Graphite negative electrode material, preparation method therefor, lithium ion battery and electrical device

Abstract

The present application relates to the field of materials. Provided are a graphite negative electrode material, a preparation method therefor, a lithium ion battery and an electrical device. The preparation method for the graphite negative electrode material comprises: graphitizing a coke feedstock, so as to obtain a graphite aggregate; mixing asphalt with a polymer modifier, and carrying out a first heat treatment in a protective atmosphere, so as to obtain modified asphalt, the polymer modifier comprising one or more of a styrene-butadiene-styrene block copolymer, a hydrogenated styrene-butadiene block copolymer, an ethylene-vinyl acetate copolymer, styrene butadiene rubber, a styrene-isoprene copolymer and a styrene-ethylene-butylene-styrene block copolymer; mixing the graphite aggregate with the modified asphalt, and then carrying out a second heat treatment for granulation, so as to obtain a precursor; and carrying out a third heat treatment on the precursor, and performing screening and demagnetization, so as to obtain the high-energy-density and fast-charging graphite negative electrode material. The graphite negative electrode material obtained by the method provided by the present application has high energy density and superfast-charging performance.

Description

Graphite negative electrode material and preparation method thereof, lithium-ion battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 202410197014.0 filed with the Patent Office of China on February 22, 2024, entitled “Graphite negative electrode material and preparation method thereof, lithium-ion battery and electrical equipment”. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of materials, and in particular to a graphite negative electrode material and a preparation method thereof, a lithium-ion battery and electrical equipment. Background Art

[0004] As a core component of electric vehicles, high-energy-density secondary lithium-ion batteries have garnered widespread attention and hold broad market potential. In recent years, the power performance and range of electric vehicles have rivaled those of traditional internal combustion engine vehicles. However, the high time cost of charging electric vehicles, compared to the speed of refueling, limits their application, particularly in the time-sensitive commercial vehicle sector. Therefore, solving the fast-charging problem is a crucial barrier to the development of electric vehicles and a key focus of lithium-ion battery technology research and development.

[0005] In order to improve the fast charging performance of graphite materials, scientific researchers have tried many methods, but the existing methods usually only focus on improving the rate performance of graphite negative electrode materials. While the rate performance is improved, it often brings about the sacrifice of various performance aspects such as reduced capacity, reduced first efficiency, increased specific surface area, reduced tap density and increased irreversible capacity. However, in actual industrial applications, more consideration is given to taking into account various performance indicators of the material. Therefore, the capacity, first efficiency, compaction, expansion and rate performance of the material must be taken into account. In actual applications, the challenges to material performance are very great.

[0006] Therefore, improving the fast charging performance of graphite negative electrode materials while ensuring various indicators such as material capacity, initial efficiency and cycle performance has extremely great practical significance.

[0007] Summary of the Invention

[0008] The purpose of this application is to provide a graphite negative electrode material and a preparation method thereof, a lithium-ion battery and electrical equipment to solve the above problems.

[0009] To achieve the above objectives, this application adopts the following technical solutions:

[0010] A method for preparing a graphite negative electrode material, comprising:

[0011] Graphitizing the coke raw material to obtain graphite aggregate;

[0012] Mixing asphalt with a polymer modifier and performing a first heat treatment under a protective atmosphere to obtain modified asphalt; the polymer modifier includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene rubber, styrene-isoprene copolymer, and styrene-ethylene-butylene-styrene block copolymer;

[0013] The graphite aggregate and the modified asphalt are mixed, and then subjected to a second heat treatment and granulation to obtain a precursor;

[0014] The precursor is subjected to a third heat treatment, sieving, and demagnetization to obtain the graphite negative electrode material.

[0015] Preferably, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0016] (1) The coke raw material includes one or more of oil-based needle coke, coal-based needle coke, medium- and high-sulfur petroleum coke, and graphite particles;

[0017] (2) The particle size of the coke raw material meets the following requirements: Dv10 is 4-7 μm, Dv50 is 9-11 μm, and Dv90 is 19-24 μm.

[0018] Preferably, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0019] A. The graphitization temperature is 3000-3200°C and the time is 10-20h;

[0020] B. The graphitization endpoint degree g of the graphitization is 92-98%;

[0021] C. The particle size of the graphite aggregate meets the following requirements: Dv10 is 3-6 μm, Dv50 is 8.5-10 μm, and Dv90 is 18-22 μm.

[0022] Preferably, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0023] a. The particle size Dv50 of the asphalt is 1-5 μm;

[0024] b. The particle size Dv50 of the polymer modifier is 1-5 μm;

[0025] c. The mass ratio of the asphalt to the polymer modifier is 100:(1-20);

[0026] d. The particle size Dv50 of the modified asphalt is 1-5 μm;

[0027] e. The mixing time of the asphalt and the polymer modifier is 1-3h;

[0028] f. The protective atmosphere comprises nitrogen at a flow rate of 0.5-10 L / min;

[0029] g. The temperature of the first heat treatment is 150-200°C, the heating rate is 1-10°C / min, and the holding time is 1-6h.

[0030] Preferably, the molar ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer is (10-50):(90-50), the molar ratio of hydrogenated styrene to butadiene in the hydrogenated styrene-butadiene block copolymer is (10-50):(90-50), the molar ratio of ethylene to vinyl acetate in the ethylene-vinyl acetate copolymer is (10-50):(90-50), the molar ratio of styrene to 1,3-butadiene in the styrene-butadiene rubber is (10-50):(90-50), the molar ratio of styrene to isoprene in the styrene-isoprene copolymer is (10-50):(90-50), and the molar ratio of styrene, ethylene and butene in the styrene-ethylene-butylene-styrene block copolymer is (10-50):(10-30):(80-20).

[0031] Preferably, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0032] (1) The mass ratio of the graphite aggregate to the modified asphalt is 100:(1-10);

[0033] (2) The mixing time of the graphite aggregate and the modified asphalt is 1-3 hours;

[0034] (3) The second heat treatment includes a first constant temperature section and a second constant temperature section, wherein the temperature of the first constant temperature section is 250-350°C, and the temperature of the second constant temperature section is 550-600°C; and the holding time of each section is independently 1-4 hours;

[0035] (4) The heating rate of the second heat treatment is 0.2-10°C;

[0036] (5) nitrogen gas is introduced during the second heat treatment at a flow rate of 2-10 mL / min;

[0037] (6) The particle size of the precursor satisfies: Dv10 is 6-9 μm, Dv50 is 12.5-14.5 μm, and Dv90 is 22-27 μm.

[0038] Preferably, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0039] (1) The terminal temperature of the third heat treatment is 1000-1300°C, the heating rate is 0.2-10°C / min, and the holding time is 10-24h;

[0040] (2) nitrogen gas is introduced during the third heat treatment at a flow rate of 10-50 mL / min;

[0041] (3) The particle size of the graphite negative electrode material meets the following requirements: Dv10 is 6-8 μm, Dv50 is 12.5-14 μm, and Dv90 is 22-25 μm.

[0042] The present application also provides a graphite negative electrode material, which is prepared using the preparation method of the graphite negative electrode material.

[0043] The present application also provides a lithium-ion battery comprising the aforementioned graphite negative electrode material.

[0044] The present application also provides an electrical device, including the lithium-ion battery.

[0045] Compared with the prior art, the advantages of this application include:

[0046] The preparation method of the graphite negative electrode material provided by the present application, the polymer modifier adsorbs the light components in the asphalt and undergoes a swelling reaction, and at the same time, through the combined action of physical adsorption and chemical adsorption, adsorbs the saturated components and aromatic components to generate a new colloidal structure. The adsorption reaction destroys the internal fusion state of the asphalt, and obtains a three-dimensional network organic structure cross-linked with each other, while reducing the small molecules (saturated and aromatic) of the asphalt, and relatively increasing the content of polar components (colloid and asphaltene), and enhancing the interaction between asphalt molecules. Therefore, after the asphalt is modified, the density of the coated graphite can be improved, the defects on the surface of the coating layer can be reduced, and the first effect and cycle performance of the material can be improved. In addition, different polymer modifiers have different catalytic strengths for the swelling reaction. By changing the type of modifier, the components of the asphalt and the density of the asphalt coating layer after carbonization can be changed, thereby improving the fast charging and cycle performance of the asphalt, and the obtained graphite negative electrode material has high energy density and super fast charging performance.

[0047] The graphite negative electrode material provided in this application has good fast charging performance and can effectively guarantee various indicators such as material capacity, initial efficiency and cycle performance.

[0048] The lithium-ion batteries and electrical equipment provided in this application have excellent electrical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0050] FIG1 is a SEM image of the carbonized product of modified asphalt A obtained in Example 1;

[0051] FIG2 is a SEM image of the carbonized product of modified asphalt B obtained in Example 2;

[0052] FIG3 is a SEM image of the carbonized product of modified pitch C obtained in Example 3;

[0053] FIG4 is a SEM image of the carbonized product of modified asphalt D obtained in Example 4;

[0054] FIG5 is a SEM image of the carbonized product of modified asphalt E obtained in Example 5;

[0055] FIG6 is a SEM image of the carbonized product of modified asphalt F obtained in Example 6;

[0056] FIG7 is a SEM image of the carbonized product of modified asphalt G obtained in Example 7;

[0057] FIG8 is a SEM image of the carbonized pitch obtained in Comparative Example 1;

[0058] FIG9 is a SEM image of the carbonized modified asphalt H obtained in Comparative Example 2;

[0059] FIG10 is a SEM image of the carbonized product of modified asphalt I obtained in Comparative Example 3;

[0060] Figure 11 shows the pore size distribution of pitch after carbonization in different examples;

[0061] FIG12 is a diagram showing the pore size distribution of graphite negative electrode products in different examples;

[0062] FIG13 is a SEM image of the graphite negative electrode product prepared in Comparative Example 1;

[0063] FIG14 is a SEM image of the graphite negative electrode product prepared in Example 1. DETAILED DESCRIPTION

[0064] In order to better illustrate the technical solution provided by this application, before the embodiments, an overall description of the technical solution is first given, as follows:

[0065] A method for preparing a graphite negative electrode material, comprising:

[0066] Graphitizing the coke raw material to obtain graphite aggregate;

[0067] Mixing asphalt with a polymer modifier and performing a first heat treatment under a protective atmosphere to obtain modified asphalt; the polymer modifier includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene rubber, styrene-isoprene copolymer, and styrene-ethylene-butylene-styrene block copolymer;

[0068] The graphite aggregate and the modified asphalt are mixed, and then subjected to a second heat treatment and granulation to obtain a precursor;

[0069] The precursor is subjected to a third heat treatment, sieving, and demagnetization to obtain the graphite negative electrode material.

[0070] In an optional embodiment, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0071] (1) The coke raw material includes one or more of oil-based needle coke, coal-based needle coke, medium- and high-sulfur petroleum coke, and graphite particles;

[0072] (2) The particle size of the coke raw material meets the following requirements: Dv10 is 4-7 μm, Dv50 is 9-11 μm, and Dv90 is 19-24 μm.

[0073] The Dv10 of the coke raw material can be 4μm, 5μm, 6μm, 7μm or any value between 4-7μm, Dv50 can be 9μm, 10μm, 11μm or any value between 9-11μm, and Dv90 can be 19μm, 20μm, 21μm, 22μm, 23μm, 24μm or any value between 19-24μm.

[0074] In an optional embodiment, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0075] A. The graphitization temperature is 3000-3200°C and the time is 10-20h;

[0076] Optionally, the graphitization temperature may be 3000° C., 3050° C., 3100° C., 3150° C., 3200° C., or any value between 3000-3200° C., and the time may be 10 h, 15 h, 20 h, or any value between 10-20 h.

[0077] B. The graphitization endpoint degree g of the graphitization is 92-98%;

[0078] Optionally, the graphitization endpoint degree g of the graphitization may be 92%, 93%, 94%, 95%, 96%, 97%, 98% or any value between 92% and 98%;

[0079] C. The particle size of the graphite aggregate meets the following requirements: Dv10 is 3-6 μm, Dv50 is 8.5-10 μm, and Dv90 is 18-22 μm.

[0080] Optionally, the particle size Dv10 of the graphite aggregate can be 3μm, 4μm, 5μm, 6μm or any value between 3-6μm, Dv50 can be 8.5μm, 9μm, 9.5μm, 10μm or any value between 8.5-10μm, and Dv90 can be 18μm, 19μm, 20μm, 21μm, 22μm or any value between 18-22μm.

[0081] In an optional embodiment, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0082] a. The particle size Dv50 of the asphalt is 1-5 μm;

[0083] Optionally, the particle size Dv50 of the asphalt may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value between 1 and 5 μm;

[0084] b. The particle size Dv50 of the polymer modifier is 1-5 μm;

[0085] Optionally, the particle size Dv50 of the polymer modifier may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value between 1 and 5 μm;

[0086] c. The mass ratio of the asphalt to the polymer modifier is 100:(1-20);

[0087] Optionally, the mass ratio of the asphalt to the polymer modifier may be 100:1, 100:5, 100:10, 100:20 or any value between 100:(1-20);

[0088] d. The particle size Dv50 of the modified asphalt is 1-5 μm;

[0089] Optionally, the particle size Dv50 of the modified asphalt can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value between 1-5 μm;

[0090] e. The mixing time of the asphalt and the polymer modifier is 1-3h;

[0091] Optionally, the mixing time of the asphalt and the polymer modifier can be 1 h, 2 h, 3 h or any value between 1 and 3 h;

[0092] f. The protective atmosphere comprises nitrogen at a flow rate of 0.5-10 L / min;

[0093] Optionally, the flow rate of the nitrogen gas may be 0.5 L / min, 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min or any value between 0.5 and 10 L / min;

[0094] g. The temperature of the first heat treatment is 150-200°C, the heating rate is 1-10°C / min, and the holding time is 1-6h.

[0095] Optionally, the temperature of the first heat treatment can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or any value between 150-200℃, the heating rate can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any value between 1-10℃ / min, and the holding time can be 1h, 2h, 3h, 4h, 5h, 6h or any value between 1-6h.

[0096] In an optional embodiment, the molar ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer is (10-50):(90-50), the molar ratio of hydrogenated styrene to butadiene in the hydrogenated styrene-butadiene block copolymer is (10-50):(90-50), the molar ratio of ethylene to vinyl acetate in the ethylene-vinyl acetate copolymer is (10-50):(90-50), the molar ratio of styrene to 1,3-butadiene in the styrene-butadiene rubber is (10-50):(90-50), the molar ratio of styrene to isoprene in the styrene-isoprene copolymer is (10-50):(90-50), and the molar ratio of styrene, ethylene and butene in the styrene-ethylene-butylene-styrene block copolymer is (10-50):(10-30):(80-20).

[0097] Optionally, the molar ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer may be 10:90, 20:80, 30:70, 40:60, 50:50 or any value between (10-50): (90-50), the molar ratio of hydrogenated styrene to butadiene in the hydrogenated styrene-butadiene block copolymer may be 10:90, 20:80, 30:70, 40:60, 50:50 or any value between (10-50): (90-50), the molar ratio of ethylene to vinyl acetate in the ethylene-vinyl acetate copolymer may be 10:90, 20:80, 30:70, 40:60, 50:50 or any value between (10-50): (90-50), the The molar ratio of styrene to 1,3-butadiene in the styrene-butadiene rubber may be 10:90, 20:80, 30:70, 40:60, 50:50, or any value between (10-50):(90-50); the molar ratio of styrene to isoprene in the styrene-isoprene copolymer may be 10:90, 20:80, 30:70, 40:60, 50:50, or any value between (10-50):(90-50); and the molar ratio of styrene, ethylene, and butene in the styrene-ethylene-butylene-styrene block copolymer may be 10:10, 80, 20:20:60, 30:30:40, 50:30:20, or any value between (10-50):(10-30):(80-20).

[0098] In an optional embodiment, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0099] (1) The mass ratio of the graphite aggregate to the modified asphalt is 100:(1-10);

[0100] Optionally, the mass ratio of the graphite aggregate to the modified asphalt can be 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10 or any value between 100:(1-10);

[0101] (2) The mixing time of the graphite aggregate and the modified asphalt is 1-3 hours;

[0102] Optionally, the mixing time of the graphite aggregate and the modified asphalt can be 1 h, 2 h, 3 h or any value between 1 and 3 h;

[0103] (3) The second heat treatment includes a first constant temperature section and a second constant temperature section, wherein the temperature of the first constant temperature section is 250-350°C, and the temperature of the second constant temperature section is 550-600°C; and the holding time of each section is independently 1-4 hours;

[0104] Optionally, the temperature of the first constant temperature section may be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C or any value between 250-350°C; the temperature of the second constant temperature section may be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C or any value between 550-600°C; the holding time may be 1h, 2h, 3h, 4h or any value between 1-4h for each independent holding time;

[0105] (4) The heating rate of the second heat treatment is 0.2-10°C;

[0106] Optionally, the heating rate of the second heat treatment may be 0.2°C, 0.5°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C or any value between 0.2-10°C;

[0107] (5) nitrogen gas is introduced during the second heat treatment at a flow rate of 2-10 mL / min;

[0108] Optionally, the flow rate of nitrogen can be 2 mL / min, 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, or any value between 2 and 10 mL / min;

[0109] (6) The particle size of the precursor satisfies: Dv10 is 6-9 μm, Dv50 is 12.5-14.5 μm, and Dv90 is 22-27 μm.

[0110] Optionally, the particle size Dv10 of the precursor can be 6μm, 7μm, 8μm, 9μm or any value between 6-9μm, Dv50 can be 12.5μm, 13.0μm, 13.5μm, 14.0μm, 14.5μm or any value between 12.5-14.5μm, and Dv90 can be 22μm, 23μm, 24μm, 25μm, 26μm, 27μm or any value between 22-27μm.

[0111] In an optional embodiment, the method for preparing the graphite negative electrode material satisfies one or more of the following conditions:

[0112] (1) The terminal temperature of the third heat treatment is 1000-1300°C, the heating rate is 0.2-10°C / min, and the holding time is 10-24h;

[0113] Optionally, the endpoint temperature of the third heat treatment may be 1000° C., 1100° C., 1200° C., 1300° C., or any value between 1000-1300° C.; the heating rate may be 0.2° C. / min, 2° C. / min, 4° C. / min, 6° C. / min, 8° C. / min, 10° C. / min, or any value between 0.2-10° C. / min; and the holding time may be 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any value between 10-24 h.

[0114] (2) nitrogen gas is introduced during the third heat treatment at a flow rate of 10-50 mL / min;

[0115] Optionally, nitrogen is introduced during the third heat treatment, and the flow rate of the nitrogen can be 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, or any value between 10 and 50 mL / min;

[0116] (3) The particle size of the graphite negative electrode material meets the following requirements: Dv10 is 6-8 μm, Dv50 is 12.5-14 μm, and Dv90 is 22-25 μm.

[0117] Optionally, the particle size Dv10 of the graphite negative electrode material can be 6μm, 7μm, 8μm or any value between 6-8μm, Dv50 can be 12.5μm, 13.0μm, 13.5μm, 14.0μm or any value between 12.5-14μm, and Dv90 can be 22μm, 23μm, 24μm, 25μm or any value between 22-25μm.

[0118] The present application also provides a graphite negative electrode material, which is prepared using the preparation method of the graphite negative electrode material.

[0119] The present application also provides a lithium-ion battery comprising the aforementioned graphite negative electrode material.

[0120] The present application also provides an electrical device, including the lithium-ion battery.

[0121] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0122] Example 1

[0123] This embodiment provides a graphite negative electrode material with high energy density and fast charging performance, and the preparation method thereof is as follows:

[0124] Step 1: In a pulverizing device, the calcined needle coke is pulverized to obtain a powder, and the particle size of the powder is controlled to be 4.0-5.0 μm for Dv10, 9-10 μm for Dv50, and 19.0-21.0 μm for Dv90; the pulverized material is shaped, and the shaped powder is evenly mixed.

[0125] Step 2: Under nitrogen protection, the mixed powder was graphitized at a temperature of 3200°C for 12 hours, with a graphitization degree g of 95.6.

[0126] Step 3: The graphitized material is sieved with a mesh size of 250 to remove the lumps that are rapidly coked at high temperature during the graphitization process to obtain graphite aggregate with a particle size of Dv10 of 4.3 μm, Dv50 of 9.1 μm, and Dv90 of 21.2 μm.

[0127] Step 4: The graphite aggregate and modified asphalt A were fully mixed in a mass ratio of 100:3 for 1 hour to make the asphalt evenly distributed in the graphite aggregate to prepare a mixture.

[0128] The preparation method of modified asphalt is as follows: asphalt (Dv50: 3~4μm) and styrene-butadiene-styrene block copolymer (the ratio of styrene to butadiene is 20:80, Dv50: 3~4μm) are mixed in a VC mixer for 1 hour, and the molar ratio of asphalt to styrene-butadiene-styrene block copolymer is 100:6. Then, the mixture is added into a high-temperature reactor, nitrogen is introduced, and the temperature is raised to 190°C at a heating rate of 2°C / min. The mixture is reacted for 1 hour (first heat treatment) to obtain modified asphalt A, whose particle size Dv50 is 4.1μm.

[0129] Step 5: The mixture is subjected to surface coating modification treatment (second heat treatment, carried out under nitrogen atmosphere, nitrogen flow rate is 2mL / min), which includes two stages, the temperature of the first stage is 325℃, the time is 2h; the temperature of the second stage is 600℃, the time is 3h; the heating rates of the two stages are 2.7℃ / min and 1.5℃ / min. The surface coating modification treatment is carried out under stirring conditions, and the stirring speed is 15rpm / min to obtain a granulated product (precursor), the precursor particle size is Dv10 of 7.6μm, Dv50 of 13.8μm, and Dv90 of 24.9μm.

[0130] Step 6: Under nitrogen protection, the granulated product was carbonized (the third heat treatment was carried out under a nitrogen atmosphere with a nitrogen flow rate of 2 mL / min), heated to 1150°C at a heating rate of 2°C / min, and kept at 1150°C for 12 hours. Finally, a screening treatment was performed for 5 hours to remove large particles after carbonization treatment to obtain a fast-charging graphite negative electrode material A with a Dv10 of 7.4 μm, a Dv50 of 13.1 μm, and a Dv90 of 24.5 μm.

[0131] Example 2

[0132] The styrene-butadiene-styrene block copolymer (the ratio of styrene to butadiene is 20:80, Dv50: 3~4μm) in step 4 of Example 1 is replaced with a styrene-butadiene-styrene block copolymer (the ratio of styrene to butadiene is 30:70, Dv50: 3~4μm) to obtain modified asphalt B. The remaining steps are the same as in Example 1.

[0133] Example 3

[0134] The styrene-butadiene-styrene block copolymer (the ratio of styrene to butadiene is 20:80, Dv50: 3~4μm) in step 4 of Example 1 is replaced with a styrene-butadiene-styrene block copolymer (the ratio of styrene to butadiene is 40:60, Dv50: 3~4μm) to obtain modified asphalt C. The remaining steps are the same as in Example 1.

[0135] Example 4

[0136] The ratio of asphalt to styrene-butadiene-styrene block copolymer in step 4 of Example 1 was changed from 100:6 to 100:4 to obtain modified asphalt D. The remaining steps were the same as in Example 1.

[0137] Example 5

[0138] The ratio of asphalt to styrene-butadiene-styrene block copolymer in step 4 of Example 1 was changed from 100:6 to 100:8 to obtain modified asphalt E. The remaining steps were the same as in Example 1.

[0139] Example 6

[0140] The temperature of 190° C. in step 4 of Example 1 was changed to 180° C. to obtain modified asphalt F. The remaining steps were the same as those in Example 1.

[0141] Example 7

[0142] The temperature in step 4 of Example 1 was changed from 190°C to 210°C to obtain modified asphalt G. The remaining steps were the same as those in Example 1.

[0143] Comparative Example 1

[0144] The modified asphalt in step 4 of Example 1 was replaced with asphalt raw material, and the remaining steps were the same as in Example 1.

[0145] Comparative Example 2

[0146] The asphalt modifier (styrene-butadiene-styrene block copolymer) in step 4 of Example 1 was replaced with styrene to prepare modified asphalt H. The remaining steps were the same as in Example 1.

[0147] Comparative Example 3

[0148] The asphalt modifier (styrene-butadiene-styrene block copolymer) in step 4 of Example 1 was replaced with butadiene to prepare modified asphalt I. The remaining steps were the same as in Example 1.

[0149] Preparation of pitch carbonized products:

[0150] The modified asphalts obtained in Examples 1-7 and Comparative Examples 2-3, and the asphalt raw material of Comparative Example 1 were carbonized according to the method of Step 6 of Example 1 to obtain corresponding asphalt carbonized products, whose morphologies are shown in Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0151] The morphology analysis of asphalt carbonized products is as follows:

[0152] 1) The SEM of the carbonized product of conventional asphalt (Comparative Example 1) shows ( FIG8 ) that the surface is rough and highly disordered, and the asphalt cannot form a dense coating during the coking process.

[0153] 2) The morphology of the carbonized modified asphalt AF products (Examples 1-6) prepared with the styrene-butadiene copolymer modifier is more regular and smooth, and the coating layer formed by this type of asphalt during the coking process is denser, indicating that the modifier has fully played its modifying role.

[0154] 3) The modified asphalt prepared in Comparative Examples 2-3 and Example 7 did not achieve the purpose of asphalt modification. After carbonization, the surface disorder was high, and the coating layer formed by this type of asphalt during the coking process was not dense enough.

[0155] Analysis shows that the modification effects of styrene and butadiene monomers are poor.

[0156] A higher modification temperature will inactivate the modifier and fail to achieve the modification purpose (Figure 7).

[0157] The pore size distribution of the carbonized pitch products obtained in the examples and comparative examples is shown in FIG11 .

[0158] The pore size distribution analysis of asphalt carbonized products is as follows:

[0159] 1) The modified asphalt carbonized products prepared in Examples 1-6 have fewer macropores and are more densely cross-linked during the carbonization process.

[0160] 2) After carbonization, the pure asphalt prepared in Example 1 has a large amount of light components, which decompose during carbonization, resulting in a high degree of surface disorder. The coating layer formed by this type of asphalt during the coking process is not dense enough.

[0161] 3) The modified asphalt prepared in Comparative Examples 2-3 and Example 7 did not achieve the purpose of asphalt modification. After carbonization, the surface disorder was high, and the coating layer formed by this type of asphalt during the coking process was not dense enough.

[0162] Analysis shows that the modification effect of styrene and butadiene monomers is poor and the content of light components is high.

[0163] A higher modification temperature will cause the modifier to be inactivated, resulting in a high content of light components and failing to achieve the modification purpose.

[0164] The pore size distribution diagrams of the negative electrode products obtained in Example 1 and Comparative Example 1 are shown in FIG12 .

[0165] The SEM analysis of the graphite negative electrode product is as follows:

[0166] As shown in Figure 13, the surface of the raw asphalt granules is rough, and the coating layer is not densely covered; the surface of the modified asphalt granules is smooth and flat, and the coating layer is densely covered (Figure 14).

[0167] The basic properties of asphalt raw materials and different modified asphalt raw materials and their carbonized products are shown in Table 1:

[0168] Table 1 Asphalt performance data

[0169] As can be seen from Table 1, by comparing Examples 1-6 with Comparative Example 1, it can be seen that the β resin content of the modified asphalt increases and the residual carbon content of the asphalt increases.

[0170] Compared with styrene or butadiene monomer modifiers, the modified asphalt obtained by styrene-butadiene-styrene block copolymer modification has higher β resin, higher softening point, smaller specific surface area and higher residual carbon.

[0171] Raman tests were performed on the modified asphalt granules of the embodiment and the comparative example, and the results are shown in Table 2 below:

[0172] Table 2 Raman results

[0173] Raman results show that the modified asphalt granulation products (Examples 1-6) have D / I G It is smaller than the comparative example product, indicating that the surface defects of the modified asphalt granules prepared in Examples 1-6 are fewer and the coating layer is denser.

[0174] Preparation method and specific testing method of button battery:

[0175] The preparation method of button batteries is as follows:

[0176] The performance of the negative electrode materials in the examples and comparative examples was verified using a half-cell test method. The ratio of graphite: CMC: SP: SBR was 95:1.5:1.5:2. An appropriate amount of water was added to form a slurry, which was then applied to copper foil. The coated electrode was then dried in a vacuum drying oven at 110°C for 4 hours before use. The electrolyte solution was 1 mol / L LiPF6 / EC / DEC / DM. A lithium metal sheet served as the counter electrode, and a polypropylene microporous membrane served as the separator. The battery was assembled.

[0177] The testing method for button batteries is as follows:

[0178] 1) Battery capacity characterization test

[0179] First, charge the battery at a constant current of 0.2C to 4.2V, then charge it at a constant voltage to a current of 10mA, and then leave it for 10 minutes. Then discharge it at a constant current of 0.2C to 2.7V, and then leave it for 10 minutes. The battery is charged and discharged three times according to this procedure to obtain the battery capacity.

[0180] 2) Rate test

[0181] The prepared button battery was cycled 10 times at 0.1C, 0.5C, 1C, 2C, and 0.1C to test the rate performance of the electrode material.

[0182] The performance indicators of the obtained negative electrode material and the prepared button battery are shown in Table 3:

[0183] Table 3 Negative electrode material indicators

[0184] Compared with the raw asphalt granulation product (Comparative Example 1), the capacity of the modified asphalt granulation product is increased by more than 4 mAh / g, and the first efficiency is higher and the rate performance is better.

[0185] Compared with the granulated products of modified asphalt prepared from styrene or butadiene monomers, the granulated products of modified asphalt prepared from styrene-butadiene copolymer modifier have higher capacity, higher first efficiency and better rate performance.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application. Industrial Applicability

[0187] The present application provides a graphite negative electrode material and a preparation method thereof, a lithium-ion battery and electrical equipment. The obtained graphite negative electrode material has good fast charging performance and can effectively guarantee various indicators such as the material's capacity, first effect and cycle performance.

[0188] In addition, it can be understood that the graphite negative electrode material and its preparation method, lithium-ion battery and electrical equipment of the present application are reproducible and can be widely used in the field of materials.

Claims

1. A method for preparing a graphite negative electrode material, characterized in that: include: Graphitizing the coke raw material to obtain graphite aggregate; Mixing asphalt with a polymer modifier and performing a first heat treatment under a protective atmosphere to obtain modified asphalt; the polymer modifier includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene rubber, styrene-isoprene copolymer, and styrene-ethylene-butylene-styrene block copolymer; The graphite aggregate and the modified asphalt are mixed, and then subjected to a second heat treatment and granulation to obtain a precursor; The precursor is subjected to a third heat treatment, sieving, and demagnetization to obtain the graphite negative electrode material.

2. The method for preparing a graphite negative electrode material according to claim 1, wherein One or more of the following conditions are met: (1) The coke raw material includes one or more of oil-based needle coke, coal-based needle coke, medium- and high-sulfur petroleum coke, and graphite particles; (2) The particle size of the coke raw material meets the following requirements: Dv10 is 4-7 μm, Dv50 is 9-11 μm, and Dv90 is 19-24 μm.

3. The method for preparing a graphite negative electrode material according to claim 1, wherein One or more of the following conditions are met: A. The graphitization temperature is 3000-3200°C and the time is 10-20h; B. The graphitization endpoint degree g of the graphitization is 92-98%; C. The particle size of the graphite aggregate meets the following requirements: Dv10 is 3-6 μm, Dv50 is 8.5-10 μm, and Dv90 is 18-22 μm.

4. The method for preparing a graphite negative electrode material according to claim 1, wherein One or more of the following conditions are met: a. The particle size Dv50 of the asphalt is 1-5 μm; b. The particle size Dv50 of the polymer modifier is 1-5 μm; c. The mass ratio of the asphalt to the polymer modifier is 100:(1-20); d. The particle size Dv50 of the modified asphalt is 1-5 μm; e. The mixing time of the asphalt and the polymer modifier is 1-3h; f. The protective atmosphere comprises nitrogen at a flow rate of 0.5-10 L / min; g. The temperature of the first heat treatment is 150-200°C, the heating rate is 1-10°C / min, and the holding time is 1-6h.

5. The method for preparing a graphite negative electrode material according to claim 1, wherein: The molar ratio of styrene to butadiene in the styrene-butadiene-styrene block copolymer is (10-50):(90-50), the molar ratio of hydrogenated styrene to butadiene in the hydrogenated styrene-butadiene block copolymer is (10-50):(90-50), the molar ratio of ethylene to vinyl acetate in the ethylene-vinyl acetate copolymer is (10-50):(90-50), the molar ratio of styrene to 1,3-butadiene in the styrene-butadiene rubber is (10-50):(90-50), the molar ratio of styrene to isoprene in the styrene-isoprene copolymer is (10-50):(90-50), and the molar ratio of styrene, ethylene and butene in the styrene-ethylene-butylene-styrene block copolymer is (10-50):(10-30):(80-20).

6. The method for preparing a graphite negative electrode material according to claim 1, wherein: One or more of the following conditions are met: (1) The mass ratio of the graphite aggregate to the modified asphalt is 100:(1-10); (2) The mixing time of the graphite aggregate and the modified asphalt is 1-3 hours; (3) The second heat treatment includes a first constant temperature section and a second constant temperature section, wherein the temperature of the first constant temperature section is 250-350°C, and the temperature of the second constant temperature section is 550-600°C; and the holding time of each section is independently 1-4 hours; (4) The heating rate of the second heat treatment is 0.2-10°C; (5) nitrogen gas is introduced during the second heat treatment at a flow rate of 2-10 mL / min; (6) The particle size of the precursor satisfies: Dv10 is 6-9 μm, Dv50 is 12.5-14.5 μm, and Dv90 is 22-27 μm.

7. The method for preparing a graphite negative electrode material according to any one of claims 1 to 6, characterized in that: One or more of the following conditions are met: (1) The terminal temperature of the third heat treatment is 1000-1300°C, the heating rate is 0.2-10°C / min, and the holding time is 10-24h; (2) nitrogen gas is introduced during the third heat treatment at a flow rate of 10-50 mL / min; (3) The particle size of the graphite negative electrode material meets the following requirements: Dv10 is 6-8 μm, Dv50 is 12.5-14 μm, and Dv90 is 22-25 μm.

8. A graphite negative electrode material, characterized in that The method for preparing the graphite negative electrode material according to any one of claims 1 to 7 is used to prepare the graphite negative electrode material.

9. A lithium-ion battery, characterized in that: Including the graphite negative electrode material according to claim 8.

10. An electrical equipment, characterized in that: Including the lithium ion battery according to claim 9.

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