Preparation method of graphite blended hard, negative active material and battery
By using an embedded composite material formed by layering graphite and hard carbon, the problem of uneven reaction and lithium plating in graphite anode materials during fast charging was solved, resulting in a lithium-ion battery anode material with high energy density and high rate performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGXI GANFENG BATTERY TECH
- Filing Date
- 2024-11-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing graphite anode materials exhibit uneven reaction current and irreversible lithium plating during fast charging, resulting in insufficient safety performance and energy density of lithium-ion batteries.
A graphite-hard carbon-graphite layered composite material was prepared by using a method of stacking graphite and hard carbon. The high disorder and large interlayer spacing of hard carbon were used to improve the migration space of lithium ions, and a stable composite structure was formed by carbonization treatment.
It improves the fast-charging and safety performance of lithium-ion batteries, enhances the kinetic properties and energy density of materials, and avoids uneven reactions and lithium plating.
Smart Images
Figure CN122117752A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery technology, and in particular to a method for preparing graphite-doped hard carbon. Background Technology
[0002] With the continuous development of power lithium-ion batteries, the demand for lithium-ion batteries with fast charging and discharging capabilities and high energy density is becoming increasingly strong. Currently, graphite is still the most widely used anode material in the entire lithium-ion battery industry, accounting for over 99% of the anode market share. Although the technology and market for graphite anodes in lithium-ion batteries are very mature, many problems remain to be solved in practical applications. For example, although graphite anodes have high energy density, they exhibit uneven reaction current and irreversible lithium plating during fast charging. In contrast, hard carbon, although having lower energy density, has a higher average voltage and higher disorder, exhibiting better rate performance. Furthermore, the excellent kinetic properties of hard carbon can accelerate lithium-ion insertion and extraction, reducing the risk of lithium plating and thus improving the safety performance of lithium-ion batteries. To improve the lithium plating phenomenon of graphite, researchers have begun to explore the use of hard carbon mixed with graphite to prepare a novel battery anode material. However, how to use appropriate methods to prepare anode materials with high energy density and high rate performance has become a key problem that urgently needs to be solved. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing a negative electrode material with high energy density and high rate performance, a negative electrode sheet, and a battery, aiming to solve the technical problems of poor fast charging performance and irreversible lithium plating of existing graphite negative electrode materials.
[0004] This invention provides a method for preparing graphite-blended hard carbon, characterized by the following steps: S1: Preparing hard carbon precursor powder: first, the hard carbon precursor is pulverized into micron-sized particles, then the hard carbon precursor particles are cleaned with anhydrous ethanol and then dried; S2: The hard carbon precursor powder obtained in step S1 is pressed into thin sheets using a tablet press and a first pressure is continuously applied; S3: The hard carbon sheets prepared in step S2 are used as sandwich layers, and graphite blocks-hard carbon layers-graphite blocks are stacked layer by layer in the order of graphite blocks-hard carbon layers-graphite blocks; S4: A second pressure is applied to the stacked materials prepared in step S3; S5: The materials prepared in step S4 are carbonized under the protection of N2 to obtain a graphite-hard carbon-graphite layered composite material. S6: The material carbonized in step S5 is crushed to obtain powder particles.
[0005] Preferably, the hard carbon precursor is any one of asphalt, biomass, and resin.
[0006] Preferably, the particle size of the hard carbon precursor after pulverization in step S1 is 50μm-70μm.
[0007] Preferably, the thickness of the precursor sheet in step S2 is 200μm-500μm.
[0008] Preferably, the first pressure range of step S2 is 10 MPa - 50 MPa, and the time for applying the first pressure is 10 min - 15 min.
[0009] Preferably, in step S3, the thickness of the graphite block is 1 mm to 2 mm, and the number of layers of the graphite block and the hard carbon precursor stacked together is 3 to 7.
[0010] Preferably, the second pressure applied in step S4 is 10 kPa - 15 kPa.
[0011] Preferably, in step S5, the carbonization temperature is 800℃-1400℃ and the carbonization time is 10-24h.
[0012] Another aspect of the present invention provides a negative electrode active material prepared by the method described above.
[0013] Another aspect of the present invention provides a battery comprising the above-described negative electrode active material.
[0014] The method for preparing graphite-doped hard carbon according to the present invention yields a negative electrode material. Due to the large interlayer spacing and higher degree of disorder of hard carbon, this material is suitable for Li… + Providing sufficient migration space, the composite material improves Li compared to pure graphite. + The rate of diffusion. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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.
[0016] Figure 1 This is a flowchart of the preparation method of graphite-blended hard carbon according to the present invention; Figure 2 This is a schematic diagram of the structure of the material prepared by the method for preparing graphite-blended hard carbon according to the present invention. Detailed Implementation
[0017] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Example 1
[0018] The preparation method of graphite-doped hard carbon in this embodiment is roughly as follows: Figure 1 The steps are as follows: First, cotton is used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities; then it is placed in a vacuum drying oven for overnight drying. The dried cotton is then pressed into 300μm sheets using a sheet press and continuously pressurized at 30MPa for 12 minutes to ensure sufficient contact between the fibers in the cotton. The 300μm cotton sheets are used as a sandwich layer and stacked with 1.5mm graphite blocks in a graphite block-cotton sheet-graphite block sequence, for a total of 7 layers. Three pieces of corundum are placed on the stacked material to achieve a pressure of 10kPa, and then it is placed in a tube furnace and carbonized at 1000℃ for 16 hours under N2 protection to obtain a graphite-hard carbon-graphite layered composite material. Finally, the carbonized material is pulverized into 15μm particles to obtain a lithium-ion battery anode material with high specific capacity and high rate performance. Example 2
[0019] Coconut shells were used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities. They were then dried overnight in a vacuum drying oven. The dried coconut shells were pressed into 500 μm sheets using a sheet press and subjected to a pressure of 60 MPa for 15 minutes to ensure sufficient contact between the fibers. The 500 μm coconut shell sheets were used as a core layer and stacked with 2 mm graphite blocks in a graphite-cotton sheet-graphite-block sequence, for a total of three layers. Five corundum stones were placed on top of the stacked material to achieve a pressure of 15 kPa. The material was then placed in a tube furnace and carbonized at 800°C for 24 hours under nitrogen protection to obtain a graphite-hard carbon-graphite layered composite material. Finally, the carbonized material was pulverized into 30 μm particles to obtain a lithium-ion battery anode material with high specific capacity and high rate performance. Example 3
[0020] Bamboo was used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities. It was then dried overnight in a vacuum drying oven. The dried bamboo was pressed into 400 μm sheets using a sheet press and subjected to a pressure of 40 MPa for 12 minutes to ensure sufficient contact between the bamboo fibers. A 500 μm bamboo sheet was used as a core layer and stacked with 2 mm graphite blocks in a graphite-cotton sheet-graphite-block sequence, for a total of 5 layers. Three corundum stones were placed on top of the stacked material to achieve a pressure of 10 kPa. The material was then placed in a tube furnace and carbonized at 1300℃ for 12 hours under nitrogen protection to obtain a graphite-hard carbon-graphite layered composite material. Finally, the carbonized material was pulverized into 20 μm particles to obtain a lithium-ion battery anode material with high specific capacity and high rate performance.
[0021] Comparative Example 1 Cotton was used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities. It was then dried overnight in a vacuum drying oven. The dried cotton was pressed into 300 μm sheets using a blister press and subjected to a pressure of 30 MPa for 12 minutes to ensure sufficient contact between the fibers. Three corundum stones were then placed on the sheets to achieve a pressure of 10 kPa before the sheets were placed in a tube furnace and carbonized at 1000°C for 16 hours under nitrogen protection to obtain hard carbon. Finally, the carbonized hard carbon was pulverized into 15 μm particles and mixed with graphite in a 1:1 ratio to obtain a graphite-doped hard carbon composite material.
[0022] Comparative Example 2 Coconut shells were used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities. They were then dried overnight in a vacuum drying oven. The dried coconut shells were pressed into 500 μm sheets using a tablet press and subjected to a pressure of 60 MPa for 15 minutes to ensure sufficient contact between the fibers. Five corundum stones were then placed on the sheets to achieve a pressure of 15 kPa before the sheets were placed in a tube furnace and carbonized at 800°C for 24 hours under nitrogen protection to obtain hard carbon. Finally, the carbonized hard carbon was pulverized into 30 μm particles and mixed with graphite in a 1:1 ratio to obtain a graphite-doped hard carbon composite material.
[0023] Comparative Example 3 Bamboo was used as a precursor for hard carbon and cleaned with anhydrous ethanol in an ultrasonic cleaner for 30 minutes to remove impurities. It was then dried overnight in a vacuum drying oven. The dried bamboo was pressed into 400 μm sheets using a tablet press and subjected to a pressure of 40 MPa for 12 minutes to ensure sufficient contact between the bamboo fibers. Three corundum stones were then placed on the sheets to achieve a pressure of 10 kPa before placing them in a tube furnace and carbonizing at 1300℃ for 12 hours under nitrogen protection to obtain hard carbon. Finally, the carbonized hard carbon was pulverized into 20 μm particles and mixed with graphite in a 1:1 ratio to obtain a graphite-doped hard carbon composite material.
[0024] The negative electrode materials obtained in the examples and comparative examples were used as active materials to fabricate lithium-ion half-cells. Negative electrode sheets were prepared using the same amounts of active material, binder, and conductive agent, with a weight percentage of 94%:3%:3% for the active material, conductive agent, and binder. Coin cell half-cells were assembled and subjected to charge-discharge capacity retention tests. The test results are shown in Table 1.
[0025] Experimental protocol Battery capacity retention rate at 2C (%) Battery capacity retention rate (%) after 50 cycles at 0.5C Example 1 90.3 99.1 Example 2 92.5 98.3 Example 3 91.7 98.7 Comparative Example 1 83.7 94.2 Comparative Example 2 81.9 86.3 Comparative Example 3 79.4 92.7 like Figure 2 As shown, the negative electrode material of this invention incorporates hard carbon intercalated between graphite layers. This layer-by-layer intercalation structure expands the interlayer spacing of the composite material, thereby reducing the resistance to lithium ion insertion and extraction, improving its kinetic performance, and achieving fast-charging performance. This addresses the problem of poor fast-charging performance of graphite as a negative electrode material for lithium-ion batteries. The graphite-hard carbon composite material prepared using the method of this invention exhibits a larger interlayer spacing and higher disorder, making it suitable for Li-ion batteries. + Providing sufficient migration space, the composite material improves Li compared to pure graphite. + The diffusion rate; the negative electrode material prepared by the method of the present invention achieves uniform mixing of graphite and hard carbon during the synthesis process, avoiding the uneven phenomenon that occurs when directly using physical mixing.
[0026] The composite material prepared by the method of this invention can improve the kinetic performance of the material, maintain structural stability, and increase active sites, making it a novel anode material that meets the requirements of high energy density and high rate performance.
[0027] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing graphite-blended hard carbon, characterized in that, Includes the following steps: S1: Preparation of hard carbon precursor powder: First, the hard carbon precursor is crushed into micron-sized particles, then the hard carbon precursor particles are cleaned with anhydrous ethanol and then dried. S2: The hard carbon precursor powder obtained in step S1 is pressed into thin sheets by a tablet press and a first pressure is continuously applied. S3: The hard carbon sheet prepared in step S2 is used as a sandwich layer, and the layers are stacked in the order of graphite block-hard carbon layer-graphite block; S4: Apply a second pressure to the layered material prepared in step S3; S5: Carbonize the material prepared in step S4 under the protection of N2 to obtain a graphite-hard carbon-graphite layer-by-layer composite material. S6: The material carbonized in step S5 is crushed to obtain powder particles.
2. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, The hard carbon precursor can be any one of asphalt, biomass, or resin.
3. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, The particle size of the hard carbon precursor after pulverization in step S1 is 50μm-70μm.
4. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, The thickness of the precursor sheet in step S2 is 200μm-500μm.
5. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, The first pressure range of step S2 is 10 MPa - 50 MPa, and the time for applying the first pressure is 10 min - 15 min.
6. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, In step S3, the graphite block has a thickness of 1 mm to 2 mm, and the graphite block and the hard carbon precursor are stacked in 3 to 7 layers.
7. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, The second pressure applied in step S4 is 10 kPa - 15 kPa.
8. The method for preparing graphite-blended hard carbon as described in claim 1, characterized in that, In step S5, the carbonization temperature is 800℃-1400℃ and the carbonization time is 10-24h.
9. A negative electrode active material, characterized in that, Prepared using the method described in any one of claims 1-8.
10. A battery, characterized in that, It includes the negative electrode active material as described in claim 9.