Artificial graphite negative electrode material, preparation method thereof, negative electrode sheet and battery

Abstract

The present application relates to a kind of artificial graphite negative electrode material and its preparation method, negative electrode sheet and battery.The preparation method includes the following steps: coarse breaking raw material coke, and the raw material coke after coarse breaking is high-temperature pretreatment;The raw material coke after pretreatment is crushed and shaped and is handled, and obtains primary particle A;Primary particle A is mixed with aqueous binder and is ball milled, and material B is obtained;Material B is dried and handled, and obtains secondary particle precursor C;Secondary particle precursor C is graphitized and handled, and obtains secondary particle finished product, i.e.the negative electrode material.The preparation method of the present application, compared with conventional granulation mode, significantly improves the specific capacity of negative electrode material, initial efficiency and high-temperature performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to an artificial graphite negative electrode material, a preparation method thereof, a negative electrode sheet and a battery. BACKGROUND

[0002] With the development of technology, the current market has higher and higher requirements for battery technology, especially the fast charging capability and high temperature storage performance of the battery. The improvement of the fast charging capability and the improvement of the high temperature storage performance are usually in opposite design directions in the battery, so it is difficult to achieve the improvement of the fast charging capability and the improvement of the high temperature storage performance.

[0003] The design of the negative electrode material greatly determines the fast charging capability and the high temperature storage performance of the battery. The most widely used at present is an artificial graphite negative electrode material. Artificial graphite usually uses a granulation method to prepare secondary particles to improve the fast charging capability and reduce the sheet rebound. However, a granulation binder (such as pitch) needs to be added for the bonding of primary particles during the granulation process. The binder has a lower graphitization degree than graphite, a high surface defect, and is easy to react with the electrolyte, resulting in the deterioration of the high temperature performance of the battery.

[0004] When the binder content is high during granulation, the material has better fast charging capability and lower sheet rebound rate, but the high temperature storage performance deteriorates significantly. When the binder content is low during granulation, the high temperature storage performance of the material deteriorates less, but the fast charging capability and the sheet rebound rate of the material also change little. Therefore, there is an urgent need for an artificial graphite negative electrode material that can bond more primary particles at a lower binder addition amount, improve the high temperature performance while ensuring the fast charging capability and the rebound rate of the material.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] To solve the above technical problems, the present application provides an artificial graphite negative electrode material, a preparation method thereof, a negative electrode sheet and a battery. The preparation process of the artificial graphite negative electrode material provided by the present application significantly improves the specific capacity, the initial efficiency and the high temperature performance of the negative electrode material compared with the conventional granulation method.

[0007] The present application solves the above technical problems by the following technical solutions:

[0008] The first aspect of the present application provides a preparation method of a negative electrode material, comprising the following steps:

[0009] S1, coarsely crushing raw coke and pre-treating the coarsely crushed raw coke at high temperature;

[0010] S2, crushing and shaping the pre-treated raw coke in step S1 to obtain primary particles A;

[0011] S3, mixing and ball-milling the primary particles A obtained in step S2 with an aqueous binder to obtain material B;

[0012] S4, drying the material B obtained in step S3 to obtain secondary particle precursor C;

[0013] S5, graphitizing the secondary particle precursor C obtained in step S4 to obtain secondary particle product, i.e. the negative electrode material.

[0014] Preferably, in step S1, the raw material coke is selected from one or more of needle coke, petroleum coke, pitch coke;

[0015] Further preferably, in step S1, the raw material coke is petroleum coke.

[0016] Preferably, in step S1, the temperature of the high-temperature pretreatment is 1200-2000°C.

[0017] Further preferably, in step S1, the temperature of the high-temperature pretreatment is 1400-1800°C.

[0018] Preferably, in step S1, the time of the high-temperature pretreatment is 1-10h.

[0019] Further preferably, in step S1, the time of the high-temperature pretreatment is 4-6h.

[0020] Preferably, in step S2, the crushing and shaping treatment is performed using a roller pressing and shaping all-in-one machine.

[0021] Preferably, in step S2, the average particle size D50 of the primary particles A is 5-10μm.

[0022] Preferably, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(0.1-5.0).

[0023] Further preferably, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(0.5-2.5).

[0024] Further preferably, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(1.0-2.0).

[0025] Preferably, in step S3, the ball-milling is performed by a ball mill.

[0026] Preferably, in step S3, the rotation speed of the ball-milling is 50-200r / min.

[0027] Preferably, in step S3, the temperature of the ball milling is room temperature.

[0028] Preferably, in step S3, the time of the ball milling is 3-5h.

[0029] Preferably, in step S3, the aqueous binder is selected from a binder comprising one or more of carboxyl, hydroxyl, sulfonic acid group, phosphoric acid group, amino, carboxylate, etc.

[0030] Further preferably, in step S3, the aqueous binder is selected from a polyacrylic binder.

[0031] Further preferably, in step S3, the aqueous binder is selected from a polyacrylic acid.

[0032] Preferably, in step S3, the molecular weight of the aqueous binder ranges from 10000 to 100000.

[0033] Preferably, in step S4, the temperature of the drying treatment is 60-140℃.

[0034] Further preferably, in step S4, the temperature of the drying treatment is 80-120℃.

[0035] Preferably, in step S4, the time of the drying is 2-6h.

[0036] Further preferably, in step S4, the time of the drying is 3-5h.

[0037] Preferably, in step S5, the temperature of the graphitization treatment is 2500-3500℃.

[0038] Further preferably, in step S5, the temperature of the graphitization treatment is 2800-3300℃.

[0039] Preferably, in step S5, the time of the graphitization treatment is 12-36h.

[0040] Further preferably, in step S5, the time of the graphitization treatment is 15-25h.

[0041] The second aspect of the present application provides a negative electrode material, which is prepared according to the preparation method provided in the first aspect of the present application.

[0042] The third aspect of the present application provides a negative electrode sheet, which comprises the negative electrode material provided in the second aspect of the present application.

[0043] The fourth aspect of the present application provides a battery, which comprises the negative electrode sheet provided in the third aspect of the present application.

[0044] The preparation method of the artificial graphite negative electrode material provided by the application significantly improves the specific capacity, initial efficiency and high-temperature performance of the negative electrode material compared with conventional granulation methods.

[0045] The preparation method of the application maximizes the reduction of the amount of binder by adding the aqueous binder to bond the primary particles to form secondary particles at the surface functional group positions, ensures that the material after granulation has good high-temperature performance, and makes the primary particles have pores, thereby relieving volume expansion and enhancing the adaptability of the material.

[0046] The preparation method of the application controls the molecular weight range of the aqueous binder to be 10000-100000, which can ensure the binding performance of the binder on the particles, prevent the binder from having too large viscosity and poor flowability, and thus cause uneven coating of the binder on the surface functional groups of the primary particles.

[0047] The preparation method of the application controls the particle size volume distribution D50 of the primary particles to be in the range of 5-10um, which ensures strong fast-charging capability of the material on the basis of improving the yield of the primary particles and reducing the cost of the material.

[0048] Additional aspects and advantages of the application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0049] The drawings described herein are intended to provide further understanding of the application and constitute a part of the application. The illustrative embodiments of the application and their description serve to explain the application without forming an improper limitation on the application. In the drawings:

[0050] Figure 1 Structure schematic diagram of the artificial graphite negative electrode material prepared by the embodiment of the application. DETAILED DESCRIPTION

[0051] In order to make the technical solutions and beneficial effects of the application more obvious and easy to understand, the following will be described in detail by means of specific embodiments. It should be understood that the drawings are not necessarily drawn to scale, and local features can be enlarged or reduced to more clearly show the details of local features. It should be understood that these embodiments are only used to illustrate the application and do not limit the scope of the application. The experimental methods not specified in the following embodiments are usually carried out under conventional experimental conditions. The reagents and raw materials used in the application are commercially available unless otherwise specified.

[0052] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without one or more of these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the present application. According to the knowledge of those skilled in the art, there are many technical features in the present application, which are not described in detail in the present specification.

[0053] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0054] For a thorough understanding of the present application, reference will be made to the following detailed description, taken in conjunction with the accompanying drawings, in which: The preferred embodiments of the present application will be described in detail below with reference to the drawings. However, the present application can have other embodiments in addition to those described below.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0056] Unless otherwise indicated, conventional techniques and apparatuses of the art are employed in the examples below, unless otherwise indicated. Numerical ranges expressed in the format "from X to Y" are understood to include X and Y. When for example X 10, X is understood to be 10. When for example X to Y is recited, it is meant that an end point of a range is inclusive of the other end point of the range.

[0057] The first aspect of the present application provides a preparation method of a negative electrode material, comprising the following steps:

[0058] S1, coarsely breaking raw material coke and pre-treating the coarsely broken raw material coke at high temperature;

[0059] S2, crushing and shaping the pre-treated raw material coke in step S1 to obtain primary particles A;

[0060] S3, mixing and ball-milling the primary particles A obtained in step S2 with a water-based binder to obtain material B;

[0061] S4, drying the material B obtained in step S3 to obtain secondary particle precursor C;

[0062] S5, performing graphitization treatment on the secondary particle precursor C obtained in step S4 to obtain a secondary particle product, i.e., the negative electrode material.

[0063] In some embodiments, in step S1, the raw coke is selected from one or more of needle coke, petroleum coke, and pitch coke.

[0064] In some embodiments, in step S1, the raw coke is petroleum coke.

[0065] In some embodiments, in step S1, the high-temperature pretreatment is performed at a temperature of 1200-2000°C.

[0066] In some embodiments, in step S1, the high-temperature pretreatment is performed at a temperature of 1400-1800°C, for example, at 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, 1650°C, 1700°C, 1750°C, or 1800°C, but not limited to the listed values, and other values not listed in the range are also applicable.

[0067] In some embodiments, in step S1, the high-temperature pretreatment is performed for 1-10 h.

[0068] In some embodiments, in step S1, the high-temperature pretreatment is performed for 4-6 h, for example, for 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0069] In the embodiments of the present application, the primary particles A and the aqueous binder are only bonded at the positions of surface functional groups to form secondary particles, and the positions on the particle surface that do not contain functional groups are not coated with the binder, thereby reducing the amount of binder used during granulation. The surface reactivity of the binder is higher than the surface reactivity of the primary particles A, so this method can reduce the overall reactivity of the material after granulation, i.e., improve the high-temperature performance of the negative electrode material and the battery. In addition, the positions between the primary particles that are not coated with the binder form pores, which have the effects of relieving volume expansion, enhancing the adaptability of the material, and improving the service life of the battery.

[0070] In some embodiments, in step S2, the crushing and shaping treatment is performed using a roller pressing and grinding shaping all-in-one machine.

[0071] In some embodiments, in step S2, the average particle size D50 of the primary particles A is 5-10 μm, for example, it can be 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8.0 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9.0 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm or 10.0 μm, but not limited to the listed values, other values not listed in the value range are also applicable. In this way, the primary particles A can have a better specific surface area and activity, reducing the particle agglomeration or loss during the implementation process due to too small particle size, reducing the cost of preparing the negative electrode material, and being conducive to production; and also alleviating the problem of prolonging the lithium ion transmission path in the material due to too large particle size, thereby reducing the overall performance of the battery, and being conducive to ensuring the fast charging capacity of the battery.

[0072] In some embodiments, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(0.1-5.0).

[0073] In some embodiments, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(0.5-2.5).

[0074] In some embodiments, in step S3, the mass ratio of the primary particles A to the aqueous binder is 100:(1.0-2.0), for example, it can be 100:1.0, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9 or 100:2.0, but not limited to the listed values, other values not listed in the value range are also applicable.

[0075] In some embodiments, in step S3, the ball milling is carried out by a ball mill.

[0076] In some embodiments, in step S3, the rotation speed of the ball mill is 50-200 r / min, for example, it can be 50 r / min, 100 r / min, 150 r / min or 200 r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0077] In some embodiments, in step S3, the temperature of the ball mill is room temperature.

[0078] In some embodiments, in step S3, the temperature of the ball mill is room temperature.

[0079] In some embodiments, in step S3, the time of the ball mill is 3-5 h, for example, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0080] In some embodiments, in step S3, the aqueous binder is selected from a binder containing one or more of carboxyl, hydroxyl, sulfonic acid group, phosphoric acid group, amino, carboxylate and the like.

[0081] In some embodiments, in step S3, the aqueous binder is selected from a polyacrylic binder.

[0082] In some embodiments, in step S3, the aqueous binder is selected from a polyacrylic binder.

[0083] In some embodiments, in step S3, the aqueous binder is selected from a polyacrylic binder.

[0084] In some embodiments, in step S3, the molecular weight of the aqueous binder ranges from 10,000 to 100,000, for example, can be 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, or 100,000, but not limited to the listed values, other values not listed in the value range are also applicable. In this way, the problems of poor adhesion, insufficient adhesion strength, and inability to form a stable bonding interface caused by the molecular weight of the aqueous binder being less than 10,000 are solved, the connection between primary particles is tight and can maintain stable morphology and performance under external force, thereby improving the durability of the obtained negative electrode material and prolonging the service life of the battery; the problems of poor flowability and strong viscosity caused by the molecular weight of the aqueous binder being more than 100,000 are avoided, the binder can uniformly spread and penetrate into the small interstitial spaces between particles, which is beneficial to the uniform coating of the aqueous binder on the surface functional groups of the primary particles, and enhances the adaptability of the material, the service life and electrochemical performance of the battery.

[0085] In some embodiments, in step S4, the drying treatment is performed at a temperature of 60-140°C.

[0086] In some embodiments, in step S4, the drying treatment is performed at a temperature of 80-120°C, for example, 80°C, 90°C, 100°C, 110°C, or 120°C, but not limited to the listed values, other values not listed in the value range are also applicable. In this way, the problems of particle adhesion caused by binder softening and low inter-particle adhesion strength caused by excessively high drying temperature are effectively prevented, ensuring the stability of the overall structure of the negative electrode material and the service life of the battery; and the problems of affecting the evaporation rate of water caused by excessively low drying temperature, resulting in a significant reduction in drying efficiency, are effectively avoided, saving energy consumption and production cost of materials.

[0087] In some embodiments, in step S4, the drying treatment is performed at a heating rate of 2-7°C / min, for example, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, or 7°C / min, but not limited to the listed values, other values not listed in the value range are also applicable.

[0088] In some embodiments, in step S4, the drying time is 2-6h.

[0089] In some embodiments, in step S4, the drying time is 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0090] In some embodiments, in step S5, the graphitization temperature is 2500-3500℃.

[0091] In some embodiments, in step S5, the graphitization temperature is 2800-3300℃, for example, 2800℃, 2900℃, 3000℃, 3100℃, 3200℃ or 3300℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0092] In some embodiments, in step S5, the graphitization time is 12-36 hours.

[0093] In some embodiments, in step S5, the graphitization time is 15-25 hours, for example, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours or 25 hours, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0094] The second aspect of the present application provides a negative electrode material prepared according to the preparation method of the first aspect of the present application.

[0095] It should be understood that, since the negative electrode material provided by the present application is prepared according to the preparation method of the first aspect of the present application, the beneficial effects of preparing the negative electrode material in any of the above embodiments are applicable to the negative electrode material.

[0096] The third aspect of the present application provides a negative electrode sheet, which comprises the negative electrode material of the second aspect of the present application.

[0097] It should be understood that, since the negative electrode sheet provided by the present application comprises the negative electrode material of the second aspect of the present application, the beneficial effects of preparing the negative electrode material in any of the above embodiments are applicable to the negative electrode sheet.

[0098] The preparation method of the negative electrode sheet is not particularly limited in the present application, and a preparation method known in the art can be selected as long as the purpose of the present application can be achieved.

[0099] The fourth aspect of the present application provides a battery, which comprises the negative electrode sheet of the third aspect of the present application.

[0100] It should be understood that, since the battery provided by the present application comprises the negative electrode sheet according to the third aspect of the present application, the beneficial effects of preparing the negative electrode material in any of the above embodiments are applicable to the battery.

[0101] In some embodiments, the battery can be a secondary battery, which can be a lithium ion secondary battery. Generally, a secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing a role of preventing the short circuit of the positive electrode and the negative electrode, while allowing the ions to pass through.

[0102] The method of the present application is described below by means of specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present application, and the present application is not limited in scope by the following examples; the implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0103] Example 1

[0104] Petroleum coke was roughly broken to below 5 mesh, and then modified at a high temperature of 1500℃ for 5h. Then, the first particles A were obtained by crushing and shaping with a roller press all-in-one machine, and the average particle size D50 of the first particles A was controlled to be about 5μm, and the actual obtained particle size D50 result was 5.3μm. The first particles A and a polyacrylic acid binder were put into a ball mill at a mass ratio of 100:2, and ball-milled at a rotation speed of 100r / min at room temperature for 4h to obtain material B. The material B was placed in an oven, and heated to 100℃ at a heating rate of 3℃ / min, and then kept at 100℃ for 4h, and then cooled and sieved to obtain the second particle precursor C. The second particle precursor C was graphitized at 3000℃ for 20h, and sieved to obtain the second particle material with a particle size D50 of 9.9μm, i.e. the artificial graphite negative electrode material.

[0105] Example 2

[0106] The petroleum coke is roughly broken to 5 mesh or less, and then modified at 1500℃ for 5h. Then, the first particle A is obtained by crushing and shaping with a roller press grinding and shaping integrated machine. The average particle size D50 of the first particle A is controlled to be about 8μm, and the actual particle size D50 result is 8.3μm. The first particle A and a polyacrylic acid binder are mixed in a mass ratio of 100:1 and put into a ball mill at room temperature at a speed of 100r / min for 4h to obtain material B. The material B is placed in an oven and heated to 100℃ at a heating rate of 3℃ / min, then kept for 4h, cooled and sieved to obtain the second particle precursor C. The second particle precursor C is graphitized at 3000℃ for 20h to obtain the second particle material with a particle size D50 of 12.1μm, i.e. the artificial graphite negative electrode material.

[0107] Example 3

[0108] The petroleum coke is roughly broken to 5 mesh or less, and then modified at 1500℃ for 5h. Then, the first particle A is obtained by crushing and shaping with a roller press grinding and shaping integrated machine. The average particle size D50 of the first particle A is controlled to be about 9μm, and the actual particle size D50 result is 8.1μm. The first particle A and a polyacrylic acid binder are mixed in a mass ratio of 100:1.8 and put into a ball mill at room temperature at a speed of 100r / min for 4h to obtain material B. The material B is placed in an oven and heated to 100℃ at a heating rate of 3℃ / min, then kept for 4h, cooled and sieved to obtain the second particle precursor C. The second particle precursor C is graphitized at 3000℃ for 20h to obtain the second particle material with a particle size D50 of 14.6μm, i.e. the artificial graphite negative electrode material.

[0109] Comparative Example 1

[0110] The petroleum coke is roughly broken to 5 mesh or less, and then modified at 1500℃ for 5h. Then, the first particle A is obtained by crushing and shaping with a roller press grinding and shaping integrated machine. The average particle size D50 of the first particle A is controlled to be about 5μm, and the actual particle size D50 result is 5.3μm. The first particle A and petroleum pitch with a softening point of 200℃ and an average particle size of 7μm are mixed in a mass ratio of 100:15, and then placed in a roller furnace for granulation reaction under nitrogen protection at a heating rate of 8℃ / min to 750℃ for 4h. After cooling and sieving, the second particle precursor C is obtained. The second particle precursor C is graphitized at 3000℃ for 20h to obtain the second particle material with a particle size D50 of 10.1μm, i.e. the artificial graphite negative electrode material.

[0111] Comparative Example 2

[0112] The petroleum coke was coarsely broken to 5 mesh or less, and then modified at 1500℃ for 5h. The first particle A was obtained by crushing and shaping with a roller press grinding and shaping integrated machine. The average particle size D50 of the first particle A was controlled to be about 8μm, and the actual particle size D50 result was 8.3μm. The first particle A and petroleum pitch with a softening point of 200℃ and an average particle size of 7μm were mixed uniformly at a mass ratio of 100:8, and then placed in a roller furnace. The granulation reaction was carried out under nitrogen protection at a temperature rising rate of 8℃ / min to 750℃ for 4h. The secondary particle precursor C was obtained by cooling and sieving.

[0113] Comparative Example 3

[0114] The petroleum coke was coarsely broken to 5 mesh or less, and then modified at 1500℃ for 5h. The first particle A was obtained by crushing and shaping with a roller press grinding and shaping integrated machine. The average particle size D50 of the first particle A was controlled to be about 9μm, and the actual particle size D50 result was 9.1μm. The first particle A and petroleum pitch with a softening point of 200℃ and an average particle size of 7μm were mixed uniformly at a mass ratio of 100:13, and then placed in a roller furnace. The granulation reaction was carried out under nitrogen protection at a temperature rising rate of 8℃ / min to 750℃ for 4h. The secondary particle precursor C was obtained by cooling and sieving.

[0115] Material performance test

[0116] The artificial graphite negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 were prepared into half-cells according to the following method:

[0117] The artificial graphite negative electrode materials, SP, CMC and SBR of Examples 1-3 and Comparative Examples 1-3 were weighed at a mass ratio of 95.5:1:1.5:2, respectively, and stirred uniformly in water to prepare a negative electrode slurry. The slurry was uniformly coated on a copper foil, and the coated electrode piece was placed in a vacuum drying oven at a temperature of 100℃ for vacuum drying for 4 hours, and then pressed to prepare a negative electrode.

[0118] A CR-2032 type button cell was assembled in an argon-filled German Mirolona glove box. A three-component mixed solvent of 1.2mol / L LiPF6 was used as the electrolyte, and the mixed solution was mixed at a volume ratio of EC:DMC:EMC=1:1:1. A metal lithium sheet was used as the electrode.

[0119] 1. Gravimetric capacity, first coulombic efficiency (initial efficiency) test: 0.05C discharge to 0.005V (denoted as C1), rest for 5min; 50μA discharge to 0.005V (denoted as C2), rest for 5min; 0.1C constant current charge to 2V (denoted as C0), rest for 5min, end the test. Gravimetric capacity (mAh / g) = C0(mAh) / mass of negative material (g); first coulombic efficiency = C0 / (C1+C2)*100%.

[0120] 2. High temperature cycle test: using a new Wei charge-discharge tester, first put the battery in a 45℃ oven, rest for 6h, so that the battery interior and the oven temperature reach thermal equilibrium; then carry out charge-discharge, the charge-discharge process is: 1C constant current charge to 3.65V, then constant voltage charge to 0.05V, rest for 10min, then 1C discharge to 2.5V, rest for 10min; record the discharge capacity at this time as the first cycle discharge capacity C0, record the capacity of each cycle during the battery cycle, the capacity of the nth cycle is Cn, the capacity retention rate of the nth cycle battery = Cn / C0*100%, which is the SOH of the battery at this time; record the cycle number when the battery reaches 80% SOH.

[0121] The results of gravimetric capacity, initial efficiency and high temperature cycle test are shown in Table 1.

[0122] Table 1

[0123]

[0124] From Table 1, it can be concluded that the artificial graphite negative material prepared in the embodiments of the present application has more excellent electrochemical performance: i.e. higher gravimetric capacity, better initial efficiency and more excellent high temperature performance. Specifically, comparing Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 3 with Comparative Example 3 respectively, it can be found that the gravimetric capacity and initial efficiency are improved to different degrees, and the high temperature performance is improved by 15.8% to 17.5% under the condition that the particle size of the secondary particles prepared does not change significantly and the amount of binder is less.

[0125] It should be understood that the above embodiments are exemplary and are not intended to include all possible embodiments encompassed by the claims. Various modifications and changes can also be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, any combination of the technical features of the above embodiments can also be made to form additional embodiments of the present application which have not been explicitly described. Therefore, the above embodiments only express several embodiments of the present application and do not limit the protection scope of the present application.

Claims

1. A method for producing a negative electrode material, characterized by, The method comprises the following steps: S1, coarsely crushing raw coke and performing high-temperature pretreatment on the coarsely crushed raw coke; S2, performing crushing and shaping treatment on the pretreated raw coke in step S1 to obtain primary particles A; S3, mixing and ball-milling the primary particles A obtained in step S2 with a water-based binder to obtain material B; S4, performing drying treatment on the material B obtained in step S3 to obtain secondary particle precursor C; S5, performing graphitization treatment on the secondary particle precursor C obtained in step S4 to obtain secondary particle finished product, i.e., the negative electrode material; The raw coke is selected from one or more of needle coke, petroleum coke, and pitch coke; The temperature of the high-temperature pretreatment is 1200-2000°C; The time of the high-temperature pretreatment is 1-10 h; The average particle size D50 of the primary particles A is 5-10 μm; The temperature of the ball-milling is room temperature; The mass ratio of the primary particles A to the water-based binder is 100:(1.0-2.0); The water-based binder is selected from polyacrylic acid; The molecular weight of the water-based binder ranges from 10000 to 100000.

2. The production method according to claim 1, characterized by, In step S1, the raw coke is petroleum coke.

3. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the high-temperature pretreatment is 1400-1800°C.

4. The preparation method according to claim 1, characterized in that, In step S1, the time of the high-temperature pretreatment is 4-6 h.

5. The preparation method according to claim 1, characterized in that, In step S2, the crushing and shaping treatment is performed by a roller pressing and shaping integrated machine.

6. The preparation method according to claim 1, characterized in that, In step S3, the ball-milling is performed by a ball mill.

7. The preparation method according to claim 1, characterized in that, In step S3, the rotation speed of the ball-milling is 50-200 r / min.

8. The method of claim 1, wherein, In step S3, the time of the ball-milling is 3-5 h.

9. The method of claim 1, wherein, In step S4, the temperature of the drying treatment is 60-140°C.

10. The method of claim 9, wherein, In step S4, the temperature of the drying treatment is 80-120°C.

11. The method of claim 1, wherein, In step S4, the time of the drying is 2-6 h.

12. The method of claim 11, wherein, In step S4, the time of the drying is 3-5 h.

13. The method of claim 1, wherein, In step S5, the temperature of the graphitization treatment is 2500-3500°C.

14. The method of claim 13, wherein, In step S5, the temperature of the graphitization treatment is 2800-3300°C.

15. The method of claim 1, wherein, In step S5, the time of the graphitization treatment is 12-36 h.

16. The method of claim 15, wherein, In step S5, the time of the graphitization treatment is 15-25 h.

17. A negative electrode material, characterized by, The negative electrode material is prepared according to the preparation method in any one of claims 1-16.

18. A negative electrode sheet characterized by comprising: The negative electrode tab comprises the negative electrode material in claim 17.

19. A battery, characterized by The battery comprises the negative electrode tab in claim 18.

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