Preparation method of artificial graphite negative electrode material, negative electrode and battery

Abstract

The application provides a preparation method of artificial graphite negative electrode material, a negative electrode and a battery, and the method comprises the following steps: drying treatment is performed on artificial graphite to obtain dry material; crushing treatment is performed on the dry material to obtain powder; shaping treatment is performed on the powder; the shaped powder is mixed with pitch, and granulation treatment is performed on the mixture in a roller furnace to obtain granular material; scattering treatment is performed on the granular material, and shaping treatment is performed on the granular material after the scattering treatment; and graphitization treatment is performed on the shaped granular material. The application can improve the working performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for preparing an artificial graphite anode material, an anode, and a battery. Background Technology

[0002] Graphite, as the primary negative electrode material for lithium-ion batteries, can be broadly categorized into natural graphite, artificial graphite, and mesophase carbon microspheres. Among these, artificial graphite is widely used in lithium-ion batteries due to its excellent electrolyte compatibility and superior cycle stability.

[0003] However, artificial graphite manufactured using conventional processes generally has a low capacity. To improve its capacity, anisotropic needle coke is typically used as a precursor, and the following processing techniques are employed: (i) ultra-high temperature graphitization; (ii) catalytic graphitization of the artificial graphite precursor using a catalyst. While the capacity of the artificial graphite obtained after these precursor selection and graphitization steps is significantly improved, its higher degree of graphitization results in a more ordered internal structure, thus sacrificing some of the original advantages of artificial graphite, such as good charge-discharge structural stability and a high lithium-ion diffusion coefficient.

[0004] Therefore, how to improve the performance of batteries when artificial graphite is used as the negative electrode material has become an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned issues, the present invention provides a method for preparing artificial graphite anode materials, an anode, and a battery. By performing a shaping process on the material before and after granulation, the tap density of the artificial graphite anode material can be effectively increased, thereby improving the performance of the corresponding battery.

[0006] In a first aspect, the present invention provides a method for preparing an artificial graphite anode material, the method comprising:

[0007] The artificial graphite is dried to obtain the dry material;

[0008] The dry material is crushed to obtain powder.

[0009] The powder is shaped.

[0010] The shaped powder is mixed with asphalt and then granulated in a rotary kiln to obtain granular material.

[0011] The granular material is broken down and then shaped.

[0012] The shaped granular material is then graphitized.

[0013] Optionally, the step of crushing the dry material to obtain powder includes:

[0014] The dry material is coarsely crushed to obtain coarsely crushed material;

[0015] The coarse materials are crushed to obtain powder.

[0016] The coarse crushed material has a particle size of less than 5 mm, and the powder contains 50% artificial graphite with a particle size of 10.5 ± 1.0 micrometers. The tapped density of the powder is greater than or equal to 0.58 g / cm³. 3 .

[0017] Optionally, before the step of mixing the shaped powder with asphalt and granulating it in a rotary kiln to obtain granular material, the method further includes:

[0018] The asphalt is crushed.

[0019] In the pulverized asphalt, asphalt with a particle size of 3.5±1.5μm accounts for 50%;

[0020] In the granulated material obtained after granulation, the mass ratio of asphalt to artificial graphite ranges from 3% to 20%, and granules with a particle size of 20.0 ± 4.0 micrometers account for 50%; the tapped density of the granules is greater than or equal to 0.45 g / cm³. 3 The volatile matter content of particulate materials is less than 7%.

[0021] Optionally, after the step of graphitizing the shaped particulate material, the method further includes:

[0022] The graphitized granular material is demagnetized and screened.

[0023] Optionally, the particle size of the demagnetized and screened granular material is 15.0 ± 1.5 micrometers, accounting for 50%, and the tapped density of the demagnetized and screened granular material is 1.0 ± 0.1 g / cm³. 3 The specific surface area of ​​the granular material after demagnetization and screening is 2.0 ± 0.4 m². 2 / g.

[0024] Optionally, in the graphitized particulate material, particles with a diameter of 15.0 ± 2.0 micrometers account for 50%, and the tap density of the graphitized particulate material is greater than or equal to 0.95 g / cm³. 3 The specific surface area of ​​the graphitized particulate material is less than or equal to 2.5 m². 2 / g.

[0025] Optionally, the particle size of the dispersed granular material is less than 8 mm.

[0026] Optionally, in the shaped granular material, 50% of the granular material has a particle size of 17.0 ± 2.0 micrometers, and the tapped density of the shaped granular material is greater than or equal to 0.55 g / cm³. 3 The specific surface area of ​​the shaped granular material is less than or equal to 2.0 m². 2 / g, the loose density of the shaped granular material is 0.35±0.1g / cm³. 3 .

[0027] Secondly, the present invention provides a negative electrode, which is obtained by any of the methods described above.

[0028] Thirdly, the present invention provides a battery, wherein the negative electrode of the battery is obtained by any of the methods described above.

[0029] The method for preparing artificial graphite anode material, the anode, and the battery provided in this invention improves the tap density of the powder by shaping the powder particles to make them smoother. Simultaneously, the artificial graphite anode material granulated with asphalt is protected in terms of structure and surface state during cycling, enhancing cycle stability. The secondary particles formed by granulation can increase the number of Li+ insertion / extraction channels in the crystal lattice, further improving the rate performance and low-temperature performance of the anode material. Furthermore, after granulation, further dispersing and shaping of the granulated material within the chamber can further increase the tap density, facilitating subsequent homogenization. It also crushes granulated agglomerates, which is beneficial for subsequent graphitization, thereby improving the battery's capacity, performance, and lifespan. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart illustrating a method for preparing an artificial graphite anode material according to an embodiment of this application.

[0032] Figure 2 This is a scanning electron microscope image of granulated particulate material according to an embodiment of this application. Detailed Implementation

[0033] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0034] 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0036] The raw material for the artificial graphite involved in this invention is not graphite ore, but coke, including petroleum coke and needle coke. Artificial graphite is produced through four main processes: crushing, granulation, graphitization, and sieving of the raw materials and binders. These four processes are further subdivided into more than a dozen steps, with a generally consistent workflow, which will not be elaborated upon in the embodiments of this invention. It should also be noted that the granulation process generally determines the size, distribution, and morphology of the artificial graphite particles, affecting multiple performance indicators of the anode material. Generally speaking, smaller artificial graphite particles result in better rate performance and cycle life, but worse initial efficiency and compaction density, and vice versa. A reasonable particle size distribution (mixing large and small particles) can improve the specific capacity of the anode. Simultaneously, the morphology of the artificial graphite particles also has a significant impact on the battery's rate performance and low-temperature performance.

[0037] In addition to graphitization, graphitization is another crucial step in the preparation of artificial graphite. This step transforms the thermodynamically unstable "two-dimensional disordered overlapping" arrangement of carbon atoms into a "three-dimensional ordered overlapping" arrangement. As the graphitization temperature increases, the disordered carbon atoms gradually transform from a random, irregular arrangement into a regularly arranged hexagonal planar network structure, exhibiting a layered arrangement. That is, the structure changes from a random layer structure to an ordered graphite crystal structure. Starting from 2200℃, a relatively complete layered structure is basically formed, transforming coke into graphitized carbon. Furthermore, with continued temperature increases, the layered structure becomes more complete, and the degree of graphitization continuously improves.

[0038] In a first aspect, one embodiment of the present invention provides a method for preparing an artificial graphite anode material, see [link to previous section]. Figure 1 The method includes steps S101 to S106:

[0039] Step S101: Dry the artificial graphite to obtain dry material.

[0040] Step S102: Crush the dry material to obtain powder.

[0041] In one optional embodiment, the step of crushing the dry material to obtain powder includes:

[0042] The dry material is coarsely crushed to obtain coarsely crushed material; the coarsely crushed material is then pulverized to obtain powder.

[0043] The coarse crushed material has a particle size of less than 5 mm, and the powder contains 50% artificial graphite with a particle size of 10.5 ± 1.0 micrometers. The tapped density of the powder is greater than or equal to 0.58 g / cm³. 3 .

[0044] Step S103: Shape the powder.

[0045] Step S104: The shaped powder is mixed with asphalt and granulated in a rotary kiln to obtain granular material. Figure 2 .

[0046] In an optional embodiment, before the step of mixing the shaped powder with asphalt and granulating it in a rotary kiln to obtain granular material, the method further includes:

[0047] The asphalt is crushed.

[0048] In the pulverized asphalt, 50% of the asphalt has a particle size of 3.5 ± 1.5 μm. In the granulated material obtained after granulation, the mass ratio of asphalt to artificial graphite ranges from 3% to 20%, and 50% of the granules have a particle size of 20.0 ± 4.0 μm; the tapped density of the granules is greater than or equal to 0.45 g / cm³. 3 The volatile matter content of particulate materials is less than 7%.

[0049] Step S105: Disperse the granular material and reshape the dispersed granular material.

[0050] In one alternative embodiment, the particle size of the dispersed particulate material is less than 8 mm.

[0051] In one optional embodiment, particles with a diameter of 17.0 ± 2.0 micrometers account for 50% of the shaped granular material, and the tapped density of the shaped granular material is greater than or equal to 0.55 g / cm³. 3 The specific surface area of ​​the shaped granular material is less than or equal to 2.0 m². 2 / g, the loose density of the shaped granular material is 0.35±0.1g / cm³. 3 .

[0052] Step S106: Graphitize the shaped granular material.

[0053] In an optional embodiment, after the step of graphitizing the shaped particulate material, the method further includes:

[0054] The graphitized granular material is demagnetized and screened.

[0055] Among them, 50% of the granular material after demagnetization and sieving has a particle size of 15.0±1.5 micrometers, and the tapped density of the granular material after demagnetization and sieving is 1.0±0.1 g / cm³. 3 The specific surface area of ​​the granular material after demagnetization and screening is 2.0 ± 0.4 m². 2 / g.

[0056] In one optional embodiment, particles with a diameter of 15.0 ± 2.0 micrometers account for 50% of the graphitized particulate material, and the tap density of the graphitized particulate material is greater than or equal to 0.95 g / cm³. 3 The specific surface area of ​​the graphitized particulate material is less than or equal to 2.5 m². 2 / g.

[0057] The method for preparing artificial graphite anode material, the anode, and the battery provided in this embodiment improves the tap density of the powder by shaping the powder particles to make them smoother. Simultaneously, the artificial graphite anode material granulated with asphalt is protected in terms of structure and surface state during cycling, enhancing cycle stability. The secondary particles formed by granulation can increase the number of Li+ insertion / extraction channels in the crystal lattice, further improving the rate performance and low-temperature performance of the anode material. Furthermore, after granulation, further dispersing and shaping of the granulated material within the chamber can further increase the tap density, facilitating subsequent homogenization. It also crushes the granulated agglomerates, which is beneficial for subsequent graphitization, thereby improving the battery's capacity, performance, and lifespan.

[0058] Secondly, an embodiment of the present invention provides a method for preparing an artificial graphite anode material. Based on the first aspect, in the method for preparing the artificial graphite anode material provided in this embodiment, the artificial graphite needs to undergo drying and dehydration, coarse crushing, pulverizing, shaping, coating, granulation, dispersing, shaping, graphitization, and demagnetization sieving treatments in sequence. Specifically:

[0059] During the drying and dehydration process, the temperature of the heat transfer oil in the kneader is controlled at 205.0±5.0℃; the drying and dehydration time is controlled at 60.0±30.0min; and the moisture content of the needle coke after drying is required to be ≤2.5%.

[0060] In the coarse crushing process, the manganese steel screen of the hammer crusher is selected with a specification of 5.0mm; in the process monitoring, 200 grams of material passing through the 5.0mm standard screen and being screened on the vibrating screen for 3 minutes has a passing rate of 100%.

[0061] In the pulverization process, the impact mill parameters of the air jet pulverizer used for dry material pulverization are set as follows: feed frequency 15.0±5.0Hz; main machine frequency 40.0±10.0Hz; classifier frequency 30.0±10.0Hz; induced draft fan frequency 45.0±5.0Hz;

[0062] The 30B pulverizer used for asphalt pulverization has a screen aperture of 0.6mm and a feeding frequency of 20.0Hz. The coarse crushing feed valve of the air jet pulverizer used in this pulverizer has a frequency of 20.0Hz, the high-pressure blower has a frequency of 40.0Hz, and the pulverizing pressure is 0.7±0.1MPa.

[0063] The particle size distribution of the needle coke before calcination, after being pulverized, is as follows: particle size 3.5μm – greater than D10; particle size 10.5±1.0μm – D50; particle size 25.0μm – less than D90; and the tap density of the powder is ≥0.58g / cm³. 3 The particle size distribution of the asphalt after pulverization is: particle size 3.5±1.5μm——D50.

[0064] In the shaping process, the main frequency of the airflow shaping and classifying machine is 40.0±10.0Hz; the classifier frequency is 45.0±10.0Hz; the induced draft fan frequency is 18.0±2.0Hz; the feeding time is 110.0S; the feeding frequency is 70.0±10.0Hz; the production time is 180±60.0S; the working time of the finished product upper valve is 80.0S; and the working time of the finished product lower valve is 80.0S.

[0065] In the coating process, the asphalt content is 3-20%, preferably 8-10%; the parameters of the VC mixer (also known as a vacuum mixer) are set as follows: main unit frequency 45.0Hz; mixing time 30.0min; star-shaped discharge valve frequency 13.0±2.0Hz.

[0066] In the granulation process, the rotary drum furnace was loaded with 350.0±5.0 kg at a rotation speed of 15.5 Hz. The nitrogen and oxygen content inside the furnace was ≤50.0 ppm, the nitrogen pressure was 0.05±0.01 MPa, and the nitrogen flow rate was 5.0±1.0 L / min. Both the furnace head and tail screens used 150 mesh. The furnace temperature profile was as follows: the first stage involved heating from room temperature to 300.0℃ in 2.0 hours; the second stage involved continuous heating to 350℃ in 1.5 hours; the third stage involved continuous heating to 550℃ in 2.0 hours; the fourth stage involved holding at 550.0±10.0℃ for 2.0 hours; and finally, the material was discharged after air cooling to 45.0±15.0℃.

[0067] The particle size distribution of the granulated material after granulation is as follows: particle size 8.0 μm – greater than D10; particle size 20.0 ± 4.0 μm – D50; particle size 45.0 μm – less than D90; the tap density of the granulated material after granulation is ≥0.45 g / cm³. 3 The volatile matter content of the granulated material after granulation is <7.0%.

[0068] In the dispersing process, the screen size of the dispersing machine is 8.0mm.

[0069] During the shaping process, the parameters of the shaping machine are set as follows: main machine frequency 25.0±10.0Hz; classifier (auxiliary machine) frequency 45.0±10.0Hz; fan frequency 18.0±2.0Hz; feeding time 110.0s; shaping time 120.0±60.0s; finished product upper valve working time 30.0s; finished product lower valve working time 60.0s; feeding frequency 70.0±10.0Hz.

[0070] The particle size distribution of the shaped granular material is as follows: particle size 7.5μm – greater than D10; particle size 17.0±2.0μm – D50; particle size 35.0μm – less than D90; and the tapped density of the shaped granular material is ≥0.55g / cm³. 3 The moisture content of the shaped granular material is <1.0%; the ash content of the shaped granular material is <1.0%; the volatile matter content of the shaped granular material is <7.0%; and the specific surface area of ​​the shaped granular material is ≤2.0 m². 2 / g; the loose bulk density of the shaped granular material is 0.35±0.1g / cm³. 3 .

[0071] In the graphitization process, the highest temperature of the graphitization furnace is ≥3000.0℃, and the holding time at the highest temperature is 10.0±1.0h; the particle size distribution of the graphitized particulate material is: particle size 15.0±2.0μm—D50; the specific surface area of ​​the graphitized particulate material is ≤2.5m². 2 / g; Ash content of graphitized granular material <0.1%; Tap density of graphitized granular material ≥0.95g / cm³ 3 The magnetic content (Cr+Fe+Zn+Co+Ni) of the graphitized particulate material is ≤0.8ppm; the degree of graphitization of the graphitized particulate material is ≥92.0%.

[0072] In the demagnetization screening process, the mixing time of the mixer is 2.0h, and the screen is a double-layer 325 mesh screen; the sieving feeding frequency is 10.0±5.0Hz; the demagnetization intensity of the demagnetizer is 100% (12000.0GS), the feeding cycle is 10.0min, the passing time is 60.0s, the demagnetization time is 60.0s, and the oil temperature circulation time is 30.0min.

[0073] The particle size distribution of the granular material after demagnetization and sieving is as follows: particle size 6.5μm – greater than D10; particle size 15.0±1.5μm – D50; particle size 35.0μm – less than D90; the maximum particle size in the granular material after demagnetization and sieving is no greater than 60.0μm; the tap density of the granular material after demagnetization and sieving is 1.0±0.1g / cm³. 3 The specific surface area of ​​the granular material after demagnetization and screening is 2.0 ± 0.4 m². 2 / g; Fe≤30.0ppm, Al≤5.0ppm, Cu≤5.0ppm, Cr≤5.0ppm, Ni≤5.0ppm, and magnetic matter (Cr+Fe+Zn+Co+Ni)≤0.5ppm in the demagnetized granular material; fixed carbon content of the demagnetized granular material >99.9%; moisture content of the demagnetized granular material <0.1%; ash content of the demagnetized granular material <0.08%; initial capacity of the demagnetized granular material ≥350.0mAh / g; initial efficiency of the demagnetized granular material ≥92.0%.

[0074] The battery prepared using the artificial graphite anode material obtained in this embodiment was tested, and the following data were obtained, as shown in Table 1:

[0075] Table 1

[0076]

[0077] The first charge is the first capacitance, and the first efficiency is obtained by dividing the first charge by the first discharge.

[0078] It should be noted that small particles in artificial graphite anode materials have a large specific surface area, resulting in more lithium-ion migration channels, shorter paths, and better rate performance, while large particles have high compaction density and large capacity. The method provided in this embodiment combines the advantages of both large and small particles through a secondary particle processing method involving shaping, granulation, and reshaping, achieving an artificial graphite anode material with high capacity and good rate performance. Furthermore, the secondary particles formed by the granulation process increase the isotropy of the anode material, which also affects the battery's initial coulombic efficiency and rate performance.

[0079] Thirdly, the present invention provides a negative electrode, which is obtained by the method described in the first or second aspect.

[0080] Fourthly, the present invention provides a battery, wherein the negative electrode of the battery is obtained by the method described in the first or second aspect.

[0081] In the description of this specification, the references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing an artificial graphite anode material, characterized in that, The method includes: The artificial graphite is dried to obtain the dry material; The dry material is crushed to obtain a powder; the powder contains 50% of artificial graphite with a particle size of 10.5±1.0 microns, and the tap density of the powder is greater than or equal to 0.58 g / cm 3 ; The powder is then shaped. The shaped powder is mixed with asphalt and granulated in a rotary kiln to obtain granular material. In the shaped granular material, particles with a diameter of 17.0 ± 2.0 micrometers account for 50%, and the tapped density of the shaped granular material is greater than or equal to 0.55 g / cm³. 3 The specific surface area of ​​the shaped particulate material is less than or equal to 2.0 m². 2 / g; The granular material is broken down and then shaped. The shaped particulate material is then subjected to graphitization treatment.

2. The method according to claim 1, characterized in that, The step of crushing the dry material to obtain powder includes: The dry material is coarsely crushed to obtain coarsely crushed material; The coarse material is crushed to obtain the powder. The particle size of the coarse crushed material is less than 5 mm.

3. The method according to claim 1, characterized in that, Before the step of mixing the shaped powder with asphalt and granulating it in a rotary kiln to obtain granular material, the method further includes: The asphalt is pulverized. In the pulverized asphalt, asphalt with a particle size of 3.5 ± 1.5 μm accounts for 50%; In the granulated material obtained after granulation, the mass ratio of asphalt to artificial graphite ranges from 3% to 20%, and the granules with a particle size of 20.0 ± 4.0 micrometers account for 50%; the tapped density of the granules is greater than or equal to 0.45 g / cm³. 3 The volatile matter content of the particulate material is less than 7%.

4. The method according to claim 1, characterized in that, After the step of graphitizing the shaped particulate material, the method further includes: The graphitized particulate material is then demagnetized and screened.

5. The method according to claim 4, characterized in that, After demagnetization and sieving, 50% of the particulate material has a particle size of 15.0 ± 1.5 micrometers, and the tapped density of the particulate material after demagnetization and sieving is 1.0 ± 0.1 g / cm³. 3 The specific surface area of ​​the particulate material after demagnetization and sieving is 2.0 ± 0.4 m². 2 / g.

6. The method according to claim 1, characterized in that, In the graphitized particulate material, particles with a diameter of 15.0 ± 2.0 micrometers account for 50%, and the tap density of the graphitized particulate material is greater than or equal to 0.95 g / cm³. 3 The specific surface area of ​​the graphitized particulate material is less than or equal to 2.5 m². 2 / g.

7. The method according to claim 1, characterized in that, The particle size of the granular material after the dispersion treatment is less than 8 mm.

8. The method according to claim 1, characterized in that, The loose bulk density of the shaped granular material is 0.35 ± 0.1 g / cm³. 3 .

9. A negative electrode, characterized in that, The negative electrode is obtained by the method described in any one of claims 1 to 8.

10. A battery, characterized in that, The negative electrode of the battery is obtained by the method described in any one of claims 1 to 8.

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