Preparation Method of Graphite Anode Material, Anode Plate and Battery

Abstract

The present invention relates to the technical field of alkali metal ion batteries, and specifically provides a preparation method of a graphite negative electrode material, a negative electrode sheet and a battery. The preparation method of the graphite negative electrode material of the present invention includes: mixing pitch and quinoline insoluble matter to form a pitch mixture; heating the pitch mixture to obtain the graphite negative electrode material. In the present invention, during the coking process, quinoline insoluble matter is used as an additive to increase the content of quinoline insoluble matter in the pitch component, and the intercalated composite structure of the coking product is used to reduce the expansion rate of the prepared graphite negative electrode, which can significantly improve the cycle performance of the graphite negative electrode and will not cause problems such as deterioration of high-temperature storage performance. In addition, quinoline insoluble matter is a waste material generated during the pitch refining process and has a high economic value. The entire process is simple and the production cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of alkali metal ion batteries, and specifically provides a preparation method of a graphite negative electrode material, a negative electrode sheet, and an alkali metal ion battery. Background Art

[0002] As one of the main materials of the battery cell, the negative electrode has a significant impact on the cycle performance of the energy storage battery cell. By reducing the swelling of the graphite negative electrode material, it is possible to reduce the consumption of active lithium due to the fragmentation and recombination of the SEI during the cycle, and at the same time reduce the swelling stress during the cycle, which is beneficial to the exertion of its kinetic performance, reduce the risk of lithium plating during the cycle, and greatly improve its cycle performance.

[0003] Currently, methods for reducing the swelling of graphite negative electrodes include amorphous carbon coating, reducing the particle size of graphite negative electrodes, etc., or through the isostatic pressing graphite process (increasing the orientation of graphite by batching, kneading, and isostatic pressing). These modification methods are mostly process optimizations and do not improve from the coke raw materials, and there will be some obvious drawbacks. For example, amorphous carbon coating and particle size reduction can reduce the swelling of graphite, but will significantly deteriorate the high-temperature storage performance; while the isostatic pressing graphite process increases the orientation of graphite to reduce swelling, but the whole process is relatively cumbersome and the production cost is high.

[0004] There is a need to develop a graphite negative electrode material that can significantly improve the cycle performance of graphite negative electrodes, with a simple and efficient overall production process and no deterioration of high-temperature storage performance. Summary of the Invention

[0005] In order to overcome the above defects, the present invention proposes a preparation method of a graphite negative electrode material, a negative electrode sheet, and a battery.

[0006] In a first aspect, the present invention provides a preparation method of a graphite negative electrode material, including:

[0007] Mix asphalt and quinoline insoluble matter to form an asphalt mixture;

[0008] Heat-treat the asphalt mixture to obtain a graphite negative electrode material.

[0009] Further, the softening point of the asphalt is 55 - 90°C.

[0010] Further, the mass ratio of the asphalt to the quinoline insoluble matter is (80 - 90):(10 - 20).

[0011] Further, the heat-treating the asphalt mixture includes:

[0012] Treat the asphalt mixture under a preset pressure and a first preset temperature to obtain green coke;

[0013] Treat the green coke at a second preset temperature to obtain pitch coke;

[0014] Obtain a graphite anode material based on the pitch coke.

[0015] Further, the step of treating the asphalt mixture at a preset pressure and a first preset temperature to obtain green coke includes:

[0016] Heat-treat the asphalt mixture at 1.5 - 2.0 MPa and 450 - 550 °C for 100 min - 200 min to obtain green coke.

[0017] Further, the step of treating the green coke at a second preset temperature to obtain pitch coke includes:

[0018] Heat-treat the green coke at 700 - 900 °C for 80 min - 120 min to obtain pitch coke.

[0019] Further, the step of obtaining a graphite anode material based on the pitch coke includes:

[0020] Crush, shape, and graphitize the pitch coke to obtain a graphite anode material.

[0021] Further, the obtained graphite anode material has a particle size D50 = 8.5 - 10.5 μm and a graphitization degree = 87% - 91%.

[0022] In a second aspect, the present invention provides a negative electrode tab, which includes a negative electrode current collector, and the graphite anode material as described in the first aspect is coated on the negative electrode current collector.

[0023] In a third aspect, the present invention provides an alkali metal ion battery, which includes a battery case, and an electrolyte, a positive electrode tab, a separator, and the negative electrode tab as described in the second aspect located inside the battery case.

[0024] One or more of the above technical solutions of the present invention have at least one or more of the following beneficial effects:

[0025] In implementing the technical solution of the present invention, by using quinoline insoluble matter as an additive during the coking process, increasing the content of quinoline insoluble matter in the asphalt component, and the inlaid combination structure of the coking product to reduce the expansion rate of the prepared graphite anode, the cycle performance of the graphite anode can be significantly improved, and problems such as deterioration of the high-temperature storage performance will not occur.

[0026] In addition, quinoline insoluble matter is a waste material generated during the asphalt refining process, which has a high economic value, and the entire process is simple and the production cost is low. Description of the Drawings

[0027] Referring to the accompanying drawings, the disclosure of the present invention will become more readily understandable. It is readily understandable to those skilled in the art that these drawings are merely for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, where:

[0028] Figure 1 is a schematic flow chart of the main steps of a method for preparing a graphite negative electrode material according to an embodiment of the present invention;

[0029] Figure 2 is a schematic flow chart of the main steps of obtaining a graphite negative electrode material from an asphalt mixture according to an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram for optimizing the content of the mosaic structure during the pitch coking process of quinoline insoluble matter according to an embodiment of the present invention. Detailed Embodiments

[0031] Some embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0032] The present invention provides a method for preparing a graphite negative electrode material. Referring to Figure 1 , including:

[0033] S1, mixing pitch and quinoline insoluble matter to form an asphalt mixture;

[0034] S2, subjecting the asphalt mixture to a heat treatment to obtain a graphite negative electrode material.

[0035] The present invention aims to solve the problem of rapid decline in cycle performance of graphite negative electrodes due to excessive volume expansion during cycling. To achieve this goal, a certain amount of QI (Quinoline Insolubles) is added during the pitch coking process of the present invention. By preventing the growth and coalescence of mesophase spheres during the liquid-phase carbonization process, it helps the coke to form more mosaic structures, so that the graphite negative electrode material produced from the asphalt mixture has a lower expansion rate. Such a graphite negative electrode material performs excellently in terms of cycle performance and can significantly improve the cycle stability of the battery. In addition, the entire production process is not only simple but also efficient, and has good industrial application prospects.

[0036] In one embodiment, the quinoline-insoluble matter is the waste material extracted during the asphalt refining process. In the present invention, before coking, QI needs to be mixed into the asphalt, and the added QI is the waste material extracted during the asphalt refining process. The overall production cost is low and the economic value is high. This approach not only effectively utilizes the materials that would otherwise be discarded, but also reduces environmental pollution, achieving a double improvement in resource reuse and economic benefits.

[0037] In one embodiment, the asphalt is low-temperature coal tar pitch. More specifically, the softening point of the asphalt is 55-90°C.

[0038] In one embodiment, in step S1, first, the asphalt and quinoline-insoluble matter are weighed respectively according to the mass ratio of asphalt to quinoline-insoluble matter of (80-90):(10-20), and then the asphalt and quinoline-insoluble matter are added to a mixer and mixed evenly.

[0039] In one embodiment, referring to Figure 2 , step S2, the heating treatment of the asphalt mixture to obtain the graphite anode material includes:

[0040] S21, treating the asphalt mixture under a preset pressure and a first preset temperature to obtain green coke;

[0041] S22, treating the green coke at a second preset temperature to obtain pitch coke;

[0042] S23, obtaining the graphite anode material based on the pitch coke.

[0043] In one embodiment, in step S21, treating the asphalt mixture under a preset pressure and a first preset temperature to obtain green coke includes:

[0044] The asphalt mixture is heat-treated at 1.5-2.0 MPa and 450-550°C for 100 min-200 min to obtain green coke.

[0045] Through the above high-temperature and high-pressure reaction process, green coke is obtained from the asphalt mixture.

[0046] In one embodiment, in step S22, treating the green coke at a second preset temperature to obtain pitch coke includes:

[0047] The green coke is heat-treated at 700-900°C for 80 min-120 min to obtain pitch coke.

[0048] Through the above heat treatment at high temperature, pitch coke is obtained from green coke.

[0049] Asphalt is a dark brown complex mixture composed of hydrocarbon compounds with different molecular weights and their non-metallic derivatives. It is a kind of high-viscosity organic liquid, in a liquid state, with a black surface, and is soluble in carbon disulfide. Asphalt is an organic cementing material for waterproofing, moisture-proofing and anti-corrosion.

[0050] Green coke is the residue obtained by deep cracking of raw materials such as petroleum residue, coal tar, asphalt, etc. by the coking method, and is a porous coke material.

[0051] Pitch coke is the solid residue obtained after high-temperature dry distillation or delayed coking of coal tar pitch.

[0052] In one embodiment, in step S23, the obtaining of the graphite anode material based on the pitch coke includes:

[0053] Crushing, shaping and graphitizing the pitch coke to obtain the graphite anode material.

[0054] In one application scenario, the crushing process includes: using a mechanical crusher to crush the pitch coke to the target particle size.

[0055] The shaping process includes: using a shaping machine to grind and shape the edges and corners of the crushed pitch coke to improve the regularity of the particle morphology and reduce the particle edges and corners; the graphitizing process includes: using a graphitizing furnace to perform high-temperature heat treatment on the shaped pitch coke at 2800°C - 3100°C.

[0056] In one embodiment, the obtained graphite anode material has a particle size D50 = 8.5 - 10.5 μm and a graphitization degree = 87% - 91%.

[0057] In one application scenario, the preparation method of the present invention first adds medium and low temperature coal tar pitch and quinoline insoluble matter into a mixer in a certain mass ratio and mixes them evenly to obtain an asphalt mixture; then adds the asphalt mixture into a high-pressure reactor, and puts the high-pressure reactor into a heating furnace for heat treatment to obtain green coke; then puts the green coke into a roasting furnace for high-temperature heat treatment to obtain pitch coke with a fine mosaic structure; finally, the pitch coke is processed through crushing, shaping and graphitization processes to obtain a low-expansion graphite anode material.

[0058] The present invention also provides a negative electrode sheet, including a negative electrode current collector, and the graphite anode material as described above is coated on the negative electrode current collector.

[0059] The present invention also provides an alkali metal ion battery, including a battery case and an electrolyte, a positive electrode sheet, a separator and the negative electrode sheet located inside the battery case.

[0060] In one embodiment, the alkali metal ion battery of the present invention includes, but is not limited to, lithium ion batteries, sodium ion batteries and potassium ion batteries.

[0061] The preparation method of the present invention is adopted below to prepare a graphite negative electrode material, and a negative electrode sheet and a battery are made therefrom.

[0062] Example 1: Mesophase pitch with a softening point of 80 °C and quinoline insoluble matter were mixed in a mass ratio of 85:15 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 500 °C for heat treatment for 120 min to obtain green coke. During the process, the pressure in the high-pressure reactor was controlled at 1.8 - 2.0 MPa; then the green coke was placed in a roasting furnace and heated to 850 °C for heat treatment for 100 min to obtain pitch coke. Then the pitch coke was subjected to crushing, shaping, and graphitization treatments to obtain a low-expansion graphite negative electrode material with D50 = 9.5 μm and a graphitization degree of 89%.

[0063] The low-expansion graphite negative electrode material obtained in Example 1, SP (conductive carbon black), CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and a negative electrode sheet was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a positive electrode sheet, electrolyte and other materials into a 2 Ah soft-pack lithium-ion battery.

[0064] Example 2: Mesophase pitch with a softening point of 65 °C and quinoline insoluble matter were mixed in a mass ratio of 85:15 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 500 °C for heat treatment for 120 min to obtain green coke. During the process, the pressure in the high-pressure reactor was controlled at 1.8 - 2.0 MPa; then the green coke was placed in a roasting furnace and heated to 850 °C for heat treatment for 100 min to obtain pitch coke. Then the pitch coke was subjected to crushing, shaping, and graphitization treatments to obtain a low-expansion graphite negative electrode material with D50 = 9.5 μm and a graphitization degree of 89%.

[0065] The low-expansion graphite negative electrode material obtained in Example 2, SP, CMC, and SBR were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and a negative electrode sheet was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a positive electrode sheet, electrolyte and other materials into a 2 Ah soft-pack lithium-ion battery.

[0066] Example 3: Medium-temperature pitch with a softening point of 80 °C and quinoline insoluble matter were mixed in a mass ratio of 90:10 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 500 °C for heat treatment for 120 min to obtain green coke. During the process, the pressure in the high-pressure reactor was controlled at 1.8 - 2.0 MPa; then the green coke was placed in a roasting furnace and heated to 850 °C for heat treatment for 100 min to obtain pitch coke. Then the pitch coke was subjected to crushing, shaping, and graphitization treatments to obtain a low-expansion graphite anode material with D50 = 9.5 μm and a graphitization degree of 90%.

[0067] The low-expansion graphite anode material, SP, CMC, and SBR obtained in Example 3 were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and a negative electrode sheet was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a positive electrode sheet, electrolyte, and other materials into a 2 Ah soft-pack lithium-ion battery.

[0068] Example 4: Medium-temperature pitch with a softening point of 80 °C and quinoline insoluble matter were mixed in a mass ratio of 85:15 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 500 °C for heat treatment for 120 min to obtain green coke. During the process, the pressure in the high-pressure reactor was controlled at 1.5 - 1.8 MPa; then the green coke was placed in a roasting furnace and heated to 850 °C for heat treatment for 100 min to obtain pitch coke. Then the pitch coke was subjected to crushing, shaping, and graphitization treatments to obtain a low-expansion graphite anode material with D50 = 10.5 μm and a graphitization degree of 89%.

[0069] The low-expansion graphite anode material, SP, CMC, and SBR obtained in Example 4 were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and a negative electrode sheet was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a positive electrode sheet, electrolyte, and other materials into a 2 Ah soft-pack lithium-ion battery.

[0070] Example 5: Medium-temperature pitch with a softening point of 55 °C and quinoline insoluble matter were mixed in a mass ratio of 80:20 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 450 °C for heat treatment for 200 min to obtain green coke. During the process, the pressure in the high-pressure reactor was controlled at 1.5 - 1.8 MPa; then the green coke was placed in a roasting furnace and heated to 900 °C for heat treatment for 80 min to obtain pitch coke. Then the pitch coke was subjected to crushing, shaping, and graphitization treatments to obtain a low-expansion graphite anode material with D50 = 8.5 μm and a graphitization degree of 87%.

[0071] The low-expansion graphite anode material obtained in Example 5, SP (conductive carbon black), CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and then an anode electrode was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a cathode electrode, electrolyte and other materials into a 2 Ah soft-pack lithium-ion battery.

[0072] Example 6: Mesophase pitch with a softening point of 90 °C and quinoline insoluble matter were mixed in a mass ratio of 83:12 to obtain an asphalt mixture; then the asphalt mixture was added to a high-pressure reactor, and the high-pressure reactor was placed in a heating furnace and heated to 550 °C for heat treatment for 100 min to obtain green coke, and the pressure in the high-pressure reactor was controlled at 1.5 - 1.8 MPa during the process; then the green coke was placed in a roasting furnace and heated to 700 °C for heat treatment for 120 min to obtain pitch coke. Then the pitch coke was crushed, shaped, and graphitized to obtain a low-expansion graphite anode material with D50 = 9.5 μm and a graphitization degree of 87%.

[0073] The low-expansion graphite anode material obtained in Example 6, SP (conductive carbon black), CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were mixed and homogenized in a mass ratio of 94.0:3.0:1.0:2.0, and then an anode electrode was prepared through processes such as coating, drying, and rolling. Then, it was assembled with a cathode electrode, electrolyte and other materials into a 2 Ah soft-pack lithium-ion battery.

[0074] Comparative Example 1: The crushed and shaped artificial graphite powder was screened, and the artificial graphite powder with a particle size ≤ 10 μm was selected for use. 35 kg of asphalt in a molten state at 200 °C was added to 65 kg of artificial graphite powder with a particle size ≤ 10 μm, and kneading treatment was carried out. The heating temperature during the kneading process was 250 °C, and the kneading time was 90 min. All the kneaded raw materials were transferred to an isostatic pressing mold, evacuated to 40 KPa, and then transferred to an isostatic press for molding to obtain a green body. The green body was placed in a crucible, and then the crucible was transferred to a vacuum roasting furnace. In the temperature rising range of 100 °C to 350 °C, the heating rate was 1.0 °C / h, in the temperature rising range of 350 °C to 600 °C, the heating rate was 0.5 °C / h, in the temperature rising range of 600 °C to 900 °C, the heating rate was 1.5 °C / h, and in the temperature rising range of 900 °C to 1300 °C, the heating rate was 2.0 °C / h. The roasted blank was graphitized, first heated to 1500 °C, held for 4 h, then evenly heated to 2800 °C, and finally cooled to 90 °C at a cooling rate of 1.0 °C / h and taken out of the furnace to obtain a low-expansion graphite material.

[0075] The low-expansion graphite anode material, SP, CMC, and SBR obtained in Comparative Example 1 were mixed and homogenized at a mass ratio of 94.0:3.0:1.0:2.0, and an anode electrode sheet was prepared through processes such as coating, drying, and rolling. Then, it was assembled into a 2 Ah soft-pack battery together with materials such as a cathode sheet and an electrolyte. The difference between Comparative Example 1 and the Examples lies only in the preparation process of the graphite anode material, and other aspects such as the materials of the cathode sheet and the electrolyte, as well as processes such as coating, drying, and rolling, are the same. The differences between Examples 1-6 lie only in the parameters of the preparation process of the graphite anode material.

[0076] The batteries prepared in the above Examples and Comparative Examples were tested. The test items included: full charge expansion rate %, 1C / 1C capacity retention rate % at 25°C for 1000 cycles, and capacity retention rate % after storage at 60°C for 100 days.

[0077] The test results are shown in Table 1.

[0078] Table 1 Test results of the batteries in the Examples and Comparative Examples

[0079]

[0080] By analyzing the test data in Table 1 in detail, it can be clearly observed that compared with Comparative Example 1, the Examples show significant advantages in the full charge expansion rate of the anode. Specifically, under the same test conditions, after 1000 charge-discharge cycles of the anode materials in the Examples, their capacity retention rates not only did not show a significant decline, but instead stably maintained above 96.7%. In contrast, under the same conditions, the capacity of the battery in Comparative Example 1 decayed more significantly, and the capacity retention rate after 1000 cycles was only 94.3%. In addition, in the high-temperature storage test, the Examples also showed higher thermal stability and longer service life. At a storage temperature of 60°C, after 100 days of storage, the capacity retention rate of the batteries in the Examples was still as high as above 92.9%, while the battery in Comparative Example 1 showed more obvious capacity decay, and the capacity retention rate was only 90.3%.

[0081] It can be seen that the full charge expansion rate of the anode in the Examples is significantly lower, indicating that the degree of volume expansion during charging to the full charge state is smaller. The expansion rate is one of the important parameters for measuring the quality of lithium-ion battery anode materials, and there is a positive correlation between the anode expansion rate and the cycle life of the battery. It is not only directly related to the cycle life of the battery, but also an important guarantee for the safety of the battery. If the volume of the anode material changes too much during the charge-discharge process, it will inevitably cause irreversible damage to the internal structure of the battery, thereby affecting the number of cycle uses and the overall performance of the battery. The low full charge expansion rate shown by the Examples is an intuitive manifestation of the excellent performance of their anode materials and a strong proof of their higher safety.

[0082] To more comprehensively evaluate the performance differences between these two anode materials, high-temperature storage tests were also conducted. Under extreme conditions, that is, after storing for 100 days in a high-temperature environment of 60 °C, the batteries of the examples once again demonstrated more superior performance. The battery capacity retention rate remained strong, up to over 92.9%, and was less affected by the high-temperature environment. This result not only proves the stability of the material in a high-temperature environment but also indicates its broad prospects in practical applications. In contrast, for the battery of Comparative Example 1, the capacity decay was more obvious in this test, and the capacity retention rate after storing for 100 days was only 90.3%. It can be seen that the batteries of the examples also had a significant improvement in cycle performance and high-temperature storage performance. The improvement of these performances is mainly attributed to the fact that the examples started from optimizing the organizational structure of the coke raw materials. By adding quinoline insoluble matter and increasing the proportion of the fine mosaic organizational structure of the coke, a graphite anode material with good orientation and a lower expansion rate was successfully prepared. This graphite anode material not only has higher structural stability, can effectively resist volume changes during charge and discharge, but also can maintain excellent performance in a high-temperature environment, providing a solid support for the wide application of lithium-ion batteries.

[0083] Compared with the optimization processes of graphite anodes such as asphalt filling and coating in the comparative examples, the processing technology of the examples of the present invention is more simple and efficient. This simple and efficient processing technology not only significantly improves the cycle performance but also performs well in high-temperature storage performance and does not show deterioration. This shows that the examples of the present invention have unique advantages in optimizing the performance of graphite anode materials, can effectively solve the problems existing in traditional processes, and provide a new idea and method for the preparation of graphite anode materials.

[0084] In the coking process of the present invention, quinoline insoluble matter (QI) was cleverly used as an additive. By increasing the content of quinoline insoluble matter in the asphalt component, the mosaic combination structure of the coke product was optimized, as Figure 3 shown, in the pitch coke prepared by the present invention, the content of the mosaic organizational structure is above 80%, and it has good isotropy.

[0085] The present invention creatively uses the component QI, which is usually regarded as industrial waste in the prior art or the component QI that is usually considered to be removed, as an additive and adds it to the pitch coking process in an appropriate doping amount. In traditional concepts, due to its difficult treatment and possible adverse effects on product quality, it is often regarded as useless. However, this invention takes a unique approach to utilize this "waste". Through scientific formulation design and process optimization, it becomes a key additive to improve the quality of pitch coking. This unique method can effectively prevent the growth and coalescence of mesophase spheres during the liquid-phase carbonization process in the pitch coking process. Through this technical means, the coke raw material can form more mosaic tissue structures, so that the graphite anode material prepared from this coke raw material has a lower expansion rate and excellent cycling performance.

[0086] This innovative method significantly reduces the expansion rate of the prepared graphite anode, thus greatly improving the cycling performance of the graphite anode. More importantly, this method does not cause problems such as deterioration of high-temperature storage performance, ensuring the stability and reliability of the battery.

[0087] In addition, quinoline insoluble matter is actually waste material generated during the pitch refining process and has high economic value. Therefore, the present invention not only has significant advantages technically, but also has high feasibility economically. The whole process is simple, the production cost is low, and it has good market application prospects.

[0088] It is worth noting that with the increasing demand for high-energy-density and long-life batteries in fields such as electric vehicles and energy storage systems, the excellent performance shown by the batteries prepared using the anode material of the present invention undoubtedly provides strong support for the development of these fields.

[0089] It should be pointed out that although the above embodiments describe the various steps in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, it is not necessary for different steps to be executed in such an order. They can be executed simultaneously (in parallel) or in other orders, and these changes are all within the protection scope of the present invention.

[0090] So far, the technical solution of the present invention has been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A method for preparing a graphite negative electrode material, characterized in that: include: mixing asphalt and quinoline insoluble matter to form an asphalt mixture; The asphalt mixture is subjected to a heating treatment to obtain a graphite negative electrode material; The heating treatment of the asphalt mixture comprises: Processing the asphalt mixture at a preset pressure and a first preset temperature to obtain green coke; treating the raw coke at a second preset temperature to obtain pitch coke; Obtaining a graphite negative electrode material based on the pitch coke; The step of treating the asphalt mixture at a preset pressure and a first preset temperature to obtain green coke comprises: heat treating the asphalt mixture at 1.5-2.0 MPa and 450-550° C. for 100 min-200 min to obtain green coke.

2. The method according to claim 1, characterized in that The softening point of the asphalt is 55-90°C.

3. The method according to claim 1, characterized in that The mass ratio of the asphalt to the quinoline insoluble matter is (80-90):(10-20).

4. The method according to claim 1, characterized in that: The step of treating the green coke at the second preset temperature to obtain pitch coke comprises: heat treating the green coke at 700-900° C. for 80 min-120 min to obtain pitch coke.

5. The method according to claim 1, characterized in that The method of obtaining the graphite negative electrode material based on the pitch coke comprises: subjecting the pitch coke to crushing, shaping and graphitizing treatment to obtain the graphite negative electrode material.

6. The method according to claim 1, characterized in that The obtained graphite negative electrode material has a particle size D50 of 8.5-10.5 μm and a graphitization degree of 87%-91%.

7. A negative electrode plate, characterized in that: The invention comprises a negative electrode current collector, on which the graphite negative electrode material according to any one of claims 1 to 6 is coated.

8. An alkali metal ion battery, characterized in that: It comprises a battery casing, an electrolyte, a positive electrode sheet, a separator and a negative electrode sheet as claimed in claim 7, which are located in the battery casing.

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