Graphite negative electrode material for improving capacity and compaction performance and preparation method

Abstract

The invention relates to a graphite negative electrode material for improving capacity and compaction performance and a preparation method, and belongs to the technical field of lithium ion battery negative electrode materials. The graphite material is placed in rotary drum type furnace kiln equipment to be subjected to rotary temperature rise heating to 300-900 DEG C, and the rotating speed of a furnace body in the temperature rise process is 5-40 rpm; after the temperature is increased to 300-900 DEG C, a gas-phase oxidizing agent is introduced, oxidation etching is conducted on the graphite material, the flow of the gas-phase oxidizing agent is 1-20 L / min, the rotating speed of a furnace body is adjusted to be 5-100 rpm, and the constant temperature is kept for 2-7 h; and stopping introducing the gas-phase oxidant, adjusting the rotating speed of the furnace body to 5-40rpm, cooling to 100-25 DEG C, and discharging to obtain the graphite negative electrode material. The capacity and the compaction density of the graphite negative electrode material are improved, excessive increase of the specific surface area of the graphite negative electrode material is effectively inhibited, and the first effect and the cycle life are not affected.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium-ion battery anode materials, and specifically relates to a graphite anode material and its preparation method that improves capacity and compaction performance. Background Technology

[0002] In recent years, the demand for graphite anode materials in the 3C and power battery sectors has been increasing in terms of both capacity and compaction density. Applications primarily include consumer electronics, power tools, and electric vehicles. The capacity of graphite anode materials in these sectors has progressively increased from 340 to 350 to 355 to 360 mAh, while the compaction density has increased from 1.65 to 1.70 to 1.75 to 1.85. With the continuous upgrading and iteration of consumer electronics, power tools, and electric vehicles, the demand for lithium-ion battery-related products is also rising. To enhance the customer experience, the energy density requirement for lithium-ion batteries is also increasing.

[0003] To improve the energy density of lithium-ion batteries, it is essential to enhance the capacity and compaction density of the anode material. Graphite anodes are the most widely used anode material in the lithium-ion battery industry. Currently, improving the capacity and compaction density of graphite anodes mainly focuses on raw material selection, particle size distribution control, morphology modification, and graphitization processing. However, graphite anodes still exhibit numerous surface defects after graphitization. These defects not only affect the capacity utilization of the graphite anode but also the consistency of interparticle interactions, thus impacting its compaction density. Some studies have explored using oxidation etching to improve the surface defects of graphite anodes after graphitization. However, the oxidation etching process is difficult to control, leading to excessive oxidation, which damages the graphite microcrystalline structure, resulting in an increased specific surface area and reduced initial efficiency and cycle life.

[0004] Therefore, developing a precise and controllable oxidation etching method that can effectively improve the capacity and compaction density of graphite anodes while strictly suppressing the abnormal growth of their specific surface area has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a graphite anode material and preparation method that improves capacity and compaction performance. It can solve the technical problem in the prior art where the oxidation etching process is difficult to control precisely, resulting in an abnormal increase in the specific area of ​​the graphite anode material, which affects the processing performance, initial efficiency and cycle life.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] This application provides a method for preparing graphite anode materials with improved capacity and compaction properties, comprising the following steps:

[0008] S1. Graphite materials are prepared using graphite raw materials, wherein the graphite raw materials include petroleum coke, needle coke or pitch coke.

[0009] S2. The graphite material is placed in a rotary drum furnace for rotary heating, and heated from room temperature to 300-900°C at a heating rate of 0.5-10°C / min. During the heating process, the furnace rotation speed is 5-40 rpm.

[0010] S3. After heating to 300-900℃, a gaseous oxidant is introduced to oxidize and etch the graphite material. The flow rate of the gaseous oxidant is 1-20L / min, the furnace rotation speed is adjusted to 5-100rpm, and the temperature is kept constant for 1-8h.

[0011] S4. Stop the flow of the gaseous oxidant, adjust the furnace rotation speed to 5~40 rpm, and cool it down to 100~25℃ at a rate of 0.5~70℃ / min before discharging the material to obtain the graphite anode material.

[0012] Furthermore, in step S1, one or any two of the graphite raw materials are processed by crushing, shaping, granulation and graphitization processes to obtain the graphite material.

[0013] The graphite material has a particle size of Dv10 ≥1.0 μm, Dv50 3.0~17.0 μm, and Dv100 ≤70.0 μm.

[0014] Preferably, the graphite material has a particle size of Dv10 ≥ 2.0 μm, Dv50 of 5.0~15.0 μm, and Dv100 ≤ 60.0 μm.

[0015] Even more preferably, the particle size of the graphite material is Dv10≥2.0μm, Dv50 is 6.0~14.0μm, and Dv100≤50.0μm.

[0016] Preferably, in step S2, the rotary heating process includes: heating from room temperature to 300°C at a heating rate of 0.5 to 10°C / min, and then heating to 400 to 800°C at a heating rate of 2 to 10°C / min, wherein the furnace body rotation speed is 5 to 20 rpm during the heating process.

[0017] More preferably, in step S2, the rotary heating process includes: heating from room temperature to 300°C at a heating rate of 2~10°C / min, and then heating to 500~700°C at a heating rate of 5~10°C / min, with the furnace body rotating at a speed of 5~10 pm during the heating process.

[0018] Preferably, in step S3, the temperature is raised to 400-800°C, the gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 1-15 L / min, the furnace rotation speed is adjusted to 5-70 rpm, and the furnace temperature is maintained for 2-7 hours.

[0019] Further, the temperature is raised to 500-700℃, the gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 5-10L / min, the furnace rotation speed is adjusted to 10-40rpm, and the furnace temperature is maintained for 3-6 hours.

[0020] Preferably, in step S4, the gaseous oxidant is stopped, the furnace rotation speed is adjusted to 5~30 rpm, and the material is cooled to 100~25℃ at a rate of 5~70℃ / min before being discharged to prepare graphite anode material.

[0021] Further, in step S4, the gaseous oxidant is stopped, the furnace rotation speed is adjusted to 5-20 rpm, and the material is cooled to 100-25°C at a cooling rate of 30-70°C / min before being discharged to prepare the graphite anode material.

[0022] In a second aspect, this application provides a graphite anode material with improved capacity and compaction performance, wherein the graphite anode material is prepared by the preparation method described in the first aspect;

[0023] The specific capacity of the graphite anode material is increased by 1 mAh / g, and the powder compaction density is increased by 0.04 to 0.05 g / cm³.

[0024] Thirdly, this application provides a lithium-ion battery comprising the graphite anode material described in the second aspect.

[0025] 1. This invention prepares graphite materials with appropriate particle size by selecting different raw materials, and processes the graphite materials using a rotary drum furnace, so that the materials are in a continuous state of motion, ensuring the uniformity of the oxidized particles. During the processing, a suitable gaseous oxidant is introduced. Under high temperature, the gaseous oxidant plays an etching role. By optimizing and controlling parameters such as furnace rotation speed, constant temperature, constant temperature time, and oxidant flow rate, the defect structure on the surface of the graphite particles is oxidized and etched, which further improves the capacity and compaction of the graphite materials. At the same time, the controllable etching process prevents performance problems such as processing, first-time efficiency, and circulation caused by excessive increase in the specific surface area of ​​the graphite materials.

[0026] 2. This invention achieves controllable oxidation etching by optimizing process parameters (such as temperature, rotation speed, and oxidant flow rate), thereby limiting the increase in specific surface area to a small range (such as 0.3-0.4 m² / g) and avoiding material structure damage caused by excessive oxidation.

[0027] 3. The rotary drum furnace equipment and the clearly defined parameters (such as heating rate and isothermal time) used in this invention enable the preparation method to have good repeatability, controllability and feasibility for large-scale production.

[0028] 4. The graphite anode material with improved capacity and compaction performance provided by this invention effectively improves its specific capacity (by about 1 mAh / g) and powder compaction density (by 0.04-0.05 g / cm³) while maintaining the original particle size distribution and tap density, thereby increasing the battery energy density. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 These are powder compaction diagrams of Embodiment 1 and Comparative Embodiment 1 of the present invention;

[0031] Figure 2 The cyclic voltammetry curves of Embodiment 1 and Comparative Embodiment 1 of the present invention are shown below;

[0032] Figure 3 The images are XRD patterns of Implementation Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0033] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0034] Example:

[0035] This embodiment provides a preparation method for improving the capacity and compaction performance of graphite anode materials, including the following steps:

[0036] S1. Graphite materials are prepared using graphite raw materials, including petroleum coke, needle coke or pitch coke.

[0037] S2. Place the graphite material in a rotary drum furnace for rotary heating, heating it from room temperature to 300-900℃ at a heating rate of 0.5-10℃ / min, with the furnace rotating at 5-40 rpm during the heating process.

[0038] S3. After heating to 300-900℃, a gaseous oxidant is introduced to oxidize and etch the graphite material. The flow rate of the gaseous oxidant is 1-20L / min, the furnace speed is adjusted to 5-100rpm, and the temperature is kept constant for 1-8h.

[0039] S4. Stop the gas-phase oxidant, adjust the furnace rotation speed to 5~40 rpm, and cool it down to 100~25℃ at a rate of 0.5~70℃ / min before discharging the material to obtain the graphite anode material.

[0040] This invention provides a method for preparing graphite anode materials with improved capacity and compaction performance. A rotary drum furnace is used to maintain the material in a dynamic state within a certain temperature range, while a rated flow rate of gaseous oxidant is continuously introduced. This process maintains the material in this state for a specific time, achieving controllable oxidation etching of the graphite anode material. By using reasonable parameters such as rotation speed, temperature, compressed air flow rate, and time, the oxidized graphite anode material achieves improved capacity and compaction while maintaining a controllable specific surface area, ensuring that its first-efficiency and cycle life are not affected.

[0041] In step S1, one or any two of the graphite raw materials are processed by crushing, shaping, granulation and graphitization processes to obtain graphite material.

[0042] The particle size of the graphite material is Dv10≥1.0 μm, Dv50 is 3.0~17.0 μm, and Dv100≤70.0 μm.

[0043] In some embodiments, preferably, the particle size of the graphite material is Dv10≥2.0μm, Dv50 is 5.0~15.0μm, and Dv100≤60.0μm.

[0044] In some other embodiments, more preferably, the particle size of the graphite material is Dv10≥2.0μm, Dv50 is 6.0~14.0μm, and Dv100≤50.0μm.

[0045] In some embodiments, preferably, in step S2, the rotary heating process includes: heating from room temperature to 300°C at a heating rate of 0.5 to 10°C / min, and then heating at a heating rate of 2 to 10°C / min to 400 to 800°C, with the furnace body rotating at 5 to 20 rpm during the heating process.

[0046] In some other embodiments, more preferably, in step S2, the rotary heating process includes: heating from room temperature to 300°C at a heating rate of 2~10°C / min, and then heating at a heating rate of 5~10°C / min to 500~700°C, with the furnace body rotating at a speed of 5~10 pm during the heating process.

[0047] In step S2, the rotary drum furnace is either a drum furnace or a rotary kiln. By using a rotary drum furnace for processing, the material is kept in a continuous state of motion, ensuring the uniformity of the oxidized particles.

[0048] In some embodiments, preferably, in step S3, the temperature is raised to 400-800°C, a gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 1-15 L / min, the furnace rotation speed is adjusted to 5-70 rpm, and the furnace temperature is maintained for 2-7 hours.

[0049] In some other embodiments, more preferably, in step S3, the temperature is raised to 500-700°C, a gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 5-10 L / min, the furnace rotation speed is adjusted to 10-40 rpm, and the furnace temperature is maintained for 3-6 hours.

[0050] In step S3, the gaseous oxidant is one or a mixture of any two of oxygen, ozone, and air. By introducing the gaseous oxidant during the processing, it plays an etching role at high temperatures.

[0051] In some embodiments, preferably, in step S4, the gas-phase oxidant is stopped, the furnace rotation speed is adjusted to 5~30 rpm, and the material is cooled to 100~25℃ at a rate of 5~70℃ / min before being discharged to prepare graphite anode material.

[0052] In some other embodiments, more preferably, in step S4, the gaseous oxidant is stopped, the furnace rotation speed is adjusted to 5~20 rpm, and the material is cooled to 100~25°C at a cooling rate of 30~70°C / min before being discharged to prepare the graphite anode material.

[0053] Implementation Case 1:

[0054] In this embodiment, needle coke is selected as the raw material, and graphite material is obtained by crushing, shaping, granulation, deagglomeration and dispersing, graphitization and other processes. The material is a secondary particle with a final particle size of Dv10=7.3μm; Dv50=13.5μm; Dv90=22.0μm. Graphite material is fed into a rotary drum furnace and heated from room temperature (25℃) at a rate of 2-10℃ / min to 300℃. The temperature is then increased to 500-700℃ at a rate of 5-10℃ / min, with the furnace rotation speed at 5-10 rpm throughout the heating process. When the temperature reaches 500-700℃, compressed air is introduced at a flow rate of 5-10 L / min, and the furnace rotation speed is adjusted to 10-40 rpm to maintain a constant temperature for 3-6 hours. After the constant temperature stage is completed, the compressed air is turned off, the furnace rotation speed is adjusted to 5-20 rpm, and the temperature is lowered at a rate of 30-70℃ / min until the temperature reaches 100-25℃. The discharged material is the material described in Implementation Case 1.

[0055] Comparison Case 1:

[0056] The coke source batch selected in this comparative case is the same as that in Implementation Case 1, and the process and size design are also the same as in Implementation Case 1. The graphite material obtained by the processes of crushing, shaping, granulation, deagglomeration and dispersing, and graphitization is a secondary particle with a final particle size of Dv10=7.3μm; Dv50=13.5μm; Dv90=22.0μm.

[0057] Implementation Case 2:

[0058] The graphite material is obtained by using needle coke as raw material and following processes such as crushing, shaping, and graphitization. The material is a primary particle with a final particle size of Dv10=6.6μm; Dv50=12.7μm; Dv90=22.3μm. Graphite material is fed into a rotary drum furnace and heated from room temperature (25℃) at a rate of 2-10℃ / min to 300℃. The temperature is then increased to 500-700℃ at a rate of 5-10℃ / min, with the furnace rotation speed at 5-10 rpm throughout the heating process. When the temperature reaches 500-700℃, compressed air is introduced at a flow rate of 5-10 L / min, and the furnace rotation speed is adjusted to 10-40 rpm to maintain a constant temperature for 3-6 hours. After the constant temperature stage is completed, the compressed air is turned off, the furnace rotation speed is adjusted to 5-20 rpm, and the temperature is lowered at a rate of 30-70℃ / min until the temperature reaches 100-25℃. The discharged material is the material described in Implementation Case 2.

[0059] Comparison Case 2:

[0060] The coke source batch selected in this comparative case is the same as that in Implementation Case 2, and the process and size design are also the same as those in Implementation Case 2. The graphite material obtained by crushing, shaping and graphitization is a primary particle with a final particle size of Dv10=6.6μm; Dv50=12.7μm; Dv90=22.3μm.

[0061] The capacity and compaction performance of the graphite anode materials in Implementation Case 1-2 and Comparative Case 1-2 were tested, and the data obtained are shown in Table 1.

[0062] Table 1. Experimental results and test data of capacity and compaction performance of graphite anode materials.

[0063]

[0064] As shown in Table 1, comparing Implementation Case 1 and Implementation Case 2, using the above preparation method, the particle size and compaction of the material remained essentially unchanged before and after the preparation method. After the preparation method, the powder compaction increased by 0.04~0.05 g cm⁻³, and the capacity increased by approximately 1 mAh g⁻¹. The specific surface area of ​​the material increased slightly by 0.3~0.4, with minimal difference in the initial efficiency value. The moderately controllable oxidation etching of this invention can form micropores on and inside the graphite surface, increasing the diffusion path of lithium ions and making it easier for lithium ions to embed and extract between graphite layers, thereby improving capacity utilization. The moderately controllable oxidation etching of this invention can oxidize the defects existing on the surface of graphite materials after graphitization, improving the consistency of interparticle interaction forces, thereby increasing the compaction density of the material.

[0065] refer to Figure 1-3 The powder compaction diagram, cyclic voltammetry curve, and XRD pattern are for both Case 1 and Comparative Case 1. Figure 1 The powder compaction diagrams of Comparative Case 1 and Implementation Case 1 are shown. By comparing the powder compaction tests of Comparative Case 1 and Implementation Case 1, the powder compaction of Implementation Case 1 is increased by 0.04 g cm-3 compared to Comparative Case 1. Figure 2 The cyclic voltammetry curves of Comparative Case 1 and Implementation Case 1 are shown. Compared with Comparative Case 1, Implementation Case 1 has better symmetry of oxidation and reduction peaks, less battery polarization, and better capacity utilization. Figure 3 The XRD patterns of Comparative Case 1 and Implementation Case 1 are shown. The (002) diffraction peak is analyzed. The diffraction angle 2θ = 26.49° in Comparative Case 1 and 2θ = 26.51° in Implementation Case 1. This indicates that the (002) diffraction peak in Implementation Case 1 shifts to the right, and the interlayer spacing of graphite decreases, which is related to the reduction of graphite defect structure.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing graphite anode materials with improved capacity and compaction properties, characterized in that, Includes the following steps: S1. Graphite materials are prepared using graphite raw materials, wherein the graphite raw materials include petroleum coke, needle coke or pitch coke. S2. The graphite material is placed in a rotary drum furnace for rotary heating, and heated from room temperature to 300-900°C at a heating rate of 0.5-10°C / min. During the heating process, the furnace rotation speed is 5-40 rpm. S3. After heating to 300-900℃, a gaseous oxidant is introduced to oxidize and etch the graphite material. The flow rate of the gaseous oxidant is 1-20L / min, the furnace rotation speed is adjusted to 5-100rpm, and the temperature is kept constant for 1-8h. S4. Stop the flow of the gaseous oxidant, adjust the furnace rotation speed to 5~40 rpm, and cool it down to 100~25℃ at a rate of 0.5~70℃ / min before discharging the material to obtain the graphite anode material.

2. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 1, characterized in that, Step S1 includes processing one or any two of the graphite raw materials through crushing, shaping, granulation and graphitization processes to obtain the graphite material; The graphite material has a particle size of Dv10 ≥ 1.0 μm, Dv50 of 3.0~17.0 μm, and Dv100 ≤ 70.0 μm.

3. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 1, characterized in that, In step S2, the rotary heating process includes: The temperature is increased from room temperature to 300°C at a heating rate of 0.5–10°C / min, and then increased to 400–800°C at a heating rate of 2–10°C / min. During the heating process, the furnace body rotation speed is 5–20 rpm.

4. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 1, characterized in that, In step S3, the temperature is raised to 400-800℃, the gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 1-15L / min, the furnace rotation speed is adjusted to 5-70rpm, and the furnace temperature is maintained for 2-7h. The gaseous oxidant is one or any two of oxygen, ozone, and air.

5. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 1, characterized in that, In step S4, the gaseous oxidant is stopped, the furnace rotation speed is adjusted to 5~30 rpm, and the material is cooled to 100~25℃ at a rate of 5~70℃ / min before being discharged to obtain the graphite anode material.

6. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 3, characterized in that, In step S2, the rotary heating process includes: heating from room temperature to 300°C at a heating rate of 2~10°C / min, and then heating to 500~700°C at a heating rate of 5~10°C / min, during which the furnace body rotation speed is 5~10pm.

7. The preparation method for improving the capacity and compaction performance of graphite anode materials according to claim 4, characterized in that, In step S3, the temperature is raised to 500-700°C, the gaseous oxidant is introduced, the flow rate of the gaseous oxidant is 5-10 L / min, the furnace rotation speed is adjusted to 10-40 rpm, and the furnace temperature is maintained for 3-6 hours.

8. A method for preparing graphite anode materials with improved capacity and compaction properties according to any one of claims 5, characterized in that, In step S4, the gaseous oxidant is stopped, the furnace rotation speed is adjusted to 5~20 rpm, and the material is cooled to 100~25℃ at a cooling rate of 30~70℃ / min before being discharged to prepare graphite anode material.

9. A graphite anode material with improved capacity and compaction properties, characterized in that... The graphite anode material is prepared by the preparation method described in any one of claims 1-8; The specific capacity of the graphite anode material is increased by 1 mAh / g, and the powder compaction density is increased by 0.04 to 0.05 g / cm³.

10. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the graphite anode material as described in claim 9.

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