Waste artificial graphite regeneration method, regenerated material and application thereof

Abstract

The invention belongs to the field of waste artificial graphite regeneration, and particularly relates to a waste artificial graphite regeneration method, a regenerated material and application thereof, the regeneration method comprises the following steps: carrying out normal pressure liquid phase modification on waste artificial graphite in an organic acid solution in advance, and then putting the modified waste artificial graphite in an inorganic acid solution for positive pressure liquid phase modification to prepare a modified material; mixing the modified material with a Mn source, a metal N source, a first carbon source and a binder to obtain a mixture, then performing heat treatment on the mixture in a hydrogen-containing atmosphere, and then performing negative-pressure annealing treatment to obtain a heat-treated material; the metal N source comprises a compound of at least one of iron, cobalt and nickel; and mixing the heat-treated material with lithium salt and a second carbon source, and carrying out roasting treatment to obtain the graphite regenerated material. The regeneration method disclosed by the invention is particularly suitable for repairing the artificial graphite waste which is difficult to treat, so that the artificial graphite waste can be repaired to obtain a material with excellent capacity, long circulation and particularly low-temperature stability.

Description

Technical Field

[0001] The present invention belongs to the field of recycling of waste lithium-ion battery anode materials, and particularly relates to the field of artificial graphite regeneration of waste batteries. Background Art

[0002] As a commercial lithium-ion battery anode material with relatively stable performance, graphite has extremely broad application prospects. With the increasing consumption of lithium-ion batteries, the quantity of scrapped lithium-ion batteries has also shown a blowout state. As an important resource supporting the development of the national economy, graphite is of great significance for recycling.

[0003] The graphite anode materials of lithium-ion batteries mainly include natural graphite and artificial graphite. However, the structures of natural graphite and artificial graphite are different, and different problems need to be faced in regeneration. For example, for artificial graphite, different from natural graphite, the material is in large lamellar form, and there are more serious problems of structural collapse and interlayer damage. In addition, there is also a deeper problem that it is difficult to remove the embedded impurities, and the regeneration is more difficult.

[0004] However, the prior art pays less attention to the physical and chemical differences between natural graphite and artificial graphite, and usually they are regenerated and repaired together, so it is difficult to homogenize the performance of the regenerated materials. For example, the Chinese patent document with the publication number CN116093474A discloses a green regeneration and reuse method for waste artificial graphite anodes of lithium-ion batteries, which specifically records a recovery method of performing a mixed intercalation treatment of CO 2 and N 2 on the waste artificial graphite anode. Another example is that the Chinese patent document with the publication number CN110265743A discloses a regeneration method for an ionic liquid-coated waste power battery artificial graphite material, which specifically records a process of removing impurities from the recovered artificial graphite material and then performing carbon coating by ball milling and annealing with an ionic liquid to achieve material regeneration.

[0005] In addition, the Chinese patent document with the publication number CN119108691A discloses a preparation method for a high-performance energy storage type anode artificial graphite material, which specifically records a scheme of calcining the graphite material peeled from waste lithium-ion batteries with a chloride salt and then modifying it in a hydrogen peroxide solution.

[0006] In summary, there are few existing regeneration processes for waste artificial graphite. However, the existing processes are still difficult to adapt to the problems such as high structural collapse, high damage, and deep embedding of impurities in artificial graphite, which make it difficult to deeply repair, and it is difficult to regenerate graphite materials that take into account both high capacity and low-temperature stability. Summary of the Invention

[0007] Aiming at the problems faced by the regeneration of waste artificial graphite, the first object of the present invention is to provide a method for regenerating waste artificial graphite, aiming to solve the problems such as high collapse, defects and deep embedding of impurities in waste artificial graphite, which are difficult to remove, and then regenerate materials with high capacity, long cycle life and low-temperature performance.

[0008] The second object of the present invention is to provide a regenerated material obtained by the regeneration method and its application.

[0009] The third object of the present invention is to provide a lithium-ion battery containing the regenerated material, its negative electrode and negative electrode material.

[0010] Different from waste natural graphite materials, waste artificial graphite materials have a larger lamellar structure, and there are problems such as greater structural collapse, interlayer damage and deep embedding of interlayer impurities during the cycling process. In view of the physical and chemical characteristics of waste artificial graphite, the existing conventional methods cannot achieve the effects of deep impurity removal and deep structural repair. In view of this problem, the present invention provides the following improvement solutions:

[0011] A method for regenerating waste artificial graphite, which comprises pre-treating waste artificial graphite by atmospheric pressure liquid-phase modification in an organic acid solution, and then placing it in an inorganic acid solution for positive pressure liquid-phase modification to obtain a modified material;

[0012] Mix the modified material with a Mn source, a metal N source, a first carbon source and a binder to obtain a mixed material, and then heat-treat it under a hydrogen-containing atmosphere, and then perform negative pressure annealing treatment to obtain a heat-treated material; the metal N source includes compounds of at least one metal among iron, cobalt and nickel;

[0013] Mix the heat-treated material with a lithium salt and a second carbon source and perform a roasting treatment to obtain a graphite regenerated material.

[0014] In view of the more significant problems such as structural collapse and structural defects in waste artificial graphite, the present invention provides a regeneration idea specifically adapted to waste artificial graphite. It innovatively pre-treats waste artificial graphite by atmospheric pressure liquid-phase treatment with an organic acid, and then performs positive pressure liquid-phase treatment on the graphite modified by atmospheric pressure with an inorganic acid, and then cooperates with heat treatment under a hydrogen-containing atmosphere, negative pressure annealing and subsequent lithium salt-assisted roasting and infiltration treatment of the Mn source and the metal N source. In this way, synergy can be unexpectedly achieved, which can adapt to the treatment problems of waste artificial graphite, effectively optimize its interlayer and surface structures, and in addition, can also optimize the surface characteristics, and a material with excellent capacity, long cycle life, especially long cycle stability at low temperature can be regenerated based on waste artificial graphite.

[0015] In the present invention, the waste artificial graphite is a material obtained by peeling the negative electrode of a retired battery with artificial graphite as the negative electrode.

[0016] Preferably, in the waste artificial graphite, the content of artificial graphite is 80 wt.% or more.

[0017] In the present invention, the waste artificial graphite is pre-treated by atmospheric pressure modification with an organic acid, and then combined with subsequent positive pressure modification with an inorganic acid. In this way, it can adapt to the physical and chemical characteristics of the waste artificial graphite, effectively improve the interlayer, optimize the interlayer structure, facilitate combination with subsequent processes, strengthen the modification effect of the waste artificial graphite, and further improve the capacity and low-temperature performance of the regenerated graphite material.

[0018] The organic acid in the organic acid solution includes at least one of formic acid, acetic acid, phenylpropionic acid, and phenylalanine.

[0019] Preferably, the concentration of the organic acid in the organic acid solution is 0.01 - 0.2 M, and further can be 0.01 - 0.05 M.

[0020] Preferably, the liquid-solid ratio in the atmospheric pressure liquid phase modification stage is 1 - 10 ml / g.

[0021] Preferably, the temperature in the atmospheric pressure liquid phase modification stage is 20 - 90 °C, and further can be 50 - 75 °C.

[0022] Preferably, the time of atmospheric pressure liquid phase modification is 2 - 8 h, and further can be 3 - 4 h.

[0023] In the present invention, the graphite material modified by atmospheric pressure with an organic acid is placed in a solution of an inorganic acid for the above-mentioned positive pressure liquid phase treatment.

[0024] In the present invention, the inorganic acid solution is at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0025] Preferably, the concentration of the inorganic acid in the inorganic acid solution is 0.02 - 0.5 M, and further can be 0.2 - 0.4 M.

[0026] Preferably, the positive pressure liquid phase modification treatment stage is carried out in a closed container.

[0027] Preferably, the temperature of the positive pressure liquid phase modification is 140 - 200 °C.

[0028] Preferably, the liquid-solid ratio of the positive pressure liquid phase modification is 1 - 10 ml / g.

[0029] Preferably, the time of the positive pressure liquid phase modification is 2 - 8 h, and further can be 2 - 4 h.

[0030] In the present invention, a manganese source, a metal N source, and a modifier are pre-compounded, and further combined with subsequent heat treatment in a hydrogen-containing atmosphere and negative-pressure annealing treatment. In this way, the surface of graphite can be repaired in advance. In addition, metal and moderately alloyed active sites can be embedded, so that it can be combined with subsequent lithium salt-assisted roasting to in-situ construct special metal lithium salt sites based on the penetration of lithium salt, thereby improving the performance of the prepared material such as capacity and low-temperature stability.

[0031] In the present invention, the manganese source is at least one of manganese nitrate, manganese acetylacetonate, manganese acetate, manganese citrate, manganese tungstate, manganese trifluoromethanesulfonate, manganese gluconate, manganese molybdate, and manganese hypophosphite; preferably at least one of manganese tungstate and manganese molybdate. Research shows that under the preferred manganese source, it can be combined with other processes to obtain better adaptability and synergy, and better material capacity, long cycle life, and low-temperature performance can be obtained.

[0032] Preferably, the metal N source is at least one of nitrates, chlorides, and oxalates of metal N.

[0033] Preferably, the carbon source is one or several of glucose, sucrose, organic polymers, starch, etc.

[0034] Preferably, the binder is at least one of sodium alginate, polyacrylic acid, polyvinylidene fluoride, carboxymethyl cellulose, and gum arabic.

[0035] Preferably, the mass ratio of the modifier, manganese source, metal N source, carbon source, and binder is 100:0.001 - 0.2:0.005 - 0.2:3 - 8:0.5 - 2; further, it can be 100:0.05 - 0.1:0.01 - 0.05:5 - 6:1 - 2.

[0036] In the present invention, the hydrogen-containing atmosphere is a mixture of hydrogen and a protective gas.

[0037] Preferably, the hydrogen content in the hydrogen-containing atmosphere is 2 - 10 v%, and further it can be 3 - 6 v%.

[0038] Preferably, the temperature in the heat treatment and annealing treatment stages is 500 - 850 °C, and further it can be 750 - 800 °C.

[0039] Preferably, the time for the heat treatment and annealing treatment is 1 - 6 h respectively.

[0040] Preferably, the negative pressure can be a conventional vacuum pressure, for example, it can be below 200 Pa.

[0041] In the present invention, the heat-treated material, lithium salt, and second carbon source are compounded and subjected to roasting treatment, so that it is beneficial for the internal infiltration of lithium during the roasting process and the physical and chemical reactions of the embedded metals and moderate alloy materials in the heat-treated material, thereby improving the long cycle and low-temperature performance of the regenerated material.

[0042] In the present invention, the lithium salt includes at least one of lithium chloride, lithium formate, lithium benzoate, lithium oxalate, lithium phosphate, lithium isopropoxide, lithium methoxide, n-butyllithium, lithium hexafluorophosphate, lithium aluminum hydride, and lithium niobate, and preferably lithium niobate. Research shows that under the preferred lithium salt, in combination with other processes, better compatibility and synergy can be obtained, and better material capacity, long cycle, and low-temperature performance can be achieved.

[0043] Preferably, the second carbon source can be at least one of coal tar pitch, petroleum asphalt, polyvinyl alcohol, polyacrylonitrile, etc.

[0044] Preferably, the mass ratio of the heat-treated material, lithium salt, second carbon source to the lithium source is 100:3 - 8:0.05 - 0.2.

[0045] Preferably, the roasting temperature is 900 - 1250 °C, and further can be 950 - 1050 °C.

[0046] Preferably, the roasting time is 2 - 8 h, and further is 4 - 5 h.

[0047] Preferably, the roasting stage is carried out under positive pressure. Preferably, the positive pressure is 1.5 - 2.5 atm. The atm is the standard atmospheric pressure. Research shows that under the preferred positive-pressure roasting, in combination with other processes, better compatibility and synergy can be obtained, and better material capacity, long cycle, and low-temperature performance can be achieved.

[0048] The present invention also provides a regenerated graphite material prepared by the method for regenerating waste artificial graphite described above.

[0049] The preparation method of the present invention can endow the prepared material with special physical and chemical characteristics, and the material prepared by the preparation method can realize the efficient utilization of difficult-to-regenerate artificial graphite and resourcefully obtain a regenerated material with excellent capacity and low-temperature performance.

[0050] The present invention also provides an application of the regenerated graphite material prepared by the method for regenerating waste artificial graphite described above, which is used as a negative electrode active material for preparing lithium-ion batteries.

[0051] The present invention also provides a lithium-ion battery, which includes the regenerated graphite material prepared by the method for regenerating waste artificial graphite described above.

[0052] For the lithium-ion battery of the present invention, except for including the recycled graphite material of the present invention, other components and structural relationships can be well-known.

[0053] Beneficial effects

[0054] The method of the present invention can adapt to the physical and chemical characteristics of waste artificial graphite, can achieve its deep repair, and can regenerate a material with high capacity and excellent long-cycle and low-temperature long-cycle stability.

[0055] Research also shows that by jointly controlling the type of organic acid, the type of lithium salt, and the air pressure in the lithium salt calcination stage, it is expected to further synergistically optimize the physical and chemical properties of the prepared material, which helps to further improve the long-cycle, especially the low-temperature long-cycle effect of the artificial graphite repair material. Description of the drawings

[0056] Appendix Figure 1 SEM of the waste artificial graphite raw material in Example 1;

[0057] Appendix Figure 2 SEM of the product regenerated in Example 1. Specific embodiments

[0058] The following illustrates the specific steps of the present invention through examples. It should be understood that these examples are only for illustrating the present invention and do not limit the scope of the present invention in any way. The various processes and methods not described in detail in the present invention are conventional methods well-known in the art.

[0059] A method for recycling and regenerating waste artificial graphite of the present invention, its steps are, for example:

[0060] 1. Crush the waste artificial graphite to obtain particles with a median particle size of 5-8 μm;

[0061] 2. Organic acid treatment: Place the above powder in an organic acid for atmospheric pressure modification treatment. After the reaction ends, perform solid-liquid separation, filter cake washing and drying.

[0062] The organic acid mentioned refers to one or several of formic acid, acetic acid, phenylpropionic acid, phenylalanine; the concentration of the acid is 0.01-0.2 M; the liquid-solid ratio (volume ratio) is 1-10 ml / g; the reaction time is 2-8 h, and the reaction temperature is 20-90 °C.

[0063] 3. Inorganic acid treatment: Place the obtained powder in an inorganic acid, seal it in a container, and perform liquid-phase modification treatment at a temperature above 120 °C. After the reaction ends, perform solid-liquid separation, filter cake washing and drying.

[0064] The inorganic acid mentioned above refers to one or more of hydrochloric acid, sulfuric acid, and nitric acid; the acid concentration is 0.02 - 0.5 M; the reaction time is 2 - 8 h, the reaction temperature is 140 - 200 °C, and preferably it is a mixed system of hydrochloric acid and hydrogen peroxide; the liquid-solid ratio (volume ratio) is 1 - 10 ml / g.

[0065] 4. Surface modification: After uniformly mixing the obtained powder with a manganese source, a metal source, a carbon source, a binder, and a solvent, spray drying is carried out to obtain a powder.

[0066] The manganese source mentioned above refers to one or more of manganese nitrate, manganese acetylacetonate, manganese acetate, manganese citrate, manganese tungstate, manganese trifluoromethanesulfonate, manganese gluconate, manganese molybdate, and manganese hypophosphite; the metal source refers to one or more of nitrates, chlorides, and oxalates of iron, cobalt, and nickel; the carbon source refers to one or more of glucose, sucrose, organic polymers, starch, etc.; the binder refers to one or more of sodium alginate, polyacrylic acid, polyvinylidene fluoride, carboxymethyl cellulose, gum arabic, etc.; the solvent is one or more of water, methanol, ethanol, etc. The mass ratio of graphite powder to the manganese source, the metal source, the carbon source, and the binder is 100:0.001 - 0.2:0.005 - 0.2:3 - 8:0.5 - 2.

[0067] 5. Perform a one-stage heat treatment on the obtained powder.

[0068] Place the obtained powder in an atmosphere furnace. First, under the atmosphere of 2 - 10% hydrogen + inert protective gas, heat up to 500 - 850 °C, keep it warm for 1 - 6 h, then evacuate to a vacuum degree of 20 - 200 Pa, perform vacuum annealing and keep it warm for 1 - 6 h, and then cool it with the furnace. Place the heat-treated powder in an acidic solution. The acidic solution mentioned above refers to one or more of hydrochloric acid, sulfuric acid, and nitric acid; the reaction time is 0.5 - 1 h. Perform solid-liquid separation and wash the filter cake with water.

[0069] 6. After uniformly mixing the obtained powder with a lithium source and a carbon source, perform a roasting treatment.

[0070] The lithium source mentioned above refers to one or more of lithium chloride, lithium formate, lithium benzoate, lithium oxalate, lithium phosphate, lithium isopropoxide, lithium methoxide, n-butyllithium, lithium hexafluorophosphate, lithium aluminum hydride, lithium niobate, etc., and preferably lithium aluminum hydride and lithium niobate; the carbon source refers to pitch; the mass ratio of the powder to the lithium source is 100:0.05 - 0.2; the mass ratio of the powder to the carbon source is 100:3 - 8; the heat treatment temperature is 900 - 1250 °C, and the treatment time is 2 - 8 h.

[0071] The waste artificial graphite described in the present invention is the waste obtained by disassembling the negative electrode of a waste battery with artificial graphite as the active material, and among them, the graphite content is between 88 - 91 wt.%.

[0072] Example 1

[0073] (1) Crush the waste artificial graphite to obtain particles with a median particle size of 6.3 μm;

[0074] (2) Place the above powder in an organic acid (acetic acid) with a concentration of 0.02 ± 0.005 M and stir for 3 - 4 h. The reaction temperature is 60 - 70 °C. After the reaction, perform solid-liquid separation, filter cake washing, and drying.

[0075] (3) Place the obtained powder in a mixed system of 0.2 ± 0.05 M hydrochloric acid and 0.1 ± 0.05 M nitric acid, seal it in a closed container, and then keep it at 150 ± 10 °C for 2 - 2.5 h. After the reaction, perform solid-liquid separation, filter cake washing, and drying.

[0076] (4) Dissolve and disperse the obtained powder, manganese molybdate, nickel oxalate, glucose, and polyacrylic acid in water according to a mass ratio of 100:0.1:0.01:5:1.5, and perform spray drying to obtain a powder.

[0077] (5) Place the obtained powder in an atmosphere furnace. First, under an atmosphere of 6% hydrogen + inert protective gas (Ar), heat it to 800 °C and keep it for 1 h. Then evacuate and continue to keep it under vacuum for 3 h (vacuum annealing). Subsequently, cool it with the furnace and place the powder in 0.2 M hydrochloric acid, stir for 0.5 h, and then perform solid-liquid separation and filter cake washing with water.

[0078] (6) Mix the obtained powder, lithium salt (lithium benzoate), and asphalt evenly according to a mass ratio of 100:0.1:5, and then perform atmospheric roasting treatment at 1000 °C under a nitrogen atmosphere for 4 h.

[0079] Example 2

[0080] Compared with Example 1, the difference is only that the conditions in step 2 are changed, and the organic acid is phenylalanine with a concentration of 0.015 M: other operations and parameters are the same as those in Example 1.

[0081] Example 3

[0082] Compared with Example 1, the difference is only that the conditions in step 3 are changed, and the experimental groups are:

[0083] Group A: The manganese source is manganese tungstate;

[0084] Group B: Dissolve and disperse the obtained powder, manganese molybdate, cobalt oxalate, sucrose, and carboxymethyl cellulose in water according to a mass ratio of 100:0.05:0.05:6:1.

[0085] Other operations and parameters are the same as those in Example 1.

[0086] Example 4

[0087] Compared with Example 1, the only difference is that in Step 5, the hydrogen content is 5 v%, the temperature is controlled at 750 °C, and after heat preservation for 1.5 h, heat preservation annealing is carried out under vacuum for 2.5 h. Other operations and parameters are the same as those in Example 1.

[0088] Example 5

[0089] Compared with Example 1, the only difference is that in Step 6, during the roasting stage, the system is pressurized with nitrogen, and the roasting system pressure is controlled at 2 - 2.5 atm. Other operations and parameters are the same as those in Example 1.

[0090] Example 6

[0091] Compared with Example 5, the only difference is that in Step 6, the lithium salt used is an equal amount of lithium niobate. Other operations and parameters are the same as those in Example 5.

[0092] Example 7

[0093] Compared with Example 1, the only difference is that in Step 6, after mixing the powder obtained in Step 5, the lithium salt, and asphalt evenly at a mass ratio of 100:0.05:6, atmospheric pressure roasting treatment is carried out in a nitrogen atmosphere at 950 °C, and the heat preservation time is 5 h. Other operations and parameters are the same as those in Example 1.

[0094] Comparative Example 1

[0095] Compared with Example 1, the only difference is that in Step 2, hydrochloric acid with an equal molar concentration is used to replace the acetic acid. Other operations and parameters are the same as those in Example 1.

[0096] Comparative Example 2

[0097] Compared with Example 1, the only difference is that in Step 3, the treatment process is carried out in an open container, and the temperature during the treatment stage is 90 °C. Other operations and parameters are the same as those in Example 1.

[0098] Comparative Example 3

[0099] Compared with Example 1, the only difference is that in Step 4, manganese molybdate is not added, and its missing weight is supplemented with an equal weight of nickel oxalate. Other operations and parameters are the same as those in Example 1.

[0100] Comparative Example 4

[0101] Compared with Example 1, the only difference is that in Step 4, nickel oxalate is not added, and its missing weight is supplemented with an equal weight of manganese molybdate. Other operations and parameters are the same as those in Example 1.

[0102] Comparative Example 5

[0103] Compared with Example 1, the only difference is that in step 5, the sintering atmosphere is Ar, and other operations and parameters are the same as those in Example 1.

[0104] Comparative Example 6

[0105] Compared with Example 1, the only difference is that in step 5, the annealing stage is carried out in an Ar atmosphere and the pressure is normal pressure, and other operations and parameters are the same as those in Example 1.

[0106] Comparative Example 7

[0107] Compared with Example 1, the only difference is that in step 6, no lithium salt is added, and other operations and parameters are the same as those in Example 1.

[0108] Comparative Example 8

[0109] Compared with Example 1, the only difference is that step 6 is not carried out, but the lithium salt and asphalt in step 6 are mixed with other components during step 4, and the treatment in step 5 is carried out to obtain the regenerated material, and other operations and parameters are the same as those in Example 1.

[0110] Using the regenerated graphite as the working electrode (dispersing the finally regenerated graphite, Super P, and LA133 in Example and Comparative Example in deionized water in a mass ratio of 95:2.5:2.5 to make a slurry, coating it on a copper foil, and drying it to be the working electrode), metallic lithium as the negative electrode, 1 mol / L LiPF6 in EC / EMC / DEC (volume ratio 1:1:1) as the electrolyte, and a PE-PP composite membrane as the separator to assemble a CR2032 coin cell in a dry glove box filled with argon, and performing electrochemical performance testing within a voltage range of 0.001 - 2.0 V at a certain temperature. The test results are shown in Table 1:

[0111] Table 1

[0112]

[0113] It can be seen from the examples and comparative examples that the waste artificial graphite is pre-treated by atmospheric pressure modification with organic acids and then combined with the subsequent positive pressure modification with inorganic acids. In this way, it can adapt to the physical and chemical characteristics of the waste artificial graphite, effectively improve the interlayer, optimize the interlayer structure, facilitate the combination with subsequent processes, strengthen the modification effect of the waste artificial graphite, and further improve the capacity of the regenerated graphite material and its long-cycle performance, especially the low-temperature long-cycle performance.

[0114] In addition, it can be seen from Example 1 and Example 2 that using phenylalanine as the organic acid to modify the waste artificial graphite can further combine and cooperate with the process, which helps to further improve the capacity and low-temperature long-cycle performance of the regenerated graphite material.

[0115] As can be seen from Examples 1 and 5, performing the roasting treatment under positive pressure can be further combined and coordinated with the process, which helps to further improve the capacity and low-temperature long-cycle performance of the regenerated graphite material.

Claims

1. A method for regenerating waste artificial graphite, characterized in that: The waste artificial graphite is preliminarily subjected to normal pressure liquid phase modification in an organic acid solution, and then placed in an inorganic acid solution for positive pressure liquid phase modification to obtain a modified material; The modified material is mixed with a Mn source, a metal N source, a first carbon source, and a binder to obtain a mixed material, which is then placed in a hydrogen-containing atmosphere for heat treatment, and then subjected to negative pressure annealing treatment to obtain a heat-treated material; the metal N source includes a compound of at least one metal selected from iron, cobalt, and nickel; The heat-treated material is mixed with a lithium salt and a second carbon source and calcined to obtain a graphite regeneration material.

2. The method for regenerating waste artificial graphite according to claim 1, wherein: Waste artificial graphite is a material obtained by stripping the negative electrode of retired batteries using artificial graphite as the negative electrode; Preferably, the content of artificial graphite in the waste artificial graphite is above 80wt.%.

3. The method for regenerating waste artificial graphite according to claim 1, characterized in that: The organic acid in the organic acid solution includes at least one of formic acid, acetic acid, phenylpropionic acid and phenylalanine; Preferably, the concentration of the organic acid in the organic acid solution is 0.01 to 0.2 M; Preferably, the liquid-to-solid ratio in the atmospheric pressure liquid phase modification treatment stage is 1 to 10 ml / g; Preferably, the temperature of the atmospheric pressure liquid phase modification stage is 20 to 90°C; Preferably, the time for normal pressure liquid phase modification is 2 to 8 hours.

4. The method for regenerating waste artificial graphite according to claim 1, wherein: The inorganic acid solution is at least one of hydrochloric acid, sulfuric acid and nitric acid; Preferably, the concentration of the inorganic acid in the inorganic acid solution is 0.02 to 0.5 M; Preferably, the positive pressure liquid phase modification treatment stage is carried out in a closed container; Preferably, the temperature of the positive pressure liquid phase modification is 140 to 200°C; Preferably, the liquid-to-solid ratio of the positive pressure liquid phase modification is 1 to 10 ml / g; Preferably, the time of positive pressure liquid phase modification is 2 to 8 hours.

5. The method for regenerating waste artificial graphite according to claim 1, characterized in that: The manganese source is at least one of manganese nitrate, manganese acetylacetonate, manganese acetate, manganese citrate, manganese tungstate, manganese trifluoromethanesulfonate, manganese gluconate, manganese molybdate, and manganese hypophosphite; Preferably, the metal N source is at least one of nitrate, chloride and oxalate of metal N; Preferably, the carbon source is one or more of glucose, sucrose, organic polymers, starch, etc.; Preferably, the binder is at least one of sodium alginate, polyacrylic acid, polyvinylidene fluoride, carboxymethyl cellulose and gum arabic; Preferably, the mass ratio of the modified material, the manganese source, the metal N source, the carbon source and the binder is 100:0.001-0.2:0.005-0.2:3-8:0.5-2.

6. The method for regenerating waste artificial graphite according to claim 1, characterized in that: The hydrogen-containing atmosphere is a mixture of hydrogen and protective gas; Preferably, the hydrogen content in the hydrogen-containing atmosphere is 2 to 10 v%; Preferably, the temperature of the heat treatment and annealing stage is 500-850°C; Preferably, the heat treatment and annealing treatment are performed for 1 to 6 hours respectively; Preferably, the negative pressure is 200 Pa or less.

7. The method for regenerating waste artificial graphite according to claim 1, characterized in that: The lithium salt includes at least one of lithium chloride, lithium formate, lithium benzoate, lithium oxalate, lithium phosphate, lithium isopropoxide, lithium methoxide, n-butyl lithium, lithium hexafluorophosphate, lithium aluminum hydride, and lithium niobate; Preferably, the second carbon source is at least one of coal tar, petroleum tar, polyvinyl alcohol and polyacrylonitrile; Preferably, the mass ratio of the heat-treated material to the lithium salt, the second carbon source to the lithium source is 100:3-8:0.05-0.2; Preferably, the calcination temperature is 900-1250°C; Preferably, the calcination time is 2 to 8 hours; Preferably, the calcination stage is carried out under positive pressure, and preferably, the positive pressure is 1.5 to 2.5 atm.

8. A regenerated graphite material obtained by the method for regenerating waste artificial graphite according to any one of claims 1 to 7.

9. An application of the regenerated graphite material obtained by the method for regenerating waste artificial graphite according to any one of claims 1 to 7, characterized in that: It is used as negative electrode active material for preparing lithium-ion batteries.

10. A lithium ion battery, characterized in that: The invention relates to a regenerated graphite material obtained by the method for regenerating waste artificial graphite according to any one of claims 1 to 7.

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