Recycling method of lithium battery graphite negative electrode material

Abstract

The invention relates to the technical field of battery negative electrode materials, in particular to a method for recycling a graphite negative electrode of a lithium ion battery by using organisms. According to the method, acid leaching is carried out on metal elements in the recovered graphite by utilizing an acid environment generated in the growth and metabolism process of strains, so that impurities in the retired graphite can be thoroughly removed; after full reaction, bacteria can form a biomass coating layer on the surface of the graphite, after high-temperature carbonization treatment, the capacity of the graphite can be increased to more than 352 mAh / g, and the electrochemical performance of the graphite is equivalent to that of a conventional graphite product in the market. Aiming at regeneration and repair of the graphite negative electrode material of the scrapped lithium ion battery, the process route is simple, and the performance of the repaired graphite is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of battery anode materials, and particularly relates to a method for recycling and reusing the graphite anode of a lithium-ion battery by using organisms. Background Art

[0002] In order to reduce the dependence on fossil fuels and reduce environmental pollution, electric vehicles have developed rapidly. Lithium-ion batteries (LIBs) have become ideal power carriers for digital electronics, electric vehicles, and energy storage power stations due to their advantages such as high energy density, long cycle life, and no memory effect. Lithium-ion batteries are widely used in multiple fields such as electronics, transportation, and energy storage tools. However, since their average lifespan is only 3 - 8 years, it indicates an upcoming large wave of retired lithium-ion batteries. Although cascade utilization can temporarily extend the battery life, its fundamental goal is only to delay the final retirement, and lithium-ion batteries with a final capacity retention rate of less than 60% inevitably face disposal problems.

[0003] Currently, there are already related technologies for recycling and reusing lithium-ion batteries. For example, CN117865145A treats the negative electrode sheet with DMC solution to remove the binder, obtains graphite recycling material, then pickles the graphite with hydrochloric acid, nitric acid, etc. to remove metal elements such as Cu and Li in the graphite, then dissolves polymethyl methacrylate in NMP to coat the graphite, and finally obtains recycled graphite through high-temperature treatment. Although this method can effectively remove metal ions in the graphite and ultra-high temperature can also repair the graphite, it causes great environmental pollution and high energy consumption; another example is CN118993062A, which uses multi-stage pyrolysis to treat the binder, uses the oxidation method to further remove organic matter, and then obtains recycled graphite through pickling with hydrochloric acid, etc. and high-temperature treatment. This method can also effectively treat the metal elements of the graphite, but it also has the disadvantages of large pollution and high energy consumption.

[0004] Therefore, there is an urgent need for a green, efficient, and pollution-free method to recycle and process the anode materials of a large number of waste lithium-ion batteries (SLIBs). Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for recycling and reusing the graphite anode of a lithium-ion battery by using organisms to solve the above technical problems.

[0006] To achieve the above purpose, a method for recycling and reusing a graphite anode material of a lithium battery provided by the present invention includes the steps: S1: Obtain graphite precursor A obtained by recycling waste lithium-ion batteries; S2: Place the strain in a petri dish for cultivation. After reaching the expected concentration, concentrated strain B is obtained. The strain includes one or more of sulfur bacteria such as Thiobacillus thiooxidans, Ferrobacillus ferrooxidans, Acidithiobacillus ferrooxidans, and Thiothrix, and one or more of Nitrosomonas, Nitrosospira, Nitrosococcus, Nitrosolobus, Nitrospina, and Nitrococcus. S3: Mix the graphite precursor A and the concentrated strain B, stir and cultivate until the expected pH is reached. Then cultivate at 20 - 30 °C for 2 - 5 days, and then perform sieving separation. After washing the solid matter, dry the retained matter on the sieve to obtain the bio - coated precursor graphite C. The expected pH is between 0 and 6.5. S4: Perform high - temperature carbonization treatment on the bio - coated precursor graphite C to obtain recycled graphite.

[0007] Furthermore, in step S1, the recycled waste lithium - ion battery is subjected to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, the waste graphite powder is ultrasonically cleaned and dried in an oven to a constant weight. After drying, the black powder is ground and sieved to obtain graphite precursor A.

[0008] Furthermore, the Dv50 range of the graphite precursor A obtained after sieving is 1.5 - 40 μm.

[0009] Furthermore, the Dv50 range of the graphite precursor A obtained after sieving is 6 - 20 μm.

[0010] Furthermore, the Dv50 range of the graphite precursor A obtained after sieving is 8 - 15 μm.

[0011] Furthermore, the expected pH is between 0 and 6.5.

[0012] Furthermore, the expected pH is between 0.5 and 2.

[0013] Furthermore, the expected pH is 1 and the cultivation temperature is 25 °C.

[0014] Furthermore, the solution after sieving separation in step S4 is used for continuous cultivation as concentrated colony B.

[0015] Furthermore, the temperature range of the high - temperature carbonization treatment in step S4 is 600 - 1400 °C.

[0016] Furthermore, the cultivation time in step S3 is 3 days.

[0017] Furthermore, after cultivating for 2 - 5 days in step S3, perform sieving separation. Wash the solid matter with distilled water and dry the retained matter on the sieve at 90 - 120 °C to a constant weight to obtain the bio - coated precursor graphite C.

[0018] By utilizing the acidic environment generated during the biological growth and metabolism process, the metal elements in the recycled graphite are subjected to acid leaching, which can remove the impurities in the retired graphite more thoroughly and is of great help for the reconstruction in terms of structure. Moreover, after the reaction is complete, bacteria will form a biomass coating layer on the surface of the graphite. After high-temperature carbonization treatment, the graphite capacity can be increased to more than 352 mAh / g, and the electrochemical performance is comparable to that of conventional graphite products on the market. The present invention will regenerate and repair the graphite negative electrode material of waste lithium-ion batteries with a simple route and excellent performance after graphite repair. Brief Description of the Drawings

[0019] The drawings, as part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings: Figure 1 It is a schematic process flow diagram of the method for recycling and reusing the graphite negative electrode of a lithium-ion battery by using organisms in the present invention.

[0020] Figure 2 It is an electron microscope image of graphite before repair.

[0021] Figure 3 It is an electron microscope image of the graphite after high-temperature repair with a biomass coating obtained by the method for recycling and reusing the graphite negative electrode of a lithium-ion battery by using organisms in Example 1 of the present invention.

[0022] The realization, functional features, and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Detailed Embodiments

[0023] The following clearly and completely describes the technical problems to be solved, the technical solutions adopted, and the technical effects achieved by the embodiments of the present invention in conjunction with the drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other equivalent or significantly modified embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The embodiments of the present invention can be embodied in various different ways as defined and covered in the claims.

[0024] It should be noted that in the following description, many specific details are given for the convenience of understanding. However, it is obvious that the present invention can be implemented without these specific details.

[0025] It should be noted that, without clear limitations or conflicts, the various embodiments and their technical features in the present invention can be combined with each other to form technical solutions.

[0026] Example 1: S1: The recycled waste lithium-ion batteries are subjected to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, the waste graphite powder is ultrasonically cleaned, thoroughly mixed, and dried to constant weight in an oven at 105 °C. The dried black powder is passed through a 200-mesh standard sieve to obtain recycled graphite precursor A.

[0027] S2: Thiobacillus thiooxidans (a commonly commercially available variety) uses NH4 + as the nitrogen source and CO2 (from air) as the carbon source, and obtains the energy required for growth and metabolism by oxidizing sulfur monosalt for cultivation. The strain concentration is measured. When the concentration exceeds 10^8 cells / mL, concentrated strain B is obtained; S3: The graphite precursor A and the concentrated strain B are mixed and cultured. Stirring is carried out at 25 rmp. When the pH reaches 1, it is cultured at 25 °C for 3 days. The solution is separated by sieving, the material on the sieve is repeatedly washed with distilled water, and dried to constant weight in an oven at 105 °C to obtain bio-coated precursor graphite C. The sieved solution, after high-speed centrifugation, the lower sediment can be used as the strain to continue the cultivation of concentrated strain B; S4: The bio-coated precursor graphite C is treated at 1150 °C and recycled graphite D is obtained after sieving.

[0028] Example 2: S1: The recycled waste lithium-ion batteries are subjected to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, the waste graphite powder is ultrasonically cleaned, thoroughly mixed, and dried to constant weight in an oven at 105 °C. The dried black powder is passed through a 200-mesh standard sieve to obtain recycled graphite precursor A.

[0029] S2: Filamentous sulfur bacteria (a commonly commercially available variety) uses NH4 + as the nitrogen source and CO2 (from air) as the carbon source, and obtains the energy required for growth and metabolism by oxidizing sulfur monosalt for cultivation. The strain concentration is measured. When the concentration exceeds 10^8 cells / mL, concentrated strain B is obtained; S3: The graphite precursor A and the concentrated strain B are mixed and cultured. Stirring is carried out at 25 rmp. When the pH reaches 1, it is cultured at 25 °C for 3 days. The solution is separated by sieving, the material on the sieve is repeatedly washed with distilled water, and dried to constant weight in an oven at 105 °C to obtain bio-coated precursor graphite C. The sieved solution, after high-speed centrifugation, the lower sediment can be used as the strain to continue the cultivation of concentrated strain B S4: Treat the bio-coated precursor graphite C at 1150 °C, and obtain the recycled graphite D after sieving.

[0030] Example 3: S1: Subject the recycled waste lithium-ion batteries to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, ultrasonically clean the waste graphite powder, thoroughly mix it, and dry it to a constant weight in an oven at 105 °C. Pass the dried black powder through a 200-mesh standard sieve to obtain the recycled graphite precursor A.

[0031] S2: Use Nitrosococcus (a commonly commercially available variety) with NH4 + as the nitrogen source and CO2 (from air) as the carbon source. Through the oxidation of NH4 + to obtain the energy required for growth and metabolism for cultivation. Measure the strain concentration. When the concentration exceeds 10^8 cells / mL, the concentrated strain B is obtained. S3: Mix and cultivate the graphite precursor A and the concentrated strain B. Stir at 25 rmp. When the pH reaches 1, cultivate at 25 °C for 3 days. Separate the solution by sieving, repeatedly wash the residue on the sieve with distilled water, and dry it to a constant weight in an oven at 105 °C to obtain the bio-coated precursor graphite C. For the sieved solution, after high-speed centrifugation, the sediment in the lower layer can be used as the strain for the cultivation of the concentrated strain B. S4: Treat the bio-coated precursor graphite C at 1150 °C, and obtain the recycled graphite D after sieving.

[0032] Example 4: S1: Subject the recycled waste lithium-ion batteries to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, ultrasonically clean the waste graphite powder, thoroughly mix it, and dry it to a constant weight in an oven at 105 °C. Pass the dried black powder through a 200-mesh standard sieve to obtain the recycled graphite precursor A.

[0033] S2: Use Nitrospina (a commonly commercially available variety) with NH4 + as the nitrogen source and CO2 (from air) as the carbon source. Through the oxidation of NH4 + to obtain the energy required for growth and metabolism for cultivation. Measure the strain concentration. When the concentration exceeds 10^8 cells / mL, the concentrated strain B is obtained. S3: Mix and cultivate the graphite precursor A and the concentrated strain B. Stir at 25 rmp. When the pH reaches 1, cultivate at 25 °C for 3 days. Separate the solution by sieving, repeatedly wash the residue on the sieve with distilled water, and dry it to a constant weight in an oven at 105 °C to obtain the bio-coated precursor graphite C. For the sieved solution, after high-speed centrifugation, the sediment in the lower layer can be used as the strain for the cultivation of the concentrated strain B. S4: Treat the bio-coated precursor graphite C at 1150 °C, and obtain the recycled graphite D after sieving.

[0034] Comparative Example 1: The difference between this comparative example and Example 1 lies in that the stirring rate in Step S3 is 10 rmp, and the remaining steps and parameters are the same as those in Example 1.

[0035] Comparative Example 2: The difference between this comparative example and Example 1 lies in that the stirring rate in Step S3 is 40 rmp, and the remaining steps and parameters are the same as those in Example 1.

[0036] Comparative Example 3: The difference between this comparative example and Example 1 lies in that the cultivation time in Step S3 is 1 day, and the remaining steps and parameters are the same as those in Example 1.

[0037] Comparative Example 4: The difference between this comparative example and Example 1 lies in that the cultivation time in Step S3 is 5 days, and the remaining steps and parameters are the same as those in Example 1.

[0038] Comparative Example 5: The difference between this comparative example and Example 1 lies in that the cultivation temperature in Step S3 is 15 °C, and the remaining steps and parameters are the same as those in Example 1.

[0039] Comparative Example 6: The difference between this comparative example and Example 1 lies in that the cultivation temperature in Step S3 is 35 °C, and the remaining steps and parameters are the same as those in Example 1.

[0040] Comparative Example 7: Graphite precursor A that only goes through Step S1 of Example 1.

[0041] Respectively use the graphite anode materials in Examples 1-4 and Comparative Examples 1-7 as the anode active materials, mix them evenly with a conductive agent, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) according to a mass ratio of 95:1:2.5:1.5, then coat them on a copper foil, and then place the electrode sheet in a vacuum drying treatment at 105 °C for 24 h; assemble a coin cell in a glove box. Among them, the electrolyte in the electrolyte is LiPF6, the concentration is 1 M, the solvent is composed of dimethyl carbonate, ethylene carbonate, and ethyl methyl carbonate with a volume ratio of 1:1:1, the counter electrode is a lithium sheet, and the first Coulombic efficiency and cycle performance are tested. The test conditions are as follows, and the results are shown in Table 1.

[0042] First Coulombic efficiency test: First discharge at a current of 0.1C until 1 mV, let it stand for 10 min, and then charge at a rate of 0.1C to 2.00 V to test the first Coulombic efficiency of the graphite.

[0043] Cyclic performance test: After the first charge and discharge test of the material, it is discharged at a constant current and constant voltage (0.5C) to 0.1 V, charged at a constant current (0.5 C) to 2.0 V, and cycled 1500 times, and the capacity retention rate at the 800th cycle is calculated.

[0044] Table 1 Battery performance data of each sample Combined with Figure 1 、 2 and 3 and Table 1, it can be seen from the performance data in Table 1 that the overall performance of the graphite anode material prepared by the present invention is better than that of the graphite anode materials prepared in Comparative Examples 1-7. The specific analysis is as follows.

[0045] Comparing Example 1 with Comparative Examples 1-2, it can be seen that the stirring rate has an impact on the recycling of waste graphite. Too low a stirring rate will result in insufficient leaching of metal ions, and too high a stirring rate may cause the bacteria to come into contact with the graphite too frequently, resulting in the fragmentation of the bacteria, thereby reducing the leaching efficiency, increasing the ash content in the graphite, and deteriorating its electrochemical performance.

[0046] Comparing Example 1 with Comparative Examples 3-4, it can be seen that the cultivation has an impact on the recycling of waste graphite. A shorter cultivation time will result in insufficient leaching of metal ions, increasing the ash content in the graphite and deteriorating its electrochemical performance. Too long a time will result in too thick a biological coating on the surface, increasing the residual carbon after high-temperature treatment, reducing the initial efficiency, and thus causing a certain deterioration in the cycle.

[0047] Comparing Example 1 with Comparative Examples 5-6, it can be seen that too high or too low a temperature will cause a decrease in the metabolism of the bacteria, thereby reducing the leaching rate of metal ions and deteriorating the performance of the recycled graphite.

[0048] Comparing Examples 1-2 with Examples 3-4, it can be seen that there is little difference between sulfur bacteria and nitrifying bacteria in the recycling of graphite, and both can effectively treat graphite.

[0049] Comparing Examples 1-4, Comparative Examples 1-6 and Comparative Example 7, it can be seen that the electrochemistry of the graphite treated with bacteria is better than that of the untreated graphite precursor, indicating that the bacteria have a significant effect on the recycling treatment of graphite.

[0050] In the present invention, sulfur bacteria and nitrifying bacteria are utilized to generate an acidic environment during their growth and metabolism processes, thereby acid-leaching waste graphite to remove the enriched metal ions therein. Meanwhile, the extracellular polymeric substances secreted by the strains and the aggregated strains form a biological coating layer on the solid surface, covering the graphite surface, filling the cracks caused by cycling and making it smoother. Subsequently, the graphite coated with the biological coating layer is subjected to high-temperature treatment to repair its crystal structure, and at the same time, the biological coating layer is decomposed into amorphous carbon to form a carbon core-shell structure for the graphite, thereby realizing its repair and regeneration, and further improving its electrochemical performance and enhancing the cycling performance of the recycled graphite.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for recycling and reusing a graphite anode material for a lithium battery, characterized in that, Including the steps: S1: Obtain graphite precursor A recovered from recycled waste lithium-ion batteries. S2: Place the strain in a petri dish for cultivation. After reaching the expected concentration, obtain concentrated strain B. The strains include one or more of sulfur-oxidizing bacteria such as Thiobacillus thiooxidans, Ferrobacillus ferrooxidans, Thiobacillus ferrooxidans, and Thiothrix, and one or more of Nitrosomonas, Nitrosospira, Nitrosococcus, Nitrosolobus, Nitrospina, and Nitrococcus. S3: Mix the graphite precursor A and the concentrated strain B, stir and cultivate until the expected pH is reached. Then cultivate at 20-30 °C for 2-5 days, and then perform sieving separation. Wash the solid matter and dry the retained material on the sieve to obtain biologically coated precursor graphite C. The expected pH is between 0 and 6.

5. S4: Perform high-temperature carbonization treatment on the biologically coated precursor graphite C to obtain recycled graphite D.

2. The recycling method of the graphite anode material for lithium batteries according to claim 1, characterized in that, In step S1, the recycled waste lithium-ion batteries are subjected to discharge disassembly, component classification, and mechanical coarse crushing to obtain waste graphite powder. Then, the waste graphite powder is ultrasonically cleaned and dried in an oven to a constant weight. After drying, the black powder is ground and sieved to obtain graphite precursor A.

3. The recycling method of the graphite anode material for lithium batteries according to claim 2, characterized in that The Dv50 range of the graphite precursor A obtained after sieving is 1.5-40 μm.

4. The recycling method of the graphite anode material for lithium batteries according to claim 3, characterized in that The Dv50 range of the graphite precursor A obtained after sieving is 6-20 μm.

5. The recycling method of the graphite anode material of the lithium battery according to claim 1, characterized in that, The expected pH is between 0.5 and 2.

6. The recycling method of the graphite anode material of the lithium battery according to claim 1, characterized in that, The expected pH is 1, and the cultivation temperature is 25 °C.

7. The recycling method of the graphite anode material for lithium batteries according to claim 1, characterized in that, The solution after sieving separation in step S4 is used for continuous cultivation to serve as concentrated colony B.

8. The recycling method of the graphite anode material of the lithium battery according to claim 1, characterized in that, The temperature range of the high-temperature carbonization treatment in step S4 is 600-1400 °C.

9. The recycling method of the graphite anode material of the lithium battery according to claim 1, characterized in that, The cultivation time in step S3 is 3 days.

10. The recycling method of the graphite anode material for lithium batteries according to claim 1, characterized in that, After cultivating for 2-5 days in step S3, perform sieving separation. Wash the solid matter with distilled water and dry the retained material on the sieve at 90-120 °C to a constant weight to obtain biologically coated precursor graphite C.

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