distributed in the graphite phase through mixing, pressing and graphitization. The two have good contact performance, which greatly enhances the electrical conductivity of the graphite material and its coating layer; secondly, catalytic graphitization can increase the capacity of graphite to more than 360mAh / g, further improving the energy density of the battery; the synergistic effect brought about by graphene modification and catalyst pore creation improves the fast charging performance, but catalytic graphitization brings about an increase in the specific surface area of ​​the material and an increase in the first efficiency, resulting in its low first efficiency. Although the internal pores of the material increase, the isotropy of the material is poor, and the fast charging performance of the material is deviated. Summary of the Invention

[0006] Based on this, it is necessary to provide a method for preparing a graphite composite material that can solve the above problems.

[0007] In addition, it is also necessary to provide a graphite composite material prepared by the preparation method of the graphite composite material and applications of the graphite composite material.

[0008] A method for preparing a graphite composite material comprises the following steps:

[0009] Melting the crushed raw coke, catalyst, graphene and binder to obtain a mixture, and then hot pressing the mixture to obtain briquetted graphite;

[0010] The graphite block is heated to 500-800°C for pre-carbonization for 1-6 hours, then heated to 2000-2500°C for low-temperature graphitization for 6 hours to 18 hours, and then heated to 3000-3200°C for high-temperature graphitization for 12 hours to 48 hours to obtain a graphite material;

[0011] The graphite material is heat-treated under the condition of introducing a carbon source gas containing heteroatoms to obtain a graphite composite material.

[0012] In one embodiment, in the operation of melting the crushed raw coke, catalyst, graphene and binder, the mass ratio of the raw coke, the catalyst, the graphene and the binder is 100:1-5:1-5:5-15.

[0013] In one embodiment, the binder is polyamide asphalt;

[0014] The polyamide asphalt is prepared by the following method: asphalt, amino acid anhydride and initiator are evenly mixed in a mass ratio of 100:1-5:0.5-2, and stirred at a temperature of 100°C-200°C and a speed of 500rpm-100rpm for 1h-4h, filtered and dried to obtain the polyamide asphalt.

[0015] In one embodiment, the amino acid anhydride is selected from at least one of 4-dimethylaminobenzoic anhydride, 3-dimethylaminobenzoic anhydride and 3-acetamidophthalic anhydride;

[0016] The initiator is selected from at least one of peracetic acid, peroxyacetic acid and perbenzoic acid.

[0017] In one embodiment, in the operation of melting the crushed raw coke, catalyst, graphene and binder, the temperature of the melting treatment is 300° C.-500° C., and the time of the melting treatment is 1 hour-6 hours;

[0018] In the operation of hot pressing the mixture, the hot pressing pressure is 20 MPa-50 MPa, the hot pressing time is 2 h-4 h, and the hot pressing temperature is 100° C.-200° C.

[0019] In one embodiment, the raw coke is selected from at least one of petroleum coke, oil-based needle coke, coal-based needle coke and pitch coke;

[0020] The catalyst is selected from at least one of nickel chloride, cupric chloride, ferric chloride, nickel powder, cobalt powder and iron powder.

[0021] In one embodiment, the graphite material is heat treated under the condition of passing a carbon source gas containing heteroatoms, the heat treatment temperature is 700°C-1000°C, the heat treatment time is 30min-300min, and the flow rate of the carbon source gas containing heteroatoms is 100ml / min-500ml / min.

[0022] In one embodiment, the carbon source gas containing heteroatoms is at least one of CF4, COF2, CH2O, C2F4H2 and CCl3F.

[0023] A graphite composite material is prepared by the above-mentioned graphite composite material preparation method.

[0024] Application of the above-mentioned graphite composite materials in the field of energy storage devices.

[0025] The preparation method of the graphite composite material of the present invention increases the compaction density of the material by doping graphene into the raw coke, relying on the high electronic conductivity and high ductility of graphene; at the same time, a catalyst is added to promote the graphitization reaction process. In addition, the nanopores left by the high-temperature volatilization of the catalyst can also increase the specific surface area of ​​the material, shorten the transmission path of lithium ions during charging and discharging, and improve the fast charging performance of the material; at the same time, a binder is doped into the material, and after the binder is carbonized, the isotropy of the material is improved, expansion is reduced, the insertion and extraction path of lithium ions during charging and discharging is shortened, and the fast charging performance of the material is improved.

[0026] In addition, the preparation method of the graphite composite material of the present invention deposits heteroatom-doped amorphous carbon on the surface of the graphite material by vapor deposition. Compared with traditional liquid phase and solid phase coating methods, it has the advantages of good coating uniformity, high electronic conductivity, and reduction of the specific surface area of ​​the core of the prepared graphite composite material, thereby improving the fast charging performance and initial efficiency of the prepared graphite composite material.

[0027] In combination with specific embodiments, the powder conductivity and OI value of the graphite composite material prepared by the preparation method of the graphite composite material of the present invention are significantly better than those of the comparative example. The discharge specific capacity, rate and cycle performance of the negative electrode sheet prepared using this graphite composite material are significantly higher than those of the comparative example. The rate charging performance of the soft-pack battery prepared using this graphite composite material is significantly better than that of the comparative example, and the charging time is shorter, indicating that the composite negative electrode material of the present invention has good fast charging performance.

[0028] Preferably, in this embodiment, the binder is polyamide pitch. Adding polyamide pitch to the raw coke can enhance the material's liquid retention and improve ion transport pathways by leveraging its good isotropy, high electronic conductivity, and the micron and nanopores generated after carbonization.

[0029] In addition, polyamide asphalt can form -OCO- structure and pores between graphite by relying on its own oxygen free radicals. Moreover, the isotropy formed after carbonization of polyamide asphalt is high, which reduces expansion, shortens the insertion and extraction path of lithium ions during charging and discharging, and improves fast charging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] in:

[0032] Figure 1 The present invention is a flow chart of a method for preparing a graphite composite material according to one embodiment.

[0033] Figure 2 This is the SEM image of the graphite composite material prepared in Example 1. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] In the present invention, the descriptions of "first," "second," etc. are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the aforementioned features. In addition, the technical solutions of the various embodiments may be combined with each other, but this must be based on the fact that they can be implemented by a person of ordinary skill in the art. If the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0036] Combine Figure 1 The present invention discloses a method for preparing a graphite composite material according to an embodiment of the present invention, comprising the following steps:

[0037] S10, melting the crushed raw coke, catalyst, graphene and binder to obtain a mixture, and then hot pressing the mixture to obtain briquetted graphite.

[0038] Graphene, as a new type of two-dimensional layered carbon material, has a high aspect ratio and excellent hydrophobicity, thermal conductivity and chemical stability. The conjugated system makes its electron conduction ability very strong and has excellent electrical conductivity.

[0039] By doping graphene into the raw coke, the compaction density of the material is improved by relying on the high electronic conductivity and high ductility of graphene.

[0040] By doping the raw coke with a binder, the isotropy of the material is improved after the binder is carbonized, the expansion is reduced, the insertion and extraction path of lithium ions during the charge and discharge process is shortened, and the fast charging performance of the material is improved.

[0041] It should be noted that in S10, the melting process needs to be performed under a protective gas atmosphere, which can be nitrogen, helium, neon, argon, etc.

[0042] Preferably, in the present embodiment, in the operation of melting the crushed raw coke, catalyst, graphene and binder, the mass ratio of the raw coke, catalyst, graphene and binder is 100:1-5:1-5:5-15.

[0043] Preferably, in this embodiment, the binder is polyamide pitch. Adding polyamide pitch to the raw coke can enhance the material's liquid retention and improve ion transport pathways by leveraging its good isotropy, high electronic conductivity, and the micron and nanopores generated after carbonization.

[0044] In addition, polyamide asphalt can form -OCO- structure and pores between graphite by relying on its own oxygen free radicals. Moreover, the isotropy formed after carbonization of polyamide asphalt is high, which reduces expansion, shortens the insertion and extraction path of lithium ions during charging and discharging, and improves fast charging performance.

[0045] Specifically, in this embodiment, polyamide asphalt can be prepared by the following method: asphalt, amino acid anhydride and initiator are evenly mixed in a mass ratio of 100:1-5:0.5-2 and stirred at a temperature of 100℃-200℃ and a speed of 500rpm-100rpm for 1h-4h, filtered and dried to obtain polyamide asphalt.

[0046] Generally, the amino acid anhydride can be selected from at least one of 4-dimethylaminobenzoic anhydride, 3-dimethylaminobenzoic anhydride and 3-acetamidophthalic anhydride.

[0047] Generally speaking, the initiator can be selected from at least one of peracetic acid, peroxyacetic acid and perbenzoic acid.

[0048] Preferably, in this embodiment, in the operation of melting the crushed raw coke, catalyst, graphene and binder, the melting temperature is 300° C.-500° C., and the melting time is 1 h-6 h.

[0049] Specifically, in this embodiment, the crushed raw coke, catalyst, graphene and binder are melt-treated to obtain a mixture. The operation can be: adding the crushed raw coke, catalyst, graphene and binder to a mechanical fusion machine, heating to 300℃-500℃ for melting treatment for 1h-6h, and naturally cooling to room temperature to obtain a mixture.

[0050] Preferably, in the present embodiment, in the operation of hot pressing the mixture, the hot pressing pressure is 20 MPa-50 MPa, the hot pressing time is 2 h-4 h, and the hot pressing temperature is 100° C.-200° C.

[0051] Specifically, in this embodiment, the operation of hot pressing the mixture to obtain the briquetted graphite may be: passing the mixture into a hot press, controlling the pressure to 20 MPa-50 MPa and maintaining the pressure for 2-4 hours to obtain the briquetted graphite.

[0052] Preferably, in this embodiment, the raw coke is selected from at least one of petroleum coke, oil-based needle coke, coal-based needle coke and pitch coke.

[0053] Petroleum coke is a black solid coke produced by cracking and coking vacuum residue of petroleum in a coking unit at 500-550°C. It is generally considered to be an amorphous carbon or a highly aromatized high-molecular carbide containing tiny graphite crystals in the form of needles or granules.

[0054] Petroleum coke can be used as a raw material for energy storage materials to prepare artificial graphite or porous carbon, thereby increasing the added value of petroleum coke.

[0055] Needle coke is a porous solid with a silvery-gray appearance and a metallic luster. It is a high-quality carbon material. Its structure features a distinct flow texture and is slightly oval in shape. The particles have a large aspect ratio, a fibrous or needle-like texture, and a smooth feel. Needle coke boasts high carbon content, low sulfur, low nitrogen, and low ash content. After graphitization, it exhibits outstanding electrochemical and mechanical properties, making it an anisotropic, easily graphitizable, high-end carbon material.

[0056] Needle coke can be divided into two types: oil-based needle coke and coal-based needle coke. Needle coke produced from petroleum residue is oil-based needle coke, while needle coke produced from coal tar pitch and its fractions is coal-based needle coke.

[0057] Pitch coke is the solid residue obtained after high-temperature dry distillation or delayed coking of coal tar pitch. Coal tar pitch is abundant, inexpensive, has a high carbon content, good fluidity, and is easily graphitized. It is one of the most important and fundamental matrix precursors in the production of various carbon materials.

[0058] Preferably, in this embodiment, the catalyst is selected from at least one of nickel chloride, cupric chloride, ferric chloride, nickel powder, cobalt powder and iron powder.

[0059] S20, heating the compressed graphite to 500-800°C for pre-carbonization for 1-6 hours, then heating it to 2000-2500°C for low-temperature graphitization treatment for 6 hours to 18 hours, and then heating it to 3000-3200°C for high-temperature graphitization treatment for 12 hours to 48 hours to obtain a graphite material.

[0060] It should be noted that in S20, the heat treatment of the graphite block needs to be performed under a protective gas atmosphere, which can be a nitrogen atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, or the like.

[0061] The addition of a catalyst in S10 can accelerate the graphitization reaction process. In addition, the nanopores left by the high-temperature volatilization of the catalyst can also increase the specific surface area of ​​the material, shorten the transmission path of lithium ions during charging and discharging, and improve the fast charging performance of the material.

[0062] Low-temperature graphitization treatment at 2000℃-2500℃ for 6h-18h, then heating to high-temperature graphitization treatment at 3000℃-3200℃; firstly, low-temperature graphitization is used to remove moisture, volatile matter and metal impurities in the material, thereby improving the structural density of the material and the orientation of its carbon, and then high-temperature graphitization is performed again to reduce defects at the edge of the material and the regularity of its carbon rearrangement. The resulting material has the advantages of high tap density, high specific capacity and high first efficiency.

[0063] S30, heat-treating the graphite material under the condition of introducing a carbon source gas containing heteroatoms to obtain a graphite composite material.

[0064] Specifically, the prepared graphite composite material includes a core of graphite material and a shell of heteroatom-doped amorphous carbon material covering the core.

[0065] It should be noted that in S30, in order to save the carbon source gas containing heteroatoms, the graphite material is heat-treated under the condition of passing the carbon source gas containing heteroatoms, and then cooled to room temperature under a protective gas atmosphere. The protective gas atmosphere can be a nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, etc.

[0066] Preferably, in this embodiment, in the operation of heat treating the graphite material under the condition of passing a carbon source gas containing heteroatoms, the heat treatment temperature is 700℃-1000℃, the heat treatment time is 30min-300min, and the flow rate of the carbon source gas containing heteroatoms is 100ml / min-500ml / min.

[0067] Preferably, in this embodiment, the carbon source gas containing heteroatoms is at least one of CF4, COF2, CH2O, C2F4H2 and CCl3F.

[0068] It should be pointed out that the carbon source gas containing heteroatoms is the same gas, and its gas decomposition temperature is constant; however, when using a mixed gas of carbon source gas and heteroatom gas, due to the different decomposition temperatures of the two gases, the doping uniformity of the heteroatoms and carbon atoms is poor, and the impedance reduction of the material is limited.

[0069] The method for preparing the graphite composite material of the present invention increases the material's compaction density by doping graphene into the raw coke, relying on graphene's high electronic conductivity and high ductility. Simultaneously, a catalyst is added to accelerate the graphitization reaction process. Furthermore, the nanopores left behind by the high-temperature volatilization of the catalyst can also increase the material's specific surface area, shorten the lithium ion transmission path during the charge and discharge process, and improve the material's fast-charging performance. Simultaneously, a binder is doped into the material. After carbonization, the binder improves the material's isotropy, reduces expansion, shortens the lithium ion insertion and extraction path during the charge and discharge process, and improves the material's fast-charging performance.

[0070] In addition, the preparation method of the graphite composite material of the present invention deposits heteroatom-doped amorphous carbon on the surface of the graphite material by vapor deposition. Compared with traditional liquid phase and solid phase coating methods, it has the advantages of good coating uniformity, high electronic conductivity, and reduction of the specific surface area of ​​the core of the prepared graphite composite material, thereby improving the fast charging performance and initial efficiency of the prepared graphite composite material.

[0071] In combination with specific embodiments, the powder conductivity and OI value of the graphite composite material prepared by the preparation method of the graphite composite material of the present invention are significantly better than those of the comparative example. The discharge specific capacity, rate and cycle performance of the negative electrode sheet prepared using this graphite composite material are significantly higher than those of the comparative example. The rate charging performance of the soft-pack battery prepared using this graphite composite material is significantly better than that of the comparative example, and the charging time is shorter, indicating that the composite negative electrode material of the present invention has good fast charging performance.

[0072] Preferably, the binder is polyamide asphalt. By doping polyamide asphalt into the raw coke, the liquid retention performance of the material and the ion transmission path can be improved by relying on the characteristics of polyamide asphalt's good isotropy, high electronic conductivity, and micron-nano pores generated after carbonization. In addition, polyamide asphalt relies on its own oxygen free radicals to form -OCO- structures between graphite and form pores, and the isotropy formed after the carbonization of polyamide asphalt is high, which reduces expansion, shortens the insertion and extraction path of lithium ions during charging and discharging, and improves fast charging performance.

[0073] The present invention also discloses a graphite composite material prepared by the above-mentioned method for preparing the graphite composite material in one embodiment.

[0074] Specifically, in this embodiment, the graphite composite material includes a core of graphite material and a shell of heteroatom-doped amorphous carbon material covering the core.

[0075] The graphite composite material prepared by the preparation method of the graphite composite material of the present invention is prepared by doping graphene into the raw coke, relying on the high electronic conductivity and high ductility of graphene to improve the compaction density of the material. At the same time, a catalyst is added to improve the graphitization reaction process. In addition, the nanopores left by the high-temperature volatilization of the catalyst can also increase the specific surface area of ​​the material and shorten the transmission path of lithium ions during the charging and discharging process, thereby improving the fast charging performance of the material. At the same time, a binder is doped in the material. After the binder is carbonized, the isotropy of the material is improved, the expansion is reduced, the insertion and extraction path of lithium ions during the charging and discharging process is shortened, and the fast charging performance of the material is improved.

[0076] In addition, the graphite composite material prepared by the preparation method of the graphite composite material of the present invention deposits heteroatom-doped amorphous carbon on the surface of the graphite material by vapor deposition. Compared with traditional liquid phase and solid phase coating methods, it has the advantages of good coating uniformity, high electronic conductivity, and reduced specific surface area of ​​the core of the prepared graphite composite material, thereby improving the fast charging performance and initial efficiency of the prepared graphite composite material.

[0077] In combination with specific embodiments, the powder conductivity and OI value of the graphite composite material prepared by the preparation method of the graphite composite material of the present invention are significantly better than those of the comparative example. The discharge specific capacity, rate and cycle performance of the negative electrode sheet prepared using this graphite composite material are significantly higher than those of the comparative example. The rate charging performance of the soft-pack battery prepared using this graphite composite material is significantly better than that of the comparative example, and the charging time is shorter, indicating that the composite negative electrode material of the present invention has good fast charging performance.

[0078] The invention also discloses the application of the graphite composite material in the field of energy storage devices.

[0079] For example, the graphite composite material can be applied in the field of secondary batteries.

[0080] Specifically, the graphite composite material can be used as a negative electrode material for lithium-ion secondary batteries.

[0081] In addition, the above-mentioned graphite composite material can also be used in fields such as supercapacitors.

[0082] The following are specific examples: In the specific examples, petroleum asphalt was purchased from Dalian Mingqiang Chemical Materials Co., Ltd., model MQ-280; coal tar was purchased from Hebei Fengtaiyuan Energy Technology Co., Ltd., model s001.

[0083] Example 1

[0084] A method for preparing a graphite composite material comprises the following steps:

[0085] 100 g of petroleum asphalt, 3 g of 4-dimethylaminobenzoic anhydride and 1 g of peracetic acid were added to a three-necked flask, mixed evenly and stirred at 150° C. and 800 rpm for 2 h, filtered, and vacuum dried at 80° C. for 24 h to obtain polyamide asphalt.

[0086] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 3 g of nickel chloride, 3 g of graphene, and 10 g of polyamide asphalt were added to the mechanical fusion machine and heated to 400 ° C for melting treatment for 3 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0087] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0088] The graphite material was transferred to a tube furnace and heated to 800°C under a nitrogen atmosphere. CF4 gas was introduced at a flow rate of 300 ml / min for 120 minutes to obtain the desired graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0089] Example 2

[0090] A method for preparing a graphite composite material comprises the following steps:

[0091] 100 g of coal tar, 1 g of 3-dimethylaminobenzoic anhydride, and 0.5 g of peroxyacetic acid were added to a three-necked flask, mixed evenly, and stirred at 100°C at a speed of 500 rpm for 4 h. The mixture was filtered and vacuum-dried at 80°C for 24 h to obtain polyamide pitch:

[0092] The needle coke was crushed into 10 μm and 100 g was taken. Then, 1 g of ferric chloride, 1 g of graphene, and 5 g of polyamide asphalt were added to the mechanical fusion machine and heated to 300 ° C for melting treatment for 6 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and pressed at a pressure of 20 MPa and a temperature of 100 ° C for 4 hours to obtain a briquetted graphite.

[0093] The compressed graphite was transferred to a graphitization furnace, heated to 500°C for pre-carbonization for 6 hours under a nitrogen atmosphere, then heated to 2000°C for low-temperature graphitization for 18 hours, then heated to 3000°C for high-temperature graphitization for 12 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0094] The graphite material was transferred to a tube furnace and heated to 700°C under a nitrogen atmosphere. COF2 gas was introduced at a flow rate of 100 ml / min for 300 minutes to obtain a graphite composite material. The prepared graphite composite material includes a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0095] Example 3

[0096] A method for preparing a graphite composite material comprises the following steps:

[0097] 100 g of petroleum asphalt, 5 g of 3-acetamidophthalic anhydride, and 2 g of perbenzoic acid were added to a three-necked flask, mixed evenly, and stirred at 200° C. at a speed of 100 rpm for 1 h, filtered, and vacuum-dried at 80° C. for 24 h to obtain polyamide asphalt;

[0098] The petroleum coke was crushed into 100g and 100g was taken. Then, 5g of copper chloride, 5g of graphene, and 15g of polyamide asphalt were added to the mechanical fusion machine and heated to 500℃ for melting treatment for 1h. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and subjected to a pressure of 50Mpa and a temperature of 200℃ for 2h and maintained at this pressure to obtain a briquetted graphite.

[0099] The compressed graphite was transferred to a graphitization furnace, heated to 800°C for pre-carbonization for 1 hour under a nitrogen atmosphere, then heated to 2500°C for low-temperature graphitization for 6 hours, then heated to 3200°C for high-temperature graphitization for 12 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0100] The graphite material was transferred to a tube furnace and heated to 1000°C under a nitrogen atmosphere. CH2O gas was introduced at a flow rate of 500 ml / min for 30 minutes to produce a graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0101] Example 4

[0102] A method for preparing a graphite composite material comprises the following steps:

[0103] 100 g of petroleum asphalt, 3 g of 4-dimethylaminobenzoic anhydride and 1 g of peracetic acid were added to a three-necked flask, mixed evenly and stirred at 150° C. and 800 rpm for 2 h, filtered, and vacuum dried at 80° C. for 24 h to obtain polyamide asphalt.

[0104] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 1 g of nickel chloride, 5 g of graphene, and 5 g of polyamide asphalt were added to the mixture and added to a mechanical fusion machine. The mixture was heated to 400 ° C for melting treatment for 3 hours and naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0105] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0106] The graphite material was transferred to a tube furnace and heated to 800°C under a nitrogen atmosphere. CF4 gas was introduced at a flow rate of 300 ml / min for 120 minutes to obtain the desired graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0107] Example 5

[0108] A method for preparing a graphite composite material comprises the following steps:

[0109] 100 g of petroleum asphalt, 3 g of 4-dimethylaminobenzoic anhydride and 1 g of peracetic acid were added to a three-necked flask, mixed evenly and stirred at 150° C. and 800 rpm for 2 h, filtered, and vacuum dried at 80° C. for 24 h to obtain polyamide asphalt.

[0110] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 5 g of nickel chloride, 1 g of graphene, and 15 g of polyamide asphalt were added to the mechanical fusion machine and heated to 400 ° C for melting treatment for 3 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0111] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0112] The graphite material was transferred to a tube furnace and heated to 800°C under a nitrogen atmosphere. CF4 gas was introduced at a flow rate of 300 ml / min for 120 minutes to obtain the desired graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0113] Comparative Example 1

[0114] Comparative Example 1 is substantially the same as Example 1, with the only difference being that the polyamide asphalt is replaced with petroleum asphalt in Comparative Example 1.

[0115] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 3 g of nickel chloride, 3 g of graphene, and 10 g of petroleum asphalt were added to the mechanical fusion machine and heated to 400 ° C for melting treatment for 3 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0116] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0117] The graphite material was transferred to a tube furnace and heated to 800°C under a nitrogen atmosphere. CF4 gas was introduced at a flow rate of 300 ml / min for 120 minutes to obtain the desired graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0118] Comparative Example 2

[0119] Comparative Example 2 is substantially the same as Example 1, except that nickel chloride and graphene are not added in Comparative Example 2.

[0120] 100 g of petroleum asphalt, 3 g of 4-dimethylaminobenzoic anhydride and 1 g of peracetic acid were added to a three-necked flask, mixed evenly and stirred at 150° C. and 800 rpm for 2 h, filtered, and vacuum dried at 80° C. for 24 h to obtain polyamide asphalt.

[0121] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 10 g of polyamide asphalt was added to the mechanical fusion machine and heated to 400 ° C for melting treatment for 3 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0122] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0123] The graphite material was transferred to a tube furnace and heated to 800°C under a nitrogen atmosphere. CF4 gas was introduced at a flow rate of 300 ml / min for 120 minutes to obtain the desired graphite composite material. The prepared graphite composite material comprises a core of graphite material and a shell of heteroatom-doped amorphous carbon material surrounding the core.

[0124] Comparative Example 3

[0125] Comparative Example 3 is substantially the same as Example 1, except that COF2 gas is not introduced into Comparative Example 3. Other aspects are the same as Example 1.

[0126] 100 g of petroleum asphalt, 3 g of 4-dimethylaminobenzoic anhydride and 1 g of peracetic acid were added to a three-necked flask, mixed evenly and stirred at 150° C. and 800 rpm for 2 h, filtered, and vacuum dried at 80° C. for 24 h to obtain polyamide asphalt.

[0127] The petroleum coke was crushed into 10 μm and 100 g was taken. Then, 3 g of nickel chloride, 3 g of graphene, and 10 g of polyamide asphalt were added to the mechanical fusion machine and heated to 400 ° C for melting treatment for 3 hours. The mixture was naturally cooled to room temperature to obtain a mixture. The obtained mixture was then added to a small hot press and hot pressed at a pressure of 30 MPa and a temperature of 150 ° C for 3 hours to obtain a briquetted graphite.

[0128] The compressed graphite was transferred to a graphitization furnace, heated to 650°C for pre-carbonization for 3 hours under a nitrogen atmosphere, then heated to 2200°C for low-temperature graphitization for 12 hours, then heated to 3000°C for high-temperature graphitization for 24 hours, and then cooled to graphite in a nitrogen atmosphere to obtain a graphite material;

[0129] The graphite material is transferred to a tube furnace and heated to 800° C. under a nitrogen atmosphere to obtain the desired graphite composite material. The prepared graphite composite material includes a core of the graphite material and a shell of an amorphous carbon material covering the core.

[0130] Test Case

[0131] (1) SEM test

[0132] The graphite composite material prepared in Example 1 was subjected to SEM testing, and the results were as follows: Figure 2 shown.

[0133] Depend on Figure 2 It can be seen that the obtained composite material presents a granular structure with slight adhesion and a small amount of microporous structure on the surface. The particle size is between 10μm and 15μm, and the size distribution is uniform.

[0134] (2) Button battery test

[0135] The graphite composite materials prepared in Examples 1-3 and the graphite composite materials in Comparative Examples 1-3 were respectively used as negative electrode materials and assembled into button batteries according to the following methods:

[0136] A binder, conductive agent, and solvent were added to the negative electrode material and stirred to form a negative electrode slurry. The slurry was then coated onto copper foil, dried, rolled, and cut to produce negative electrode sheets. The binder was polyvinylidene fluoride, the conductive agent was SP conductive agent, and the solvent was NMP. The weight ratio of the negative electrode material, SP conductive agent, polyvinylidene fluoride, and NMP was 95:1:4:220. The battery was assembled in an argon-filled glove box using a metallic lithium sheet as the counter electrode, a polyethylene (PE) film, a polypropylene (PP) film, or a polyethylene propylene (PEP) composite film as the separator, and a LiPF6 / EC+DEC (LiPF6 concentration of 1.3 mol / L, EC:DEC volume ratio of 1:1) as the electrolyte.

[0137] The prepared button cells were installed in a Newwell CT-4008-5V10mA battery tester and charged and discharged at a 0.1C rate over a voltage range of 0.005V to 2.0V. The initial discharge capacity and initial discharge efficiency were measured. The 2C rate discharge capacity was tested, and the rate performance (2C / 0.1C), cycle performance (0.1C / 0.1C, 100 cycles), and initial charge DCR (50% SOC) were calculated.

[0138] The specific surface area, powder conductivity, and powder OI value of the above-mentioned negative electrode materials were tested in accordance with the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] As can be seen from Table 1, the discharge specific capacity, rate, and cycle performance of the graphite composite materials prepared in Examples 1-5 are significantly higher than those in Comparative Examples 1-3; the reason for this may be that the isotropic properties formed after carbonization of amino acid anhydride during the preparation of the graphite materials in the examples are high, which reduces expansion, shortens the insertion and extraction path of lithium ions during charge and discharge, and improves the rate performance; at the same time, heteroatom amorphous carbon is deposited on the outer layer by vapor deposition, which improves the electronic conductivity of the material, improves the powder electronic conductivity of the material, and improves the rate performance.

[0143] (3) Soft pack battery test

[0144] The graphite composite materials prepared in Examples 1-5 and the graphite composite materials in Comparative Examples 1-3 were used as negative electrode materials to prepare negative electrodes, lithium iron phosphate was used as positive electrode material to prepare positive electrodes, LiPF6 (solvent is EC+DEC, volume ratio 1:1, concentration 1.1 mol / L) was used as electrolyte, and celegard2400 was used as diaphragm to prepare 2Ah soft-pack batteries.

[0145] During negative electrode preparation, a binder, conductive agent, and solvent are added to the negative electrode material and stirred to form a negative electrode slurry. The slurry is then coated onto copper foil, dried, rolled, and cut to produce negative electrode sheets. The binder is LA132, the conductive agent is SP, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA132 binder, and double-distilled water is 95:1:4:220.

[0146] During cathode preparation, a binder, conductive agent, and solvent are added to the cathode material and stirred to form a cathode slurry. The slurry is then coated onto aluminum foil, dried, rolled, and cut to form cathode sheets. The binder is PVDF, the conductive agent is SP, and the solvent is N-methylpyrrolidone. The weight ratio of the cathode material, conductive agent, binder, and solvent is 93:3:4:140.

[0147] 1) Rate performance test

[0148] The charge and discharge voltage range is 2.8V-4.2V, the test temperature is 25±3.0℃, and the charging is performed at 1.0C, 2.0C, 5.0C, and 10.0C, and the discharge is performed at 1.0C. The constant current ratio of the battery is tested under different charging modes. The results are shown in Table 2.

[0149] Table 2

[0150] magnification 1C 2C 5C 10C Example 1 Constant current ratio (%) 96.56 91.37 82.18 63.81 Example 2 Constant current ratio (%) 95.76 90.54 80.88 60.29 Example 3 Constant current ratio (%) 97.58 93.21 84.34 67.36 Example 4 Constant current ratio (%) 97.98 93.76 85.12 69.04 Example 5 Constant current ratio (%) 95.01 89.45 79.45 65.34 Comparative Example 1 Constant current ratio (%) 90.11 83.45 68.76 51.66 Comparative Example 2 Constant current ratio (%) 92.86 85.49 72.25 55.75 Comparative Example 3 Constant current ratio (%) 92.98 86.78 74.34 59.98

[0151] From Table 2, it can be seen that the rate charging performance of the soft-pack batteries using the graphite composite materials prepared in Examples 1-5 as the negative electrode material is significantly better than that of the comparative example, and the charging time is shorter, indicating that the composite negative electrode material of the present invention has good fast charging performance. The reason may be that the graphite composite materials prepared in Examples 1-5 have high powder conductivity and low OI value, which reduces expansion and improves the fast charging performance of the graphite composite materials prepared in Examples 1-5.

[0152] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a graphite composite material, characterized in that: The steps include: Melting the crushed raw coke, catalyst, graphene and binder to obtain a mixture, and then hot pressing the mixture to obtain briquetted graphite; The graphite block is heated to 500-800°C for pre-carbonization for 1-6 hours, then heated to 2000-2500°C for low-temperature graphitization for 6 hours to 18 hours, and then heated to 3000-3200°C for high-temperature graphitization for 12 hours to 48 hours to obtain a graphite material; heat-treating the graphite material under the condition of introducing a carbon source gas containing heteroatoms to obtain a graphite composite material; In the operation of melting the crushed raw coke, catalyst, graphene and binder, the mass ratio of the raw coke, the catalyst, the graphene and the binder is 100:1-5:1-5:5-15; The binder is polyamide asphalt; The polyamide asphalt is prepared by the following method: asphalt, amino acid anhydride and initiator are evenly mixed in a mass ratio of 100:1-5:0.5-2, and stirred at a temperature of 100°C-200°C and a speed of 500rpm-100rpm for 1h-4h, filtered and dried to obtain the polyamide asphalt.

2. The method for preparing the graphite composite material according to claim 1, wherein The amino acid anhydride is selected from at least one of 4-dimethylaminobenzoic anhydride, 3-dimethylaminobenzoic anhydride and 3-acetamidophthalic anhydride; The initiator is selected from at least one of peracetic acid and perbenzoic acid.

3. The method for preparing the graphite composite material according to claim 1, wherein In the operation of melting the crushed raw coke, catalyst, graphene and binder, the temperature of the melting treatment is 300° C.-500° C., and the time of the melting treatment is 1 hour-6 hours; In the operation of hot pressing the mixture, the hot pressing pressure is 20 MPa-50 MPa, the hot pressing time is 2 h-4 h, and the hot pressing temperature is 100° C.-200° C.

4. The method for preparing the graphite composite material according to claim 1, wherein The raw coke is selected from at least one of petroleum coke and pitch coke; The catalyst is selected from at least one of nickel chloride, cupric chloride, ferric chloride, nickel powder, cobalt powder and iron powder.

5. The method for preparing a graphite composite material according to any one of claims 1 to 4, characterized in that: The graphite material is heat-treated under the condition of passing a carbon source gas containing heteroatoms, wherein the heat treatment temperature is 700°C-1000°C, the heat treatment time is 30min-300min, and the flow rate of the carbon source gas containing heteroatoms is 100ml / min-500ml / min.

6. The method for preparing the graphite composite material according to claim 5, wherein: The carbon source gas containing heteroatoms is at least one of CF4, COF2, CH2O, C2F4H2 and CCl3F.

7. A graphite composite material, characterized in that: The graphite composite material is prepared by the method for preparing the graphite composite material according to any one of claims 1 to 6.

8. Use of the graphite composite material according to claim 7 in the field of energy storage devices.

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