A graphite anode material, its preparation method and application

Abstract

The present invention provides a graphite anode material, a preparation method thereof and an application. The graphite anode material includes primary particles and finished particles composed of a composite of primary particles and a binder. The particle sizes of the primary particles and the finished particles satisfy the relational expression k1 = K90 成品颗粒 / K90 一次颗粒 = 0.3 to 1.0, where K90 = (D90 - D10) / D50. The graphite anode material of the present invention has a high sphericity and a narrow particle size distribution. The tapped density of the anode material is relatively high. It not only has good performance but also has cost advantages and is more easily accepted by the market.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a graphite negative electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] The continuous reduction of the cost of power batteries is the driving force for the development of the new energy vehicle market. However, the cost of power batteries is still close to 40% of the whole vehicle. Along with the reduction of the subsidy amount for new energy vehicles and the improvement of the subsidy standard by the state, the performance requirements for batteries are getting higher and higher, especially for fast charging and endurance. It is necessary not only to greatly improve the performance, but also to greatly compress the cost. The improvement of the performance of power batteries is inseparable from the innovation of materials, especially the main lithium battery materials such as the positive electrode, separator, negative electrode, and electrolyte. Therefore, each material enterprise is constantly improving and enhancing the product performance.

[0003] For graphite negative electrode materials, the currently mainstream material structure designs include single particles, secondary particles, and a composite structure of these two types of particles. Secondary particles have isotropic characteristics and have advantages in lithium intercalation fast charging and expansion, but the tap density is relatively low, and it is difficult in the homogenization process of battery production. The lower solid content will also lead to an increase in production costs, and the preparation cost of graphite secondary particles is also relatively high, which will further hinder the reduction of battery costs. Single particles have poor isotropy, but good cycle and high-temperature performance, and a relatively high tap density. The production process is also simpler than that of secondary particles. Therefore, it has certain advantages in terms of cost, but the expansion and fast charging performance are poor.

[0004] CN107039654A discloses a preparation method of a high-capacity and long-cycle artificial graphite negative electrode material, which includes the following preparation steps: (1) raw material shaping treatment; (2) first mixing; (3) heat treatment; (4) graphitization; (5) second mixing; (6) carbonization heat treatment.

[0005] CN110380050A discloses a mixing process for preparing a high-tap-density microcrystalline graphite negative electrode material, which preliminarily mixes microcrystalline graphite and a coating agent, and then at room temperature, rotates and extrudes the microcrystalline graphite and the coating agent. Then, under a heating state, the mixture is rotated and extruded to press the coating agent into the mesopores and macropores of the microcrystalline graphite. Then, the extruded mixture is obtained through gas cooling, and then the obtained extruded mixture is subjected to graphitization treatment to obtain a high-tap-density microcrystalline graphite negative electrode material.

[0006] The methods for preparing graphite negative electrode materials in the above-mentioned solutions are complex, and the particle size distribution of the prepared graphite negative electrode materials is difficult to control, resulting in an increase in cost and poor battery performance after making the battery. Summary of the Invention

[0007] The object of the present invention is to provide a graphite anode material, a preparation method and an application thereof. The graphite anode material of the present invention has a high sphericity and a narrow particle size distribution. The tapped density of the anode material is relatively high. It not only has good performance, but also has cost advantages and is more easily accepted by the market.

[0008] To achieve the object of the present invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a graphite anode material, which includes primary particles and finished particles composed of a composite of primary particles and a binder. The particle sizes of the primary particles and the finished particles satisfy the relational expression k1 = K90 成品颗粒 / K90 一次颗粒 = 0.3 to 1.0 (for example: 0.3, 0.4, 0.5, 0.6, 0.8 or 1.0, etc.), where K90 = (D90 - D10) / D50.

[0010] The graphite anode material of the present invention can take into account the rate performance, compaction performance, cycling performance and high-temperature resistance performance, and can increase the solid content of the anode slurry and reduce the production cost.

[0011] Preferably, the tapped density of the graphite anode material is 1.2 to 1.4 g / cm 3 , for example: 1.2 g / cm 3 , 1.25 g / cm 3 , 1.3 g / cm 3 , 1.35 g / cm 3 or 1.4 g / cm 3 etc.

[0012] Preferably, the sphericity of the graphite anode material is 60 to 99%, for example: 60%, 70%, 80%, 90% or 99%, etc.

[0013] Preferably, the aspect ratio of the graphite anode material is (0.50 to 0.99):1, for example: 0.5:1, 0.6:1, 0.7:1, 0.8:1 or 0.99:1, etc.

[0014] Preferably, the binder includes any one or a combination of at least two of asphalt, resin, tar or paraffin oil.

[0015] In the second aspect, the present invention provides a preparation method of the graphite anode material as described in the first aspect. The preparation method includes the following steps:

[0016] (1) After crushing the carbon material, powder A is obtained. The powder A is mixed with a binder and then sintered to obtain block B;

[0017] (2) Crush the block material B obtained in step (1) to obtain a powder material C, and perform graphitization treatment on the powder material C to obtain the graphite negative electrode material.

[0018] In the present invention, the carbon source material is pre-crushed to the target particle size, mixed with a binder and then sintered into a block at a high temperature, and then mechanically crushed to a target particle size similar to the previous one. Since the binder fills the particle surface and the secondary grinding of the crushing equipment, the particle surface can be made more round.

[0019] Preferably, the carbon material in step (1) includes any one or at least two combinations of petroleum coke, needle coke, pitch coke, coke or coal.

[0020] Preferably, the crushing method includes any one or at least two combinations of extrusion, impact or friction.

[0021] Preferably, the mass ratio of the powder material A to the binder is 100:(1-50), for example: 100:1, 100:5, 100:10, 100:20 or 100:50, etc., preferably 100:(1-30).

[0022] Preferably, the temperature of the sintering treatment is 400-1650 °C, for example: 400 °C, 500 °C, 1000 °C, 1200 °C or 1650 °C, etc., preferably 600-900 °C.

[0023] Preferably, the median particle size D50 of the powder material A is 4-20 μm, for example: 4 μm, 8 μm, 10 μm, 12 μm, 15 μm or 20 μm, etc.

[0024] Preferably, the difference between the median particle size D50 of the powder material C in step (2) and the median particle size D50 of the powder material A is ≤2 μm.

[0025] Preferably, the particle sizes of the powder material C and the powder material A satisfy the relationship k2 = K90 粉料C / K90 粉料A = 0.3-1.0, for example: 0.3, 0.4, 0.5, 0.6, 0.8 or 1.0, etc.

[0026] In the third aspect, the present invention provides a negative electrode sheet, and the negative electrode sheet includes the graphite negative electrode material as described in the first aspect.

[0027] In the fourth aspect, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the negative electrode sheet as described in the third aspect.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The sphericality of the graphite anode material described in the present invention is high and the particle size distribution is relatively narrow. The tap density of the anode material is relatively high. It not only has good performance, but also has cost advantages and is more easily accepted by the market.

[0030] (2) The tap density of the graphite anode material described in the present invention can reach 1.2 g / cm 3 or more, the sphericality can reach 60% or more, and the aspect ratio can reach 67% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic process flow diagram of the preparation of the graphite anode material described in Example 1.

[0032] Figure 2 is an SEM image of Powder C described in Example 1.

[0033] Figure 3 is an SEM image of the graphite anode material described in Example 1.

[0034] Figure 4 is an SEM image of the graphite anode material described in Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0036] Example 1

[0037] This example provides a graphite anode material, which is prepared by the following method. The process flow diagram of the method is as Figure 1 shown:

[0038] (1) Needle coke is crushed by extrusion pressure to obtain Powder A with a median particle size D50 = 9.0 μm. Powder A and an asphalt binder are mixed at a mass ratio of 100:25 and sintered at 950 °C. After cooling, block B is obtained, where K90 粉料A = 1.53;

[0039] (2) Block B is crushed by impact force and friction force to obtain Powder C with a median particle size D50 = 10 μm. Powder C is loaded into a graphitization furnace and graphitized to obtain the graphite anode material, where K90 粉料C = 1, K90 成品颗粒 = 0.99. The SEM image of the Powder C is as Figure 2 shown, and the SEM image of the graphite anode material is as Figure 3 shown.

[0040] Example 2

[0041] This embodiment provides a graphite anode material, which is prepared by the following method:

[0042] (1) The petroleum coke is crushed by extrusion pressure to obtain powder A with a median particle size D50 = 15 μm. Powder A and a tar binder are mixed at a mass ratio of 100:10 and sintered at 1350 °C. After cooling, block B is obtained, where K90 粉料A = 1.6;

[0043] (2) Block B is crushed by impact force and friction force to obtain powder C with a median particle size D50 = 13 μm. Powder C is loaded into a graphitization furnace and graphitized to obtain the graphite anode material, where K90 粉料C = 1.15, K90 成品颗粒 = 0.99.

[0044] Example 3

[0045] This embodiment provides a graphite anode material, which is prepared by the following method:

[0046] (1) The metallurgical coke and coal are crushed by extrusion pressure to obtain powder A with a median particle size D50 = 9.0 μm. Powder A and a binder are mixed at a mass ratio of 100:50 (the binder is paraffin oil and asphalt with a mass ratio of 1:1), and sintered at 1650 °C. After cooling, block B is obtained, where K90 粉料A = 1.89;

[0047] (2) Block B is crushed by impact force and friction force to obtain powder C with a median particle size D50 = 20 μm. Powder C is loaded into a graphitization furnace and graphitized to obtain the graphite anode material, where K90 粉料C = 0.81, K90 成品颗粒 = 0.96.

[0048] Example 4

[0049] This embodiment provides a graphite anode material, which is prepared by the following method:

[0050] (1) The pitch coke is crushed by extrusion pressure to obtain powder A with a median particle size D50 = 4 μm. Powder A and an epoxy resin binder are mixed at a mass ratio of 100:35 (the binder is paraffin oil and asphalt with a mass ratio of 1:1), and sintered at 500 °C. After cooling, block B is obtained, where K90 粉料A = 1.85;

[0051] (2) The bulk material B is crushed by the action of impact force and friction force to obtain powder C, with a median particle size D50 = 6 μm. The powder C is loaded into a graphitization furnace and subjected to graphitization processing to obtain the graphite negative electrode material, where K90 粉料C = 1.8, K90 成品颗粒 = 1.87.

[0052] Example 5

[0053] The difference between this example and Example 1 is only that the mass ratio of powder A to the binder is 100:0.5, and other conditions and parameters are exactly the same as those in Example 1.

[0054] Example 6

[0055] The difference between this example and Example 1 is only that the mass ratio of powder A to the binder is 100:40, and other conditions and parameters are exactly the same as those in Example 1.

[0056] Comparative Example 1

[0057] This comparative example provides a graphite negative electrode material, which is prepared by the following method:

[0058] (1) The metallurgical coke and coal are crushed by the action of extrusion force and friction force to obtain powder A, with a mass ratio of metallurgical coke to coal of 1:1 and a median particle size D50 = 20 μm, where K90 粉料A = 1.89;

[0059] (2) The powder A is sintered and cooled at 1650 °C, and then loaded into a graphitization furnace and subjected to graphitization processing to obtain a highly vibration-compacted graphitized negative electrode material, K90 成品颗粒 = 2.76, and the SEM image of the graphite negative electrode material is as shown in Figure 4 Figure.

[0060] Comparative Example 2

[0061] This comparative example provides a graphite negative electrode material, which is prepared by the following method:

[0062] (1) The pitch coke is crushed by the action of impact force to obtain powder A, with a median particle size D50 = 4 μm, where K90 粉料A = 1.85;

[0063] (2) The powder A is sintered and cooled at 500 °C, and then loaded into a graphitization furnace and subjected to graphitization processing to obtain a highly vibration-compacted graphitized negative electrode material, K90 成品颗粒 = 2.08.

[0064] Performance test:

[0065] The graphite anode materials prepared in the examples and comparative examples were tested, and the test results are shown in Table 1:

[0066] Table 1

[0067]

[0068] As can be seen from Table 1, it can be obtained from Examples 1-4 that the tap density of the graphite anode material of the present invention can reach 1.2 g / cm 3 or more, the sphericity can reach more than 60%, and the aspect ratio can reach more than 67%.

[0069] By comparing Example 1 with Examples 5-6, it can be obtained that the mass ratio of the powder A and the binder of the present invention will affect the performance of the prepared graphite anode material. Controlling the mass ratio of the powder A and the binder at 100:(1-30) results in better performance of the prepared graphite anode material. If the addition amount of the binder is too small, the residual carbon amount is not enough to fill the particle surface and make it more rounded after secondary crushing; if the addition amount of the binder is too large, the bonding strength of the material increases, and greater mechanical force is required to break it during the secondary crushing process, which easily generates new cross-sections on the particles, resulting in an irregular morphology and affecting the tap density and sphericity of the cost.

[0070] By comparing Examples 1-4 with Comparative Examples 1-2, it can be obtained that the tap density of the graphite anode material prepared by the present invention is significantly improved, and k1 = 0.4-1.0, that is, the particle size distribution is also narrower. In terms of morphology, the examples are more regular than the comparative examples, and the sphericity and aspect ratio are higher than those of the comparative examples. As shown in the appendix Figure 2 shown, the surface of Example 1 is round, and the surface of Comparative Example 1 has more edges and corners. After the raw materials of Examples 1-4 are sintered and then secondary-crushed, the particle size distribution becomes narrower, that is, k2 = 0.4-1.0, and the morphology becomes more rounded. The tap density after secondary crushing is higher than that after primary crushing. Therefore, in the subsequent graphitization processing of the raw materials of Examples 1-4, the loading amount in the furnace will increase, thereby achieving the effect of improving production capacity and reducing costs. Therefore, the high-tap-density single particles prepared by this method not only have good performance, but also have cost advantages and are more easily accepted by the market.

[0071] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A graphite negative electrode material, characterized in that, The graphite negative electrode material includes primary particles and finished particles composed of a composite of primary particles and a binder, and the particle sizes of the primary particles and the finished particles satisfy the relational expression k1 = K90 成品颗粒 / K90 一次颗粒 = 0.3 to 1.0, where K90 = (D90 - D10) / D50; The tap density of the graphite anode material is above 1.2 g / cm 3 or more, the sphericity is above 60%, and the aspect ratio is (0.50 - 0.99):

1.

2. The graphite negative electrode material according to claim 1, characterized in that, The tap density of the graphite anode material is 1.2 to 1.4 g / cm 3 .

3. The graphite negative electrode material according to claim 1, characterized in that, The sphericity of the graphite anode material is 60-99%.

4. The graphite negative electrode material according to claim 1, characterized in that, The binder includes any one or a combination of at least two of pitch, resin, tar or paraffin oil.

5. A preparation method of the graphite negative electrode material according to any one of claims 1 - 4, characterized in that, The preparation method includes the following steps: (1) After crushing the carbon material, powder A is obtained. The powder A is mixed with the binder and sintered to obtain block B; (2) After crushing the block B obtained in step (1), powder C is obtained. The powder C is graphitized to obtain the graphite anode material.

6. The preparation method according to claim 5, characterized in that, The carbon material in step (1) includes any one or a combination of at least two of petroleum coke, needle coke, pitch coke, coke or coal.

7. The preparation method according to claim 5, characterized in that, The crushing method includes any one or a combination of at least two of extrusion, impact or friction.

8. The preparation method according to claim 5, characterized in that, The mass ratio of the powder A to the binder is 100:(1-50).

9. The preparation method according to claim 8, characterized in that, The mass ratio of the powder A to the binder is 100:(1-30).

10. The preparation method according to claim 5, characterized in that, The temperature of the sintering treatment is 400-1650 °C.

11. The preparation method according to claim 10, characterized in that, The temperature of the sintering treatment is 600-900 °C.

12. The preparation method according to claim 5, characterized in that, The median particle size D50 of the powder A is 4-20 μm.

13. The preparation method according to claim 5, characterized in that, The difference between the median particle size D50 of the powder C in step (2) and the median particle size D50 of the powder A is ≤2 μm.

14. The preparation method according to claim 5, characterized in that, The particle sizes of the powder C and the powder A satisfy the relational expression k2 = K90 粉料C / K90 粉料A = 0.3 to 1.

0.

15. A negative electrode sheet, characterized in that, The negative electrode sheet contains the graphite anode material according to any one of claims 1-4.

16. A lithium - ion battery, characterized in that, The lithium ion battery contains the negative electrode sheet according to claim 15.

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