Battery negative electrode material prepared based on waste C / C composite material, preparation method of battery negative electrode material, pole piece and secondary battery

Abstract

The invention discloses a battery negative electrode material prepared based on a waste C / C composite material, a preparation method of the battery negative electrode material, a pole piece and a secondary battery, and belongs to the technical field of lithium ion battery materials. According to the method, cutting materials and leftover materials are used as raw materials, the 100% recycling rate of waste resources is achieved, the preparation process is short and easy to control, the method is suitable for large-scale production, and cost is reduced; the obtained battery negative electrode material does not need to separate carbon powder and carbon fibers and has excellent comprehensive performance; the synergistic effect of the carbon powder and the carbon fiber enables the negative electrode material to have excellent performance in multiple aspects, and the negative electrode material has higher specific capacity and first charge-discharge efficiency, so that the energy density and the power density of the battery are improved; and meanwhile, the cycle life of the battery is prolonged due to good mechanical property and thermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a battery negative electrode material prepared based on waste C / C composite materials, a preparation method thereof, a pole piece and a secondary battery. Background Art

[0002] With the rapid development of new energy vehicles and portable electronic devices, the demand for high-performance lithium-ion batteries continues to increase. The negative electrode material of lithium-ion batteries is one of the key factors affecting battery performance. The negative electrode material currently used in commercial applications is mainly graphite, but its theoretical specific capacity is low and it is difficult to meet the growing demand for high energy density. Therefore, the development of new high-performance negative electrode materials has become a research hotspot. C / C composites are usually composed of carbon fiber reinforcement and carbon matrix, and have the advantages of high strength, high modulus, and high temperature resistance. However, in recent years, with the tremendous development of my country's aerospace and photovoltaic industries, the consumption of C / C composites has increased year by year. A new problem that arises is that C / C composites will generate a large amount of waste during production and processing, including cuttings and scraps. How to recycle these wastes and produce high value-added products has become a key issue that cannot be avoided. Waste C / C composites have unique structural characteristics and rich carbon sources, and are a potential precursor for lithium battery negative electrode materials. Therefore, how to effectively recycle waste C / C composites and realize their application in battery negative electrode materials is of great economic and environmental significance.

[0003] In the prior art, patent CN107732216A discloses a method for preparing lithium-ion negative electrode materials using C / C composite material particles. The method includes the steps of material selection, coating, calcination, graphitization, etc., wherein the conditions for the C / C composite material in the material selection are relatively cumbersome, and the experimental conditions cannot make full use of the C / C composite material. Patent CN 117105684A discloses a method for preparing high-density and high-strength carbon materials based on waste carbon-carbon composite materials. The preparation process involves multiple steps, including high-energy ball milling, resin coating, mixing of mesophase carbon microspheres, cold molding and carbonization treatment. The process is complex, the cost is high, the production cycle is long, and the equipment and process control requirements are high. There are mainly the following problems in the recycling of waste C / C composite materials: single recycling method and low resource utilization rate: currently, simple methods such as mechanical crushing and incineration are mainly used to treat waste C / C composite materials, which makes it difficult to achieve effective separation and high-value utilization of carbon fiber and matrix carbon; lack of targeted recycling technology: due to the structural characteristics of waste C / C composite materials, there is a lack of efficient and environmentally friendly recycling technology, making it difficult to achieve directional recycling of carbon fiber and matrix carbon; low added value of recycled products: the performance of carbon fiber and matrix carbon obtained by existing recycling technology has declined significantly, and it is difficult to directly use them in high value-added fields, such as lithium battery negative electrode materials. Summary of the invention

[0004] Aiming at the technical problems that the utilization rate of existing waste C / C composite materials is low, the process for preparing battery negative electrode materials based on the waste C / C composite materials is complex, the cost is high, the theoretical specific capacity is low, the structural stability is poor, the cycle stability is poor, and the like, the present invention provides a battery negative electrode material prepared based on the waste C / C composite materials, and a preparation method thereof, a pole piece and a secondary battery. The waste C / C composite materials are used as raw materials, and the process is improved through density screening treatment, multiple ball milling and the like. There is no need to separate carbon powder and carbon fiber, and the battery negative electrode material is directly prepared from the mixed state of the waste C / C composite materials. The process is simple and the cost is low, and the specific capacity and the first coulomb efficiency of the battery are effectively improved, thereby realizing efficient recovery and high-value utilization, and providing a high-performance and low-cost negative electrode material for lithium-ion batteries.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing a battery negative electrode material based on waste C / C composite materials, comprising: S1, density 0.8-2.0 g / cm 3 The waste C / C composite material is cleaned, cut and crushed to obtain coarse particles of the waste C / C composite material; S2, soaking and cleaning the coarse particles of the waste C / C composite material with a mixed solution, and ball milling to obtain carbon and carbon fiber mixed particles with refined particle size, wherein the mixed solution is ethanol, pure water or a mixed solution of the two; S3, washing, drying and sieving the carbon and carbon fiber mixed particles with refined particle size to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0006] Furthermore, in S1, the density is selected to be 1.2 g / cm 3 -1.6g / cm 3 of waste C / C composite materials.

[0007] Furthermore, in S1, the cutting is to cut the waste C / C composite material into pieces with a volume of less than 1 cm 3 Small pieces.

[0008] In S2, the volume ratio of pure water to ethanol in the mixed solution is in the range of (1-9): (9-1).

[0009] Furthermore, the volume ratio of pure water to ethanol in the mixed solution is in the range of (3-6): (7-4).

[0010] In S2, the ball milling is dry ball milling or wet ball milling; The solvent used in wet ball milling is any one of ultrapure water, ethanol, isopropanol or a mixed solvent of any two combinations, and the mass volume ratio of the material to the solvent is 1: (2-10).

[0011] The mass ratio of ball-milling zirconium oxide balls to materials is 1-10:1, the rotation speed is 400 r / min-1000 r / min, the ball-milling time is 1-12 h, and the ball-milling times are 1-5 times.

[0012] Furthermore, the mass ratio of the ball-milled zirconia balls to the material is (5-10): 1.

[0013] The ball milling is preferably wet ball milling, the ball milling speed is preferably 700-900 r / min, the ball milling time is preferably 3-10 h, the number of ball millings is preferably 2-4 times, and the mass volume ratio of the material to the solvent is preferably 1: (2-6).

[0014] Furthermore, the ball milling in the embodiment is wet ball milling, the solvent used is ethanol, the mass volume ratio of the material to the solvent is 1:5, the ball milling is performed twice, the mass ratio of the zirconia balls to the material in the first ball milling is 5:1, the rotation speed is 800 r / min, and the ball milling time is 4h, and the mass ratio of the zirconia balls to the material in the second ball milling is 3:1, the rotation speed is 800 r / min, and the ball milling time is 5h.

[0015] The particle size of the refined carbon and carbon fiber mixed material particles ranges from 100 nm to 5 μm.

[0016] The drying conditions are: drying at 60°C-150°C for 1h-48h.

[0017] Furthermore, the drying temperature is preferably 80-120° C., and the drying time is preferably 12-30 h.

[0018] The battery negative electrode material obtained by the above method.

[0019] The above-mentioned battery negative electrode material is used in the preparation of battery negative electrode plates and secondary batteries.

[0020] The present invention also provides a negative electrode plate, which is made of a negative electrode material using waste C / C composite material as raw material.

[0021] In the present invention, the negative electrode sheet can be prepared by a common preparation method in the art, generally comprising the following steps: the mixture of the negative electrode material using the waste C / C composite material as raw material, the binder and the conductive agent is homogenized and then coated to obtain the negative electrode sheet. The binder is any one or a combination of polyacrylic acid, polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber, and the conductive agent is any one or a combination of carbon black, graphite, acetylene black, and conductive carbon fiber.

[0022] The present invention also provides a secondary battery, which comprises the above-mentioned negative electrode plate.

[0023] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing anode materials for batteries based on waste C / C composite materials. The method does not require separation of carbon powder and carbon fiber, and directly uses the mixed state of waste C / C composite materials for preparation, thereby simplifying the process flow and reducing production costs. At the same time, the obtained cathode materials exhibit excellent performance in many aspects. The density is selected to be 0.8-2.0 g / cm 3 The waste C / C composite material is used as a raw material, which helps to adjust the ratio of carbon powder and carbon fiber, maintain the structural stability of the C / C composite material, and ensure that the conductivity of the material will not be significantly reduced due to structural damage during the subsequent processing, thereby ensuring the long-term stability of the negative electrode material in the battery, and helping to improve the uniformity of the material during the subsequent processing, so as to prepare a battery negative electrode material with more stable performance. The particle size can be optimized and the particle dispersibility can be improved through multiple ball milling treatments, which can increase the specific surface area of ​​the material, provide more active sites, and thus improve the storage capacity and reaction kinetics of lithium ions; at the same time, the refined particles are easier to be evenly dispersed in the electrode slurry, reduce agglomeration, and are conducive to forming a stable electrode structure. Using the cuttings and scraps in the production and processing of waste C / C composite materials as raw materials, 100% efficient recycling of waste resources is achieved. The present invention has a simple process, low cost, is suitable for large-scale production, and can flexibly control material properties by adjusting parameters such as ball milling time and rotation speed.

[0025] The battery negative electrode material obtained by the preparation method of the present invention has high conductivity due to the presence of carbon fibers, which can reduce the electron transmission resistance inside the electrode and thus improve the first coulomb efficiency of the battery; the presence of carbon fibers enhances the mechanical properties of the electrode, so that it can maintain structural stability during the charge and discharge process and extend the service life of the battery; the presence of carbon fibers gives it excellent thermal stability and can maintain good mechanical strength and chemical stability in a high temperature environment, so it is suitable for electrode materials in a high temperature environment and improves the high temperature resistance of the battery.

[0026] The application provided by the present invention is that the battery negative electrode material is made of waste C / C composite material, retains the mixed state of carbon fiber and carbon powder, and has a higher specific capacity, thereby improving the energy density of the battery; the high conductivity makes the electron transmission inside the battery smoother, and improves the first coulomb efficiency of the battery; the good mechanical properties and thermal stability extend the cycle life of the battery and reduce the performance degradation of the battery during the charging and discharging process; the negative electrode material is applied to lithium-ion batteries, which can improve the energy density, power density and cycle life of the battery, and meet the needs of electric vehicles, portable electronic devices and other fields for high-performance batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the operation flow chart of the present invention; Figure 2 This is a SEM photo of the C / C composite waste before mechanical crushing in Example 1 of the present invention; Figure 3 : is the charge and discharge curve in Example 1 of the present invention; Figure 4 This is the charge and discharge curve in Example 5 of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially. 1. Specific embodiments Example 1 This embodiment provides a method for preparing a negative electrode material for a battery based on waste C / C composite materials, which specifically includes: S1, density 1.2g / cm 3 -1.6 g / cm 3 The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse particles of waste C / C composite materials.

[0031] S2, weigh 4 portions of 2g of coarse particles of waste C / C composite materials, put them into ball mills respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 5:1, the rotation speed is 800r / min, ball milling is performed for 4h, and drying is performed after ball milling to obtain coarse particles of waste C / C composite materials after the first ball milling; weigh the coarse particles of waste C / C composite materials after the first ball milling, put them into the ball mill with zirconia balls at a mass ratio of 1:3, and ball mill for the second time for 5h at the same rotation speed to obtain carbon and carbon fiber mixed particles with refined particle size.

[0032] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0033] The SEM image of the C / C composite waste before mechanical crushing in step 1 of this embodiment is as follows: Figure 2 As shown, from Figure 2 It can be seen that the surface of the material is relatively rough, with carbon fibers and pyrolytic carbon interlaced, tightly combined, and with clear texture.

[0034] Assembly and testing of button half-cells: The battery negative electrode material prepared based on waste C / C composite materials in this embodiment, conductive carbon black (Super P) as a conductive agent, and polyacrylic acid (PAA) as a binder are weighed according to mass percentages of 80%, 10%, and 10%, respectively, and a slurry is prepared using a beater. Subsequently, the slurry is coated, dried, and cut into pieces, and assembled into button half-cells in a glove box. Finally, the LANDIAN equipment is used for testing, and the discharge cut-off voltage is set to 0.005V and the charge cut-off voltage is set to 1.5V. The battery is discharged to 0.005V with constant currents of 0.1C, 0.05C, and 0.02C, respectively, and the discharge specific capacity is recorded; then the battery is charged to 1.5V with a constant current of 0.1C, and the charge specific capacity is recorded; the above charge and discharge process is repeated for two cycles to evaluate the performance of the battery. The charge and discharge curves of the secondary battery assembled using the battery negative electrode material prepared based on waste C / C composite materials in Example 1 are shown in the figure. Figure 3 shown.

[0035] By the attached Figure 3 From the data of the charge and discharge curve of this embodiment, it can be seen that the first discharge specific capacity of the button battery prepared in Example 1 is 408.71 mAh / g, the first charge specific capacity is 352.05 mAh / g, and the calculated first coulombic efficiency is 86.14%, indicating that the battery negative electrode material prepared in Example 1 of the present invention has good charge and discharge performance and coulombic efficiency, and has potential application value.

[0036] Example 2 This embodiment provides a method for preparing a negative electrode material for a battery based on waste C / C composite materials on the basis of embodiment 1, which specifically includes: S1 is the same as S1 in Example 1.

[0037] S2, weigh 4 portions of 2g of coarse particles of waste C / C composite materials, put them into ball mills respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 5:1, the rotation speed is 1000r / min, ball milling is performed for 4h, and drying is performed after ball milling to obtain coarse particles of waste C / C composite materials after the first ball milling; weigh the coarse particles of waste C / C composite materials after the first ball milling, put them into the ball mill with zirconia balls at a mass ratio of 1:3, and ball mill for the second time for 5h at the same rotation speed to obtain carbon and carbon fiber mixed particles with refined particle size.

[0038] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0039] Example 3 This embodiment provides a method for preparing a negative electrode material for a battery based on waste C / C composite materials on the basis of embodiment 1, which specifically includes: S1 is the same as S1 in Example 1.

[0040] S2, weigh 4 portions of 2g of coarse particles of waste C / C composite materials and put them into a ball mill respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 5:1, the rotation speed is 800r / min, ball milling is performed for 4h, and drying is performed after ball milling to obtain coarse particles of waste C / C composite materials after the first ball milling; weigh the coarse particles of waste C / C composite materials after the first ball milling, put them into a ball mill with zirconia balls at a mass ratio of 1:2, and ball mill for the second time for 6h at the same rotation speed to obtain carbon and carbon fiber mixed particles with refined particle size.

[0041] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0042] Example 4 This embodiment provides a method for preparing a negative electrode material for a battery based on waste C / C composite materials on the basis of embodiment 1, which specifically includes: S1, density 0.8g / cm 3 -1.2 g / cm 3The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse particles of waste C / C composite materials.

[0043] S2 is the same as S2 in Example 1.

[0044] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0045] Example 5 This embodiment provides a method for preparing a negative electrode material for a battery based on waste C / C composite materials on the basis of embodiment 1, which specifically includes: S1, density 1.6g / cm 3 -2.0g / cm 3 The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse particles of waste C / C composite materials.

[0046] S2 is the same as S2 in Example 1.

[0047] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0048] The charge and discharge curves of the secondary battery assembled using the battery negative electrode material prepared based on the waste C / C composite material in Example 5 are as follows: Figure 4 shown.

[0049] From the attached picture Figure 4 From the data of the charge and discharge curve of this embodiment, it can be seen that the first discharge specific capacity of the button battery prepared in Example 5 is 448.76 mAh / g, the first charge specific capacity is 360.46 mAh / g, and the calculated first coulombic efficiency is 80.32%, indicating that the battery negative electrode material prepared in Example 5 of the present invention has good charge and discharge performance and coulombic efficiency, and has potential application value.

[0050] Comparative Example 1 S1, density 1.2g / cm 3 -1.6 g / cm 3 The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse carbon powder and carbon fiber mixed particles, and the coarse carbon and carbon fibers are separated.

[0051] S2, weigh 4 portions of 2g of coarse particles of waste C / C composite materials, put them into ball mills respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 5:1, the rotation speed is 800r / min, ball milling is performed for 4h, and drying is performed after ball milling to obtain coarse particles of waste C / C composite materials after the first ball milling; weigh the coarse particles of waste C / C composite materials after the first ball milling, put them into a ball mill with zirconia balls at a mass ratio of 1:3, and ball mill at the same rotation speed for 5h to obtain carbon particles with refined particle size.

[0052] S3, washing the refined carbon particles with anhydrous ethanol for 2-3 times, drying them in an oven at 100° C. for 24 hours, and obtaining a battery negative electrode material prepared based on the waste C / C composite material.

[0053] Comparative Example 2 S1, density 1.2g / cm 3 -1.6 g / cm 3 The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse particles of waste C / C composite materials.

[0054] S2, weigh 4 portions of 2 g of coarse particles of waste C / C composite materials, put them into ball mills respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 5:1, the rotation speed is 800 r / min, and the ball milling is performed for 4 hours to obtain carbon and carbon fiber mixed particles with refined particle size.

[0055] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0056] Comparative Example 3 S1, density 1.2g / cm 3 -1.6 g / cm 3 The waste C / C composite material is cut into pieces with a volume less than 1cm 3 The above materials are then crushed by a crusher to obtain coarse particles of waste C / C composite materials.

[0057] S2, weigh 4 portions of 2 g of coarse particles of waste C / C composite materials, put them into ball mills respectively, and add 10 mL of anhydrous ethanol to each portion, wherein the mass ratio of zirconia balls to coarse particles of waste C / C composite materials is 3:1, the speed is 800 r / min, and the ball milling is performed for 4 hours to obtain carbon and carbon fiber mixed particles with refined particle size.

[0058] S3, washing the refined carbon and carbon fiber mixed particles with anhydrous ethanol for 2-3 times, placing them in an oven at 100° C. and drying them for 24 hours to obtain a battery negative electrode material prepared based on the waste C / C composite material.

[0059] 2. Performance Test The battery negative electrode materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were used as negative electrode active materials to assemble button batteries.

[0060] According to the assembly and testing method of button batteries in Example 1, the battery negative electrode materials obtained in Examples 2 to 5 of the present invention and Comparative Examples 1 to 3 were assembled into button half-cells and performance tested. The specific test results are shown in Table 1.

[0061] Table 1: Battery performance data

[0062] It can be seen from the data in Table 1 that the first cycle charging capacity of Examples 1 to 5 ranges from 272.76 mAh / g to 360.46 mAh / g, indicating that the battery negative electrode material obtained by the method of the present invention can absorb relatively high electricity during the charging process, showing good charging performance, among which the charging capacity of Example 5 is the highest, reaching 360.46 mAh / g, and the charging efficiency or capacity advantage is more obvious; the first cycle discharge capacity of Examples 1 to 5 ranges from 327.41 mAh / g to 448.76 mAh / g, indicating that the battery negative electrode material obtained by the method of the present invention can release high electricity during the discharge process, showing good discharge performance. The discharge capacity of the battery negative electrode material in Example 5 is also the highest, which is 448.76 mAh / g, further demonstrating its superiority in discharge; the first coulombic efficiency of Examples 1 to 5 ranges from 80.32% to 86.14%. Coulombic efficiency is an important indicator for measuring the power loss during the charging and discharging process of the battery. A higher coulombic efficiency means that the battery loses less power during the charging and discharging process; the first coulombic efficiency of Examples 1 to 5 is slightly higher than that of Examples 2 to 3, but the overall difference is not large, indicating that the stability of the preparation process is good and a higher first coulombic efficiency can be maintained.

[0063] Compared with Comparative Example 1, the first cycle charge specific capacity and discharge specific capacity of the battery negative electrode material prepared in Example 1 of the present invention are significantly improved (352.05 mAh / g vs 163.9 mAh / g, 408.71 mAh / g vs 219.4 mAh / g), indicating that the presence of carbon fiber can improve the conductivity of the material, reduce the electron transport resistance inside the electrode, and thus improve the specific capacity of the battery; compared with Comparative Example 2, the first coulomb efficiency (86.14% vs 79.25%) and the first cycle charge and discharge specific capacity (352.05 mAh / g vs 250.90 mAh / g, 408.71 mAh / g vs 316.58mAh / g) were significantly improved, indicating that secondary ball milling can further refine the particles, increase the specific surface area, and promote lithium ion transmission, thereby effectively improving the specific capacity and the first coulombic efficiency; the battery negative electrode material prepared in Example 1 of the present invention also shows significant performance advantages compared with Comparative Example 3, indicating that the ball milling material ratio also has an important influence on the particle refinement of the material, and the appropriate material ratio can optimize the particle structure and improve the battery performance. In short, the battery negative electrode materials of Examples 1 to 5 perform well in charging performance, discharging performance and first coulombic efficiency; the comparison with Comparative Examples 1 to 3 further proves the importance of adding carbon fiber, secondary ball milling treatment and ball milling material ratio to improve battery performance.

[0064] From the above data, it can be seen that the battery negative electrode material prepared by the present invention has a high specific capacity and first coulombic efficiency, showing good electrochemical performance; by using waste C / C composite materials, effective utilization of resources is achieved and production costs are reduced; waste C / C composite materials of different density ranges can prepare negative electrode materials with stable performance, indicating that the process has good stability; the mixed state of carbon powder and carbon fiber is crucial to maintaining the electrochemical performance of the negative electrode material, and the performance decreases significantly after separation; the preparation process is simple, easy to control, and suitable for large-scale production. The method for preparing battery negative electrode materials based on waste C / C composite materials provided by the present invention has significant technical effects, and provides a new way for the recycling of waste resources and the preparation of high-performance battery negative electrode materials.

[0065] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a negative electrode material for a battery based on waste C / C composite materials, characterized in that: include: S1, density 0.8-2.0 g / cm 3 The waste C / C composite material is washed and then mechanically crushed to obtain coarse particles of the waste C / C composite material; S2, soaking and cleaning the coarse particles of the waste C / C composite material with a mixed solution, and ball milling to obtain carbon and carbon fiber mixed particles with refined particle size, wherein the mixed solution is ethanol, pure water or a mixed solution of the two; S3, washing, drying and sieving the carbon and carbon fiber mixed particles with refined particle size to obtain a battery negative electrode material prepared based on the waste C / C composite material.

2. The method for preparing a negative electrode material for a battery based on waste C / C composite material according to claim 1, characterized in that: In S2, the volume ratio of pure water to ethanol in the mixed solution is (1-9): (9-1).

3. The method for preparing a negative electrode material for a battery based on waste C / C composite material according to claim 1, characterized in that: In S2, the ball milling is dry ball milling or wet ball milling; The solvent used in wet ball milling is any one of ultrapure water, ethanol, isopropanol or a mixed solvent of any two combinations, and the mass volume ratio of the material to the solvent is 1: (2-10); The mass ratio of ball-milled zirconium oxide balls to materials is (1-10): 1; The ball milling speed is 400-1000 r / min, the ball milling time is 1-12 h, and the ball milling times are 1-5 times.

4. The method for preparing a negative electrode material for a battery based on waste C / C composite material according to claim 1, characterized in that: In S2, the particle size of the refined carbon and carbon fiber mixture particles ranges from 100 nm to 5 μm.

5. The method for preparing a negative electrode material for a battery based on waste C / C composite material according to claim 1, characterized in that: In S3, the drying conditions are: drying temperature is 60°C-150°C, and drying time is 1 h-48 h.

6. A battery negative electrode material obtained by the method according to any one of claims 1 to 5.

7. Use of the battery negative electrode material according to claim 6 in the preparation of battery negative electrode sheets and secondary batteries.

8. A battery negative electrode plate, characterized in that: The battery negative electrode sheet is obtained by coating the battery negative electrode material according to claim 6 with a binder and a conductive agent after homogenization.

9. The negative electrode plate of the battery according to claim 8, characterized in that: The binder is any one or a combination of polyacrylic acid, polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber; the conductive agent is any one or a combination of carbon black, graphite, acetylene black, and conductive carbon fiber.

10. A secondary battery, characterized in that: The negative electrode sheet of the secondary battery is obtained from the negative electrode sheet of the battery according to any one of claims 8 or 9.

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