High-rate artificial graphite anode materials and their preparation methods, lithium-ion batteries and related electrical equipment

Abstract

This application provides a high-rate artificial graphite anode material and its preparation method, a lithium-ion battery, and related electrical equipment, relating to the field of materials. The preparation method of the high-rate artificial graphite anode material includes: mixing artificial graphite and asphalt, and then performing low-temperature granulation heat treatment under a protective atmosphere to obtain granulated material; the low-temperature granulation heat treatment includes a first heat treatment and a second heat treatment performed sequentially; and carbonizing the granulated material to obtain the high-rate artificial graphite anode material; the endpoint temperatures of the first heat treatment and the second heat treatment correspond to the metastable temperature range and viscosity abrupt change range of the rheological curve of the asphalt, respectively. The preparation method of the high-rate artificial graphite anode material provided by this application determines the heat treatment temperature through the rheological curve of the asphalt, achieving low-temperature granulation, reducing sintering and agglomeration phenomena during high-temperature processes, and lowering the difficulty and cost of subsequent processing.

Description

Technical Field

[0001] This application relates to the field of materials, and in particular to a high-rate artificial graphite anode material and its preparation method, lithium-ion batteries, and electrical equipment. Background Technology

[0002] Lithium-ion batteries, as mature green energy storage devices, have been widely used in electric vehicles, consumer electronics, base stations, and other fields, replacing some fossil fuel applications. At the same time, consumers have increasingly higher demands for lithium-ion batteries, such as fast-charging performance and cycle life. The anode material is a crucial factor affecting the cycle life and fast-charging performance of lithium-ion batteries. Typically, small-particle aggregates are used through secondary granulation to improve the rate performance of the anode material, surface modification enhances interfacial stability, and coating promotes cycle stability.

[0003] Graphite materials have the advantages of low cost and high theoretical capacity (>350mAh / g), making them a commonly used anode material for lithium batteries. However, in application, artificial graphite anodes suffer from poor rate performance and poor electrolyte compatibility, which are significant factors limiting the fast-charging performance and cycle life of lithium-ion batteries. Carbon coating on the graphite surface can effectively improve the rate performance of graphite anodes. The carbon coating method involves coating the graphite surface with a layer of amorphous carbon, forming a carbon composite material with a "core-shell" structure. Commonly used precursors for amorphous carbon materials include phenolic resin, epoxy resin, and asphalt.

[0004] Patent document CN 114068888A describes a method for preparing an anode material by carbon coating a mixture of graphite particles of varying sizes. This patent develops a graphite anode material with high specific capacity and low cost. The graphite mixture described in this patent consists of large-particle natural graphite and small-particle artificial graphite. The preparation method described in the patent includes natural graphite modification and graphitization, mixing natural graphite with artificial graphite, and coating the mixed graphite anode material with phenolic resin. However, the anode material in this patent undergoes side reactions with the electrolyte at high temperatures, leading to rapid electrolyte consumption and rapid capacity loss.

[0005] Patent document CN 104934579A introduces a method for preparing porous graphite doped and carbon-coated graphite anode materials. The improvement of graphite by porous carbon doping and carbon coating can solve the problem of poor high-rate performance of graphite. However, the method uses strong oxidants to oxidize graphite and metal compounds to dope it. On the one hand, this introduces a large number of metal impurities, and on the other hand, it poses safety hazards, increases processing costs, and makes it difficult to scale up production.

[0006] Patent document CN 112047334 A describes a method for preparing a nitrogen-doped graphite anode for lithium-ion batteries, utilizing organic reagents as a carbon source and employing a gas-solid in-situ reaction for nitrogen doping. Glucose, urea, and copper chloride are used to prepare the lithium-ion battery anode. This method shows good performance with glucose-based carbon sources, but the experimental use of large amounts of metal compounds is not conducive to cost reduction in industrial production.

[0007] In general, traditional processes for preparing graphite materials result in poor rate performance and interfacial stability, making it difficult to meet the requirements of fast charging and long lifespan for lithium-ion batteries. This paper utilizes amorphous carbon, primarily pitch, as the coating material, taking full advantage of its low cost and high carbon content to prepare graphite anode materials for lithium-ion batteries. Simultaneously, without disrupting the overall crystal structure of the graphite material, it achieves the aggregation of small graphite particles, improving the tap density and specific surface area of ​​the graphite aggregate, thus producing anode materials with good rate performance and long service life.

[0008] However, most current production lines use high temperatures to treat the asphalt and resin binders used in artificial graphite production, sintering them together with some of the graphite. While this reduces the amount of fine graphite powder and increases the particle strength, it also easily leads to sintering and agglomeration at high temperatures. This reduces the sieving rate of the carbonized product, necessitating an additional deagglomeration and crushing process, significantly increasing processing costs. Furthermore, the asphalt-based soft carbon materials themselves are prone to coking at high temperatures, failing to fully utilize their role in binding the fine graphite powder.

[0009] Current research focuses primarily on coating methods and reducing heat treatment costs. However, there is still no research on how to precisely control the granulation process to achieve both coating and granulation while avoiding coking and agglomeration. Summary of the Invention

[0010] The purpose of this application is to provide a high-rate artificial graphite anode material and its preparation method, a lithium-ion battery, and electrical equipment to solve the above-mentioned problems.

[0011] To achieve the above objectives, this application adopts the following technical solution:

[0012] A method for preparing a high-rate artificial graphite anode material includes:

[0013] Artificial graphite and asphalt are mixed, and then subjected to low-temperature granulation heat treatment under a protective atmosphere to obtain granulated material; the low-temperature granulation heat treatment includes a first heat treatment and a second heat treatment performed sequentially.

[0014] The granulated material is carbonized to obtain the high-ratio artificial graphite anode material;

[0015] The endpoint temperatures of the first heat treatment and the second heat treatment correspond to the metastable temperature range and viscosity abrupt change range of the rheological curve of the asphalt, respectively.

[0016] Preferably, the endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship:

[0017] Y = BX + k;

[0018] Where B is a calculation coefficient, ranging from 0.5 to 2.0, and is dimensionless; k is a calculation constant, ranging from 100 to 150℃.

[0019] Preferably, the endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship:

[0020] Y = X + 130℃.

[0021] Preferably, the endpoint temperature of the second heat treatment is not lower than the termination temperature at which the weight loss is complete in the thermogravimetric curve of the asphalt.

[0022] Preferably, the preparation method of high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0023] (1) The final temperature of the first heat treatment is 250-500℃, and the holding time is 1-3h;

[0024] (2) The final temperature of the second heat treatment is 500-600℃, and the holding time is 1-3h;

[0025] (3) The first heat treatment is performed by heating from room temperature to the final temperature at a heating rate of not more than 10℃ / min;

[0026] (4) The heating rate of the second heat treatment shall not exceed 10℃ / min;

[0027] (5) The protective atmosphere includes nitrogen, and the flow rate of the nitrogen is 1-10 L / min;

[0028] (6) During the low-temperature granulation heat treatment, the reaction vessel is kept under positive pressure;

[0029] (7) During the low-temperature granulation heat treatment, the material is in motion;

[0030] (8) The carbonization treatment is carried out at a temperature of 900-1200℃ for 2-6 hours.

[0031] (9) The D50 particle size of the artificial graphite is 8-11 μm, and the D50 particle size of the asphalt is not higher than 5 μm;

[0032] (10) The softening point of the asphalt is 150-380℃, and the thermal weight loss carbon content of the asphalt is between 40-70%.

[0033] (11) The asphalt includes coal-based asphalt and / or oil-based asphalt.

[0034] Preferably, the preparation method of high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0035] (1) The amount of the asphalt used is 2-8% of the total mass of the asphalt and the artificial graphite;

[0036] (2) The mixing time shall not be less than 1 hour.

[0037] This application also provides a high-rate artificial graphite anode material, which is prepared using the aforementioned method for preparing high-rate artificial graphite anode materials.

[0038] Preferably, the high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0039] (1) The high-rate artificial graphite anode material has a D10 of 5-7 μm, a D50 of 11-16 μm, and a D90 of 20-25 μm;

[0040] (2) The tap density of the high-ratio artificial graphite anode material is 0.8-1.1 g / cm³. 3 ;

[0041] (3) The specific surface area of ​​the high-ratio artificial graphite anode material is 0.9-1.3 m². 2 / g.

[0042] This application also provides a lithium-ion battery, including the aforementioned high-rate artificial graphite anode material.

[0043] This application also provides an electrical device, including the aforementioned lithium-ion battery.

[0044] Compared with the prior art, the beneficial effects of this application include:

[0045] The method for preparing high-ratio artificial graphite anode materials provided in this application uses asphalt and artificial graphite as raw materials. By measuring the rheological curve of the asphalt, the metastable temperature range and viscosity abrupt change range are obtained, thereby accurately determining the endpoint temperatures of the first and second heat treatments in the low-temperature granulation heat treatment process. This allows the high-temperature fluidity of the asphalt itself to bind the graphite powder at a lower temperature, reducing sintering and agglomeration during the high-temperature process. This achieves the purpose of coating and granulation while avoiding coking and agglomeration, reducing the difficulty and cost of subsequent processing. Simultaneously, by utilizing the characteristic of the thermal decomposition and release of low-molecular-weight volatiles in asphalt, the method maintains the temperature range (first heat treatment) where these volatiles are fully released to optimize the asphalt composition, remove low-molecular-weight impurities such as volatiles, resulting in a relatively increased amount of asphaltene and enhanced intermolecular interactions. The carbonized asphalt coating layer has superior density, reducing surface defects and thus improving the electrochemical performance of the material. Moreover, this method achieves precise temperature control through rheological curve determination, and can be applied to asphalt with different softening points. It can fully utilize the high-temperature fluidity of asphalt with different softening points, reducing the requirements for raw material selection. At the same time, by precisely controlling the temperature, particle size control after granulation is achieved, reducing the mutual adhesion and agglomeration between graphite materials after carbonization, reducing the difficulty and cost of subsequent processing of carbonized materials, and improving material performance.

[0046] The high-rate artificial graphite anode material, lithium-ion battery, and electrical equipment provided in this application exhibit excellent electrical performance. In coin cell battery testing, the initial discharge capacity is ≥355mAh / g, the initial discharge efficiency is ≥93%, the 1C discharge capacity retention rate is ≥60%, and the 2C discharge capacity retention rate is ≥26%. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0048] Figure 1 The rheological curves of the asphalt raw materials used in Examples 1 and 2 are shown.

[0049] Figure 2 The thermogravimetric curves of the asphalt raw materials used in Examples 1 and 2 are shown. Detailed Implementation

[0050] To better illustrate the technical solution provided in this application, the technical solution will be described in its entirety before the embodiments, as follows:

[0051] A method for preparing a high-rate artificial graphite anode material includes:

[0052] Artificial graphite and asphalt are mixed, and then subjected to low-temperature granulation heat treatment under a protective atmosphere to obtain granulated material; the low-temperature granulation heat treatment includes a first heat treatment and a second heat treatment performed sequentially.

[0053] The granulated material is carbonized to obtain the high-ratio artificial graphite anode material;

[0054] The endpoint temperatures of the first heat treatment and the second heat treatment correspond to the metastable temperature range and viscosity abrupt change range of the rheological curve of the asphalt, respectively.

[0055] Currently, most existing artificial graphite production lines treat the asphalt and resin binders at high temperatures to sinter them with some of the graphite. While this reduces some of the graphite powder and increases the particle strength, it also easily leads to sintering and agglomeration at high temperatures. This reduces the sieving rate of the carbonized product, necessitating an additional deagglomeration and crushing process, significantly increasing processing costs. Furthermore, soft carbon materials like asphalt are prone to coking at high temperatures, failing to fully utilize their role in binding the graphite powder.

[0056] Therefore, this application adopts a low-temperature granulation method, which is beneficial to the high-temperature fluidity of the asphalt itself to bind the graphite powder. Moreover, the low-temperature granulation process is applicable to asphalt with different softening points. This approach can also reduce the sintering and agglomeration phenomenon during the high-temperature process, thereby reducing the difficulty and cost of subsequent processing.

[0057] In the asphalt rheological curve, as the temperature rises, its viscosity decreases rapidly and then reaches a metastable state with stable viscosity. The interval corresponding to this temperature range is named the metastable temperature range. After exceeding this temperature range, the asphalt will coke, and its composition, structure and viscosity will change. Then the viscosity will stabilize again. The interval corresponding to this temperature range is named the viscosity abrupt change range.

[0058] In an optional implementation, the endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship:

[0059] Y = BX + k;

[0060] Where B is a calculation coefficient, ranging from 0.5 to 2.0, and is dimensionless; k is a calculation constant, ranging from 100 to 150℃.

[0061] Where B can be any value between 0.5, 1.0, 1.5, 2.0 or 0.5-2.0; k can be any value between 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 100-150℃.

[0062] In an optional implementation, the endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship:

[0063] Y = X + 130℃.

[0064] In an optional embodiment, the endpoint temperature of the second heat treatment is not lower than the termination temperature at which complete weight loss occurs in the thermogravimetric curve of the asphalt.

[0065] Thermogravimetric analysis is used as an auxiliary method to further improve the accuracy of temperature control in heat treatment.

[0066] In one optional implementation, the method for preparing high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0067] (1) The final temperature of the first heat treatment is 250-500℃, and the holding time is 1-3h;

[0068] Optionally, the final temperature of the first heat treatment can be any value between 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ or 250-500℃, and the holding time can be any value between 1h, 2h, 3h or 1-3h.

[0069] (2) The final temperature of the second heat treatment is 500-600℃, and the holding time is 1-3h;

[0070] Optionally, the endpoint temperature of the second heat treatment can be any value between 500, 510, 520, 530, 540, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C or 500-600°C, and the holding time can be any value between 1h, 2h, 3h or 1-3h.

[0071] (3) The first heat treatment is performed by heating from room temperature to the final temperature at a heating rate of not more than 10℃ / min;

[0072] (4) The heating rate of the second heat treatment shall not exceed 10℃ / min;

[0073] (5) The protective atmosphere includes nitrogen, and the flow rate of the nitrogen is 1-10 L / min;

[0074] Optionally, the flow rate of the nitrogen gas can be any value between 1L / min, 2L / min, 3L / min, 4L / min, 5L / min, 6L / min, 7L / min, 8L / min, 9L / min, 10L / min or 1-10L / min.

[0075] (6) During the low-temperature granulation heat treatment, the reaction vessel is kept under positive pressure;

[0076] (7) During the low-temperature granulation heat treatment, the material is in motion;

[0077] (8) The carbonization treatment is carried out at a temperature of 1000-1200℃ for 2-6 hours.

[0078] Optionally, the final temperature of the carbonization treatment can be any value between 1000℃, 1100℃, 1200℃ or 900-1200℃, and the holding time can be any value between 2h, 3h, 4h, 5h, 6h or 2-6h.

[0079] In an optional embodiment, the artificial graphite has a D50 particle size of 8-11 μm, and the asphalt has a D50 particle size of no more than 5 μm.

[0080] In one optional implementation, the method for preparing high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0081] (1) The softening point of the asphalt is 150-380℃, and the thermal weight loss residual carbon rate of the asphalt is between 40-70%.

[0082] Optionally, the softening point of the asphalt can be any value between 150℃, 200℃, 250℃, 300℃, 350℃, 380℃ or 150-380℃, and the thermal weight loss carbon residue of the asphalt can be any value between 40%, 50%, 60%, 70% or 40-70%.

[0083] (2) The asphalt includes coal-based asphalt and / or oil-based asphalt.

[0084] In one optional implementation, the method for preparing high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0085] (1) The amount of the asphalt used is 2-8% of the total mass of the asphalt and the artificial graphite;

[0086] Optionally, the amount of asphalt used can be any value between 2%, 3%, 4%, 5%, 6%, 7%, 8% or 2-8% of the total mass of the asphalt and the artificial graphite;

[0087] (2) The mixing time shall not be less than 1 hour.

[0088] This application also provides a high-rate artificial graphite anode material, which is prepared using the aforementioned method for preparing high-rate artificial graphite anode materials.

[0089] In one alternative implementation, the high-rate artificial graphite anode material satisfies one or more of the following conditions:

[0090] (1) The high-rate artificial graphite anode material has a D10 of 5-7 μm, a D50 of 11-16 μm, and a D90 of 20-25 μm;

[0091] (2) The tap density of the high-ratio artificial graphite anode material is 0.8-1.1 g / cm³. 3 ;

[0092] (3) The specific surface area of ​​the high-ratio artificial graphite anode material is 0.9-1.3 m². 2 / g.

[0093] This application also provides a lithium-ion battery, including the aforementioned high-rate artificial graphite anode material.

[0094] This application also provides an electrical device, including the aforementioned lithium-ion battery.

[0095] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0096] Example 1

[0097] This embodiment provides a high-rate artificial graphite anode material, the preparation method of which includes the following steps:

[0098] 1. Select asphalt powder with a particle size D50 of 3-5 μm after crushing, a residual carbon content of about 46%, and a softening point of about 180℃; select artificial graphite with a particle size D50 of 8-10 μm after crushing.

[0099] 2. Rheological properties of the above asphalt raw materials were tested under a nitrogen atmosphere. Figure 1 (250-500℃ is the metastable temperature range, 500-600℃ is the viscosity abrupt change range) and thermogravimetric analysis ( Figure 2 );

[0100] 3. The mass ratio of graphite to bitumen is 97:3; mix at room temperature using a solid-state mixer for 1 hour;

[0101] 4. Feed the uniformly mixed material into a horizontal rotary drum furnace, and after introducing high-purity nitrogen, set the temperature of the low-temperature granulation section according to the test results in step 2. The temperature process is as follows: heat from room temperature to 310℃±10℃ (calculated according to Y=X+130℃, where X=180℃, Y=310℃), hold for 2 hours, then heat to 500℃, and continue to hold for 2 hours. The nitrogen flow rate for the entire heat treatment process is 2L / min, and the heating rate is 4℃ / min.

[0102] 5. The material after low-temperature granulation is sent into a kiln for carbonization at 1100℃ for 3 hours. The nitrogen flow rate during the entire heat treatment process is 5L / min, and the heating rate is 2℃ / min.

[0103] 6. After passing the carbonized material prepared in step 5 through a 250-mesh sieve and demagnetizing it, the finished negative electrode material is obtained.

[0104] Example 2

[0105] This embodiment provides a high-rate artificial graphite anode material, the preparation method of which includes the following steps:

[0106] 1. Select asphalt powder with a particle size D50 of 3-5 μm after crushing, a residual carbon content of about 54%, and a softening point of about 250℃; select artificial graphite with a particle size D50 of 8-10 μm after crushing.

[0107] 2. Rheological properties of the above asphalt raw materials were tested under a nitrogen atmosphere. Figure 1 (350-500℃ is the metastable temperature range, 500-600℃ is the viscosity abrupt change range) and thermogravimetric analysis ( Figure 2 );

[0108] 3. The mass ratio of graphite to bitumen is 97:3; mix at room temperature using a solid-state mixer for 1 hour;

[0109] 4. Feed the uniformly mixed material into a horizontal rotary drum furnace, and after introducing high-purity nitrogen, set the temperature of the low-temperature granulation section according to the test results in step 2. The temperature process is as follows: heat from room temperature to 380℃±10℃ (calculated according to Y=X+130℃, where X=250℃, Y=380℃), hold for 2 hours, then heat to 500℃, and continue to hold for 2 hours. The nitrogen flow rate for the entire heat treatment process is 2L / min, and the heating rate is 4℃ / min.

[0110] 5. The material after low-temperature granulation is sent into a kiln for carbonization at 1100℃ for 3 hours. The nitrogen flow rate during the entire heat treatment process is 5L / min, and the heating rate is 2℃ / min.

[0111] 6. After passing the carbonized material prepared in step 5 through a 250-mesh sieve and demagnetizing it, the finished negative electrode material is obtained.

[0112] Example 3

[0113] 1. Select asphalt powder with a particle size D50 of 3-5 μm after crushing, a residual carbon content of about 62%, and a softening point of about 330℃; select artificial graphite with a particle size D50 of 8-10 μm after crushing.

[0114] 2. Rheological properties of the above asphalt raw materials were tested under a nitrogen atmosphere. Figure 1 (400-500℃ is the metastable temperature range, 500-600℃ is the viscosity abrupt change range) and thermogravimetric analysis ( Figure 2 );

[0115] 3. The mass ratio of graphite to bitumen is 97:3; mix at room temperature using a solid-state mixer for 1 hour;

[0116] 4. Feed the uniformly mixed material into a horizontal drum furnace, and after introducing high-purity nitrogen, set the temperature of the low-temperature granulation section according to the test results in step 2. The temperature process is as follows: heat from room temperature to 460℃ (calculated according to Y=X+130℃, where X=330℃, Y=460℃, Y can fluctuate up or down by 10℃), hold for 2 hours, then heat to 550℃, and continue to hold for 2 hours. The nitrogen flow rate of the entire heat treatment process is 2L / min, and the heating rate is 4℃ / min.

[0117] 5. The material after low-temperature granulation is sent into a kiln for carbonization at 1100℃ for 3 hours. The nitrogen flow rate during the entire heat treatment process is 5L / min, and the heating rate is 2℃ / min.

[0118] 6. After passing the carbonized material prepared in step 5 through a 250-mesh sieve and demagnetizing it, the finished negative electrode material is obtained.

[0119] Example 4

[0120] The difference from Example 1 is that the mass ratio of graphite to bitumen is 95:5.

[0121] Example 5

[0122] The difference from Example 1 is that the uniformly mixed material is fed into a horizontal drum furnace, and after high-purity nitrogen is introduced, the temperature of the low-temperature granulation section is set according to the test results in step 2. The temperature process is as follows: the temperature is raised from room temperature to 300℃±10℃, held for 2 hours, then raised to 600℃, and held for another 2 hours. The nitrogen flow rate is 2L / min and the heating rate is 4℃ / min throughout the heat treatment process.

[0123] Example 6

[0124] The difference from Example 1 is that the material after low-temperature granulation is sent into a kiln for carbonization at 1000°C for 3 hours.

[0125] Comparative Example 1

[0126] This comparative example provides an artificial graphite anode material, the preparation method of which is as follows:

[0127] 1. Select asphalt powder with a particle size D50 of 3-5 μm after crushing, a residual carbon content of about 46%, and a softening point of about 180℃; select artificial graphite with a particle size D50 of 8-10 μm after crushing.

[0128] 2. The mass ratio of graphite to bitumen is 97:3; mix at room temperature using a solid-state mixer for 1 hour;

[0129] 3. The uniformly mixed material is fed into a horizontal drum furnace, and high-purity nitrogen is introduced for staged heating. The temperature process is as follows: the temperature is raised from room temperature to 700℃ and held for 2 hours. The nitrogen flow rate during the entire heat treatment process is 2L / min.

[0130] 4. The material after high-temperature heat treatment is sent into a kiln for carbonization at 1100℃ for 3 hours. The nitrogen flow rate during the entire heat treatment process is 5L / min, and the heating rate is 2℃ / min.

[0131] 5. After passing the carbonized material prepared in step four through a 250-mesh sieve and demagnetizing it, the finished negative electrode material is obtained.

[0132] Comparative Example 2

[0133] The difference from Comparative Example 1 is that the softening point of the asphalt is approximately 250°C;

[0134] Comparative Example 3

[0135] The difference from Example 1 is that the material after low-temperature granulation is sent into a kiln for carbonization at 1300°C for 3 hours, and the nitrogen flow rate during the entire heat treatment process is 5L / min, and the heating rate is 2°C / min.

[0136] Comparative Example 4

[0137] The difference from Example 1 is that the mass ratio of graphite to bitumen is 90:10.

[0138] Comparative Example 5

[0139] The difference from Example 1 is that the uniformly mixed material is fed into a horizontal drum furnace, and after high-purity nitrogen is introduced, the temperature of the low-temperature granulation section is set according to the test results of step 2. The temperature process is as follows: the temperature is raised from room temperature to 200℃±10℃, held for 2 hours, then raised to 550℃, and held for another 2 hours. The nitrogen flow rate during the entire heat treatment process is 2L / min, and the heating rate is 4℃ / min.

[0140] Comparative Example 6

[0141] The difference from Example 1 is that the uniformly mixed material is fed into a horizontal drum furnace, and high-purity nitrogen is introduced to set the temperature of the granulation section. The temperature process is as follows: the temperature is raised from room temperature to 300℃±10℃, held for 2 hours, then raised to 700℃, and held for another 2 hours. The nitrogen flow rate is 2L / min and the heating rate is 4℃ / min throughout the heat treatment process.

[0142] Comparative Example 7

[0143] The difference from Example 1 is that the softening point of the asphalt is approximately 130°C.

[0144] Comparative Example 8

[0145] The difference from Example 1 is that the asphalt softening point is approximately 400°C.

[0146] Anode material performance testing:

[0147] 1. Electrochemical performance testing

[0148] The performance of the negative electrode materials in the examples and comparative examples was tested using a half-cell test method on a Blue Battery test system.

[0149] The negative electrode slurry ratio is: graphite:CMC:SP:SBR = 95:1.5:1.5:2. The slurry is coated onto copper foil, and the coated electrode is placed in a vacuum drying oven at 110℃ for 4 hours for later use. The electrolyte is 1 mol / L LiPF6 + EC:DEC:DM = 1:1:1 (volume ratio). A lithium metal sheet is used as the counter electrode, and a polypropylene microporous membrane is used as the separator. The battery is then assembled.

[0150] Charge and discharge regime: First, let stand for 2 hours; discharge: 0.1C to 0.09C, 0.08C, 0.07C…0.02C to 0.001V; let stand for 15 minutes; charge: 0.1C to 1.5V; let stand for 15 minutes.

[0151] 2. Particle size testing

[0152] The particle size of each material in the examples and comparative examples was tested using a Malvern 3000 laser particle size analyzer using a wet method.

[0153] 3. Asphalt thermal weight loss test

[0154] The thermal weight loss efficiency of asphalt with different softening points in a nitrogen atmosphere within the range of 50 to 1000℃ was tested using a German Netzsch thermogravimetric analyzer, which allows for precise control of the amount of asphalt used in the granulation process.

[0155] 4. Asphalt rheological property testing

[0156] The rheological properties of asphalt with different softening points under closed conditions were tested using a Shimadzu CFT-500EX capillary rheometer from Japan. This allowed us to understand the relationship between asphalt viscosity and temperature at different temperatures.

[0157] 5. Tap density test

[0158] The graphite in the glass graduated cylinder was vibrated 3000 times in a Canta tap density tester. The volume after vibration was calculated by the depth of descent, and the tap density was obtained by dividing the weight of the graphite by the volume after vibration.

[0159] 6. Specific surface area test

[0160] The adsorption isotherm of nitrogen on graphite within a certain temperature and pressure range was measured using a Beijing Jingwei High Wave Specific Surface Area Tester, and the specific surface area of ​​the material was then calculated.

[0161] The obtained data is shown in Table 1 below:

[0162] Table 1 Test Results of Anode Materials

[0163]

[0164] As shown in Table 1, after changing to the low-temperature granulation process, the electrochemical performance of the carbonized material was tested by sieving and selecting finished products with similar basic physical properties. The electrochemical performance of the low-temperature granulated product was better than that of the traditional carbonization process. Even after increasing the amount of asphalt, the new process performed better than the traditional process.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a high-rate artificial graphite anode material, characterized in that, include: Artificial graphite and asphalt are mixed, and then subjected to low-temperature granulation heat treatment under a protective atmosphere to obtain granulated material; the low-temperature granulation heat treatment includes a first heat treatment and a second heat treatment performed sequentially. The granulated material is carbonized to obtain the high-ratio artificial graphite anode material; The endpoint temperatures of the first heat treatment and the second heat treatment correspond to the metastable temperature range and viscosity abrupt change range of the rheological curve of the asphalt, respectively. The endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship: Y = BX + k; Where B is a calculation coefficient, ranging from 0.5 to 2.0, and is dimensionless; k is a calculation constant, ranging from 100 to 150℃. The endpoint temperature of the second heat treatment is not lower than the termination temperature at which the weight loss is complete in the thermogravimetric curve of the asphalt.

2. The method for preparing high-rate artificial graphite anode material according to claim 1, characterized in that, The endpoint temperature Y of the first heat treatment and the softening point X of the asphalt satisfy the following relationship: Y = X + 130℃.

3. The method for preparing high-rate artificial graphite anode material according to claim 1, characterized in that, One or more of the following conditions must be met: (1) The final temperature of the first heat treatment is 250-500℃, and the holding time is 1-3h; (2) The final temperature of the second heat treatment is 500-600℃, and the holding time is 1-3h; (3) The first heat treatment is performed by heating from room temperature to the final temperature at a heating rate not exceeding 10℃ / min; (4) The heating rate of the second heat treatment shall not exceed 10℃ / min; (5) The protective atmosphere includes nitrogen, and the flow rate of the nitrogen is 1-10 L / min; (6) During the low-temperature granulation heat treatment, the reaction vessel is kept under positive pressure; (7) During the low-temperature granulation heat treatment, the material is in motion; (8) The carbonization treatment temperature is 900-1200℃, the time is 2-6h, and the heating rate is not higher than 6℃ / min; (9) The D50 particle size of the artificial graphite is 8-11 μm, and the D50 particle size of the asphalt is not higher than 5 μm; (10) The softening point of the asphalt is 150-380℃, and the residual carbon content of the asphalt after thermal weight loss is between 40-70%; (11) The asphalt includes coal-based asphalt and / or oil-based asphalt.

4. The method for preparing high-rate artificial graphite anode material according to any one of claims 1-3, characterized in that, One or more of the following conditions must be met: (1) The amount of the asphalt used is 2-8% of the total mass of the asphalt and the artificial graphite; (2) The mixing time shall not be less than 1 hour.

5. A high-rate artificial graphite anode material, characterized in that, It was prepared using the method for preparing high-rate artificial graphite anode material according to any one of claims 1-4.

6. The high-rate artificial graphite anode material according to claim 5, characterized in that, One or more of the following conditions must be met: (1) The high-rate artificial graphite anode material has a D10 of 5-7 μm, a D50 of 11-16 μm, and a D90 of 20-25 μm; (2) The tap density of the high-ratio artificial graphite anode material is 0.8-1.1 g / cm³. 3 ; (3) The specific surface area of ​​the high-ratio artificial graphite anode material is 0.9-1.3 m². 2 / g.

7. A lithium-ion battery, characterized in that, Including the high-rate artificial graphite anode material as described in claim 5 or 6.

8. An electrical-related device, characterized in that, Including the lithium-ion battery as described in claim 7.

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