A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite

Abstract

The present invention discloses a low-temperature homogeneous regeneration method for waste lithium-ion battery graphite. The method comprises ball-milling and compacting a magnetic metal with waste graphite, followed by low-temperature calcination under an inert atmosphere to produce a pre-repaired graphite material. The pre-repaired graphite material is then ground again and dispersed in a solution, followed by magnetic separation to remove the magnetic metal, thereby producing a regenerated graphite material. This method utilizes the ability of the magnetic metal to induce low-temperature repair of defect sites in the graphite and near its surface when in close contact with the graphite. The resulting regenerated graphite material exhibits excellent electrochemical properties, and the magnetic metal can be removed by magnetic separation, further enhancing the purity of the regenerated graphite material.

Description

Technical Field

[0001] The invention relates to a low-temperature homogeneous regeneration method for waste lithium-ion battery graphite, belonging to the technical field of waste battery recycling. Background Art

[0002] Graphite, a strategic mineral resource in my country, plays a key role in the country's national economy. Currently, graphite has been successfully used as anode material for lithium-ion batteries. With the rapid development of the new energy industry, lithium-ion batteries have been widely used across various industries in my country. However, due to their limited lifespan, lithium-ion batteries are inevitably becoming obsolete. Facing the massive influx of used batteries, establishing high-quality recycling channels for used batteries is a critical step in achieving a closed-loop system for the new energy industry.

[0003] Currently, the recycling of graphite negative electrodes for lithium-ion batteries is divided into wet recycling and direct regeneration. Wet recycling involves extracting key metal elements from the negative electrodes using reagents such as acids and alkalis, and then stacking the resulting graphite waste. Currently, most of the waste from wet processing is used as fuel and incinerated, resulting in a significant waste of resources. Direct regeneration, on the other hand, requires long-term high-temperature calcination at 2800°C to repair the graphite crystal phase. While direct regeneration offers high graphite resource utilization efficiency, high energy consumption and significant pollution have resulted in a low economic value for graphite recycling. Most direct regeneration companies do not repair waste graphite. Furthermore, waste graphite materials from different sources suffer varying levels of damage, and simple repairs cannot induce uniform graphite repair. This results in uneven performance of the regenerated graphite, ultimately preventing the recycled graphite from entering the commercial market.

[0004] Chinese patent CN117954725A discloses a method for recovering the capacity of graphite anode materials from waste lithium-ion batteries by mixing them with an ammonium salt-strong base composite salt, followed by calcination, washing, and drying to obtain a precursor material. The precursor material is then mixed with a low-boiling-point organic metal salt-energy-storage anion powder composite and vacuum calcined to obtain high-value regenerated graphite. This method can effectively restore the capacity of graphite anode materials, but the initial strong base and high-temperature etching process changes the internal structure of the graphite material. Furthermore, the restoration of the charge-discharge capacity of the graphite electrode material relies on the introduction of metal ions to form bonds with sulfur or selenium atoms to form transition metal sulfur-selenium compounds, a high-capacity electrode material. This introduces some magnetic material that cannot be removed during the restoration process, which can adversely affect the commercial distribution of graphite anode materials for lithium batteries. Summary of the Invention

[0005] To address the problems of existing waste graphite regeneration, such as poor performance, high energy consumption, and uneven performance, the present invention aims to provide a low-temperature, homogeneous regeneration method for waste lithium-ion battery graphite. This method introduces a magnetic metal into the waste graphite and compacts it. This method utilizes the close contact between the magnetic metal and the graphite to induce low-temperature repair of defects in the graphite and near the surface. This allows for a short, low-energy regeneration process for waste graphite. The resulting regenerated graphite material exhibits excellent rate performance and high capacity.

[0006] In order to achieve the above technical objectives, the present invention provides a low-temperature homogeneous regeneration method for waste lithium-ion battery graphite. The method comprises the following steps: mixing magnetic metal with waste graphite by ball milling and compacting, and then calcining at low temperature under an inert atmosphere to obtain a preliminary repaired graphite material; the preliminary repaired graphite material is ground again and dispersed in a solution, and then the magnetic metal is removed by magnetic separation to obtain a regenerated graphite material.

[0007] In the technical solution of the present invention, compaction treatment is a prerequisite for repair, and the introduction of magnetic metal is the key to repair. Specifically, the present invention can induce low-temperature repair of graphite and near-surface defect sites by introducing magnetic metal. The principle is: first, the magnetic metal has a special electronic structure. When in close contact with graphite, the free electrons in the magnetic metal can migrate to the defect sites of graphite, fill the electron loss, stabilize the structure of graphite, and promote the repair of defects; second, the magnetic metal will generate a local electric field near the graphite surface. For defects caused by processes such as lithium ion deintercalation, the local electric field helps to adjust the arrangement of atoms and promote the gradual healing of defects; third, the magnetic metal can play an effective catalytic role on the graphite surface, which can reduce the activation energy of the reaction, thereby achieving repair at low temperatures. The catalytic effect of the magnetic metal on waste graphite depends on the contact degree between the waste graphite and the magnetic metal. If there is no contact, the catalytic effect formed by the interface is difficult to complete. In addition, some graphite that is not in contact cannot be repaired, resulting in incomplete repair effect. The present invention significantly improves the contact between waste graphite and magnetic materials through compaction, enhancing the surface and interface repair effectiveness of waste graphite, ultimately achieving low-temperature homogeneous repair of waste graphite. Furthermore, compared to existing technologies, the repaired graphite material can be removed through magnetic separation, further increasing the purity of the regenerated graphite material without affecting the capacity and performance of the repaired graphite material, enabling its commercial application.

[0008] The inventors have found that the present invention adopts magnetic metal compared to magnetic metal salt (magnetic metal ion), and particle size is larger, is conducive to the magnetic separation of rear end, avoids the generation of spent acid, waste liquid. If magnetic metal is replaced with corresponding metal salt, metal salt can produce inhomogeneous metal element particles due to decomposition and reduction during calcination, and the particles with smaller scales cannot be separated by magnetic separation and remain in the regenerated graphite material, can only pass through pickling, and can produce secondary damage to the regenerated graphite material by pickling. In addition, traditional metal salt catalysis process causes in the regeneration process, may introduce anions that are difficult to wash, and organometallic salts can introduce organic carbon chains that can decompose amorphous carbon, ultimately leading to a reduction in the yield of the material, and electrochemical side reactions aggravate. And the large-scale magnetic particles in the present invention, contribute to the migration of carbon particles on the graphite surface under low temperature environment, fill the defects of the failed graphite particle surface, provide pre-embedded interlayer spacing for lithium ion storage, improve the capacity and rate performance of the material.

[0009] As a preferred solution, the waste graphite comes from waste lithium-ion batteries, electrode materials, unfilled lithium-ion batteries, etc. purchased on the market.

[0010] As a preferred solution, the magnetic metal is at least one of cobalt, nickel and iron.

[0011] As a preferred solution, the mass ratio of the magnetic metal to the waste graphite is (0.1-10):1. The mass ratio of the magnetic metal to the waste graphite has a direct impact on the graphite repair effect. If the mass ratio is too low, the magnetic metal content is too low, which makes it difficult to provide sufficient active sites for the waste graphite and cannot induce uniform repair of the waste graphite near the surface at low temperatures. On the other hand, if the mass ratio is too high and the magnetic metal content is too high, not only will the processing cost increase and the thermal energy utilization be seriously insufficient, but it will also increase the difficulty of subsequent magnetic separation to remove the magnetic metal and even lead to a decrease in the purity of the recycled graphite material.

[0012] As a preferred solution, the magnetic metal is a powder with a D50 of 0.1 μm to 200 μm. If the D50 of the magnetic metal is too small, the particle size is small, the metal powder is highly active, and it is prone to spontaneous combustion in the air, which is not conducive to production and difficult to completely remove through subsequent magnetic separation. On the other hand, if the D50 of the magnetic metal is too large, the particle size is large, and it is difficult for the magnetic metal to form close and uniform contact with the waste graphite, making it difficult to achieve near-surface homogeneous repair of the waste graphite.

[0013] As a preferred solution, the compaction pressure is 10 to 100 MPa. If the pressure is too low during the compaction process, it is difficult for the scrap graphite to form close contact with the magnetic metal, reducing the homogeneous repair effect. However, if the pressure is too high, the scrap graphite particles will be damaged during the compaction process, damaging the overall graphite structure. At the same time, the severely compacted mixture is difficult to grind and disperse, making it difficult to remove the magnetic metal later.

[0014] As a preferred solution, the low-temperature calcination atmosphere is one of argon, hydrogen and a hydrogen-argon mixture.

[0015] As a preferred solution, the low-temperature calcination conditions are: a temperature of 500-1500°C for 1-20 hours. If the calcination temperature is too low or the calcination time is too short, the magnetic metal activity and the carbon atom mobility in the graphite are difficult to fully activate, making it difficult to repair defects. If the calcination temperature is too high, the magnetic metal will melt and aggregate, and the induced repair effect will not be achieved.

[0016] As a preferred solution, the solution contains at least one dispersant selected from CMC (carboxymethyl cellulose), ethanol and sodium dodecylphenyl cyclane, and the mass ratio between the dispersant and the preliminary repaired graphite material is 1g: (10-1)kg. The present invention forms a tight connection between the material and the graphite after compaction treatment. If it is only simply crushed, the agglomerates formed by some magnetic metals and graphite are difficult to dissociate, and some magnetic particles may remain in the repaired graphite, resulting in the magnetic material content of the repaired graphite being too high, which is difficult to meet commercial application standards. Therefore, the graphite is dispersed in an aqueous solution to increase the dissociation degree of the graphite material. In addition, the surface hydrophobicity of graphite is relatively strong. If it is directly placed in an aqueous solution, the graphite material is difficult to disperse in the aqueous solution. Therefore, the present invention adds an appropriate amount of dispersant to promote the dispersion and dissociation of graphite particles in the aqueous phase.

[0017] As a preferred solution, the magnetic separation uses a wet magnetic separator with a magnetic separation intensity of 0.5T to 2.0T and 3 to 6 cycles. Within this selected magnetic separation intensity range, the magnetic metal introduced into the initial repaired graphite material can be effectively removed. Multiple cycles can further completely remove the magnetic metal and ensure the quality of the regenerated graphite material.

[0018] As a preferred solution, the content of magnetic metal powder in the regenerated graphite material is less than 50 ppm.

[0019] The ball milling process involved in the present invention is a conventional operation process in the prior art, and its purpose is to convert the mixed material after compaction and sintering into powder to facilitate the next step of dispersion and magnetic separation.

[0020] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0021] 1) The waste graphite regeneration process provided by the present invention is simple, has a short process flow, low energy consumption, and the method is simple to operate, has a short cycle, and high economic benefits.

[0022] 2) The present invention introduces magnetic metal into waste graphite and performs compaction treatment. When the magnetic metal is in close contact with the graphite, it can induce low-temperature repair of defect sites in the graphite and near the surface. The obtained regenerated graphite material has good electrochemical properties, and the magnetic metal can be removed by magnetic separation, further improving the purity of the regenerated graphite material.

[0023] 3) The method of the present invention can achieve homogeneous regeneration of different types of waste graphite. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are electrochemical performance diagrams of three batches of graphite materials repaired by Example 5 of the present invention.

[0025] Figure 2 Graphs showing the electrochemical properties of three batches of graphite materials repaired by Example 1 of the present invention.

[0026] Depend on Figure 1 and Figure 2 By comparison, it can be seen that the repair treatment combining the magnetic metal and compaction treatment of the present invention has little difference between batches of regenerated graphite materials, and homogeneous regeneration can be achieved. DETAILED DESCRIPTION

[0027] The following examples are used to illustrate the present invention but are not intended to limit the scope of protection of the claims of the present invention.

[0028] The waste graphite used in the present invention comes from waste batteries purchased on the market. The waste lithium-ion batteries are subjected to processes such as safe discharge, manual disassembly, and negative pressure drying to obtain relatively pure waste lithium-ion battery negative electrode sheets, which are then subjected to multiple ultrasonic water washing and drying processes to obtain waste lithium-ion battery graphite materials.

[0029] Through the treatment process of magnetic metal, compaction treatment and magnetic separation in the embodiment of the present invention, the content of magnetic metal powder in the obtained regenerated graphite material is less than 50 ppm.

[0030] In the embodiment of the present invention, the volume ratio of the dispersant to water in the aqueous solution containing the dispersant is 1:1, and the mass ratio of the dispersant to the preliminary repaired graphite material is 0.001g:1g.

[0031] Example 1 (comparative example)

[0032] 1g of waste graphite powder is compacted in a press at a pressure of 20MPa. The compacted material is placed in a tubular furnace and calcined at 800℃ for 10 hours under a nitrogen atmosphere. The material is then cooled naturally to produce recycled graphite material.

[0033] Example 2 (Comparative Example)

[0034] Magnetic metal powder (D50, 10μm) and waste graphite were weighed in a mass ratio of 2:1 (2g of cobalt and 1g of graphite), then placed in a ball mill for ball milling. The mixed material was calcined at 800°C for 10 hours under a nitrogen atmosphere and then cooled naturally. The cooled material was placed in a ball mill again and ground, and the ground material was dispersed in an aqueous solution containing ethanol. Magnetic separation was performed using a wet magnetic separator with a magnetic separation intensity of 1.0T and 5 magnetic separations. The material after magnetic separation was dried to obtain recycled graphite material.

[0035] Example 3 (Comparative Example)

[0036] Magnetic metal powder (D50, 10 μm) and waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, followed by natural cooling. The cooled material is placed in a ball mill again and ground, and the ground material is magnetically separated using a dry magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separations. The material after magnetic separation is dried to obtain recycled graphite material.

[0037] Example 4 (Comparative Example)

[0038] Magnetic metal powder (D50, 10 μm) and waste graphite were weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite). The mixed powders were then milled in a ball mill. The mixed powders were compacted in a press at a pressure of 20 MPa. Magnetic separation was performed using a wet magnetic separator (using an ethanol-water solution as the dispersant) at a magnetic separation intensity of 1.0 T and five passes. The separated material was then dried to produce recycled graphite.

[0039] Example 5

[0040] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0041] Example 6

[0042] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (nickel is 2 g, graphite is 1 g), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again and ground, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0043] Example 7

[0044] The magnetic metal powder (D50, 0.1 μm) and waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0045] Example 8

[0046] The magnetic metal powder (D50, 200μm) and the waste graphite are weighed in a mass ratio of 2:1 (2g of cobalt and 1g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20MPa. The pressed material is placed in a tubular furnace and calcined at 800°C for 10h in a nitrogen atmosphere, followed by natural cooling. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0047] Example 9

[0048] Magnetic metal powder (D50, 10 μm) and waste graphite are weighed in a mass ratio of 0.1:1 (0.1 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, followed by natural cooling. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0049] Example 10

[0050] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 10:1 (10 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0051] Example 11

[0052] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 10 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0053] Example 12

[0054] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 100 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0055] Example 13

[0056] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under an argon atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0057] Example 14

[0058] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 500 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation frequency of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0059] Example 15

[0060] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 1500 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation number of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0061] Example 16

[0062] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 1 hour under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation frequency of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0063] Example 17

[0064] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 20 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation frequency of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0065] Example 18

[0066] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours in a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing CMC. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and 5 magnetic separation times. The material after magnetic separation is dried to obtain recycled graphite material.

[0067] Example 19

[0068] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 0.5 T and a magnetic separation frequency of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0069] Example 20

[0070] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 2.0 T and a magnetic separation frequency of 5 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0071] Example 21

[0072] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation frequency of 3 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0073] Example 22

[0074] The magnetic metal powder (D50, 10 μm) and the waste graphite are weighed in a mass ratio of 2:1 (2 g of cobalt and 1 g of graphite), and then placed in a ball mill for ball milling and mixing. The mixed powder is compacted under a press with a pressure of 20 MPa. The pressed material is placed in a tubular furnace and calcined at 800 ° C for 10 hours under a nitrogen atmosphere, and then cooled naturally. The cooled material is placed in a ball mill again for grinding, and the ground material is dispersed in an aqueous solution containing ethanol. Magnetic separation is performed using a wet magnetic separator with a magnetic separation intensity of 1.0 T and a magnetic separation frequency of 6 times. The material after magnetic separation is dried to obtain recycled graphite material.

[0075] The regenerated graphite materials of Examples 1 to 22 were tested according to the following method. The results are shown in Table 1.

[0076] 1) Sample preparation

[0077] In each embodiment, the waste graphite comes from waste batteries purchased on the market. The recycled material, acetylene black, and sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 8 / 1 / 1 and a certain amount of deionized water is added to prepare a uniform slurry. The obtained slurry is coated on a copper foil and then placed in a vacuum oven at 100°C for 24 hours for drying. The obtained electrode is cut by a slicer into small discs with a diameter of 1 cm to become the obtained positive electrode material, wherein the copper foil is loaded with more than 1 mg of active substance.

[0078] The obtained positive electrode sheet, electrolyte, lithium sheet, battery shell, separator, etc. are placed in an argon glove box for battery assembly. After sealing, the obtained battery is an assembled button cell.

[0079] Note: All examples adopt the above-mentioned electrode material preparation method.

[0080] 2) Test method

[0081] After the button cell was left to rest for 12 hours, it was placed on a blue-electric test channel for electrochemical performance testing, with the current density set to 1.0C and the voltage range set to 0.01-2.5V. The data obtained is directly displayed on the blue-electric tester and can be used directly.

[0082] Table 1 Electrochemical performance test results of each embodiment

[0083]

[0084]

[0085]

Claims

1. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite, characterized in that: The magnetic metal is mixed with waste graphite by ball milling and compacting, and then placed in an inert atmosphere for low-temperature calcination to obtain a preliminary repaired graphite material; the preliminary repaired graphite material is ground again and dispersed in a solution, and then the magnetic metal is removed by magnetic separation to obtain a regenerated graphite material; The magnetic metal is at least one of cobalt, nickel, and iron; The mass ratio of the magnetic metal to the waste graphite is (0.1-10):1; The low-temperature calcination conditions are: temperature of 500-1500° C., and time of 1-20 hours.

2. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite according to claim 1, characterized in that: The magnetic metal is powder with a D50 of 0.1 μm to 200 μm.

3. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite according to claim 2, characterized in that: The compaction pressure is 10-100 MPa.

4. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite according to claim 1, characterized in that: The solution contains at least one dispersant selected from CMC, ethanol and sodium dodecylphenyl cyclate, and the mass ratio of the dispersant to the preliminary repaired graphite material is 1g:(10~1)kg.

5. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite according to claim 4, characterized in that: The magnetic separation adopts a wet magnetic separator with a magnetic separation intensity of 0.5T~2.0T and is circulated 3~6 times.

6. A low-temperature homogeneous regeneration method for waste lithium-ion battery graphite according to claim 1, characterized in that: The content of magnetic metal powder in the regenerated graphite material is less than 50 ppm.

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