Waste graphite-based recycled anode active materials, their preparation and application

Abstract

This invention belongs to the field of waste graphite recycling, specifically relating to a method for preparing a recycled negative electrode active material based on waste graphite. The method involves pre-oxidizing waste graphite material stripped from waste batteries in an oxidizing atmosphere, then placing it in reagent A and performing a first-stage treatment with mechanical assistance. Subsequently, it is mixed with reagent B (added) and sealed in a closed container for a second-stage treatment. Finally, the two-stage treated material is mixed with a carbon source and a transition metal catalyst, shaped, and carbonized, followed by carbon coating to obtain the recycled graphite negative electrode active material. This method significantly improves the fast-charging and intestinal circulation performance of the recycled graphite.

Description

Technical Field

[0001] This invention belongs to the field of waste battery recycling, specifically the field of waste battery negative electrode regeneration. Background Technology

[0002] Lithium-ion batteries are widely used in various fields due to their high energy density, long lifespan, and good safety. However, this has also led to an increase in the amount of scrapped lithium-ion batteries and the issue of their proper disposal. Current research on the recycling of scrap lithium-ion batteries focuses on the positive electrode, with relatively little research on the recycling of graphite negative electrode materials. Most companies treat waste graphite powder as solid waste, which not only wastes graphite resources but also causes environmental pollution.

[0003] Because current waste battery recycling mostly uses sulfuric acid as a leaching agent, and the neutralized water after lime neutralization is returned to the system for reuse, the carbon slag generated from waste lithium-ion battery recycling inevitably contains complex components such as calcium sulfate, nickel and cobalt metal oxides, natural graphite, artificial graphite, carbonaceous conductive agents, and hard carbon formed by membrane carbonization, and may even contain silica dust. Furthermore, during battery dismantling, positive electrode aluminum foil residue is inevitably present in the negative electrode powder, leading to complex purification processes and high purification costs. In addition, the capacity, first-time efficiency, and cycle life of the recycled graphite products are difficult to meet the performance requirements of high-end graphite products. Therefore, for enterprises, the recycling process is long and costly, but the recycling benefits are not ideal, inevitably leading to a sluggish waste graphite recycling market and affecting the efficient reuse of graphite resources. Therefore, new processes are needed to prepare high-performance high-end graphite negative electrodes. Summary of the Invention

[0004] To address the problem that the recycling performance of waste graphite materials from waste batteries is not ideal and it is difficult to adapt to the requirements of high rate and long-range cycling, this invention provides a method for preparing a recycled graphite-based negative electrode active material, aiming to regenerate a recycled graphite negative electrode active material with excellent high rate and long-range cycling performance.

[0005] The second objective of this invention is to provide a regenerated negative electrode active material prepared by the aforementioned method and its application as a negative electrode active material in the preparation of batteries.

[0006] A third objective of this invention is to provide a battery, its negative electrode, and a negative electrode material.

[0007] Graphite materials obtained from the stripping of waste batteries contain many impurities and defects caused by recycling, making it difficult to regenerate them into materials that meet the requirements of fast charging and long cycle life. To address this problem, this invention, through in-depth research, has achieved the following solution:

[0008] A method for preparing a recycled graphite-based negative electrode active material, comprising the following steps:

[0009] Step 1:

[0010] Waste graphite material stripped from waste batteries is pre-oxidized in an oxidizing atmosphere to obtain pre-oxidized material;

[0011] Step 2:

[0012] The pre-oxidized material is placed in reagent A and subjected to the first stage of treatment with mechanical assistance to obtain the first stage of treated material;

[0013] The first stage of treatment material and reagent B are then mixed and sealed in a closed container for the second stage of treatment. After solid-liquid separation, washing and drying, two stages of treatment material are obtained.

[0014] Wherein, reagent A is an aqueous solution containing at least one solute selected from hydroxides, carbonates, and bicarbonates of an alkali metal element; and reagent B contains a compound of formula 1.

[0015]

[0016] In Formula 1, R is a halogen, a C1-C6 alkyl group, a substituted alkyl group, or an alkylamino group;

[0017] The primary or secondary processed material includes large and small particles after screening, wherein the D50 of the large particles is 8-12 μm and the D50 of the small particles is 2-5 μm.

[0018] Step 3:

[0019] The two-stage processed material is mixed with a carbon source and a transition metal catalyst, shaped and carbonized, and then coated with carbon to obtain the regenerated graphite anode active material.

[0020] This invention innovatively pre-oxidizes waste graphite, performs mechanically assisted treatment with reagent A, and combines this with a two-stage carbon coating process. This synergistic effect allows for the highly selective removal of harmful impurities from the graphite, while also optimizing its surface structure, active sites, and stability. The recycled graphite anode material prepared by the method described in this invention exhibits excellent electrochemical performance, particularly improved fast-charging and long-range cycling stability.

[0021] In this invention, the waste battery is a waste battery with graphite as the negative electrode active material; considering market processing value, it can be a widely used waste lithium-ion battery or a waste sodium-ion battery.

[0022] In this invention, the waste graphite material is a negative electrode material obtained by stripping from the negative electrode of a waste battery, containing more than 50 wt.% graphite, and is also permitted to contain at least one of a conductive agent, binder, current collector, and electrolyte. Considering the value of the processing technology, the graphite content in the waste graphite material can be more than 80 wt.%.

[0023] In this invention, the waste graphite material can be obtained by peeling using conventional methods.

[0024] In this invention, waste graphite material is heated in an oxidizing atmosphere to undergo gas-phase pre-oxidation treatment.

[0025] In this invention, the oxidizing atmosphere is an atmosphere containing at least one oxidizing gas selected from oxygen and ozone; more specifically, it can be at least one selected from air, a mixture of oxygen and diluent gas, and a mixture of ozone and diluent gas.

[0026] In this invention, the dilution gas includes at least one of nitrogen and inert gas.

[0027] In this invention, the temperature of the pre-oxidation treatment is 300–600°C, and can be further 330–420°C.

[0028] In this invention, the pre-oxidation treatment time is 2 to 4 hours.

[0029] Preferably, the pre-oxidation process is carried out under UV light irradiation. This invention demonstrates that pre-oxidation under UV irradiation can further optimize the physicochemical structure of waste graphite materials, thus enhancing the combined treatment effect of reagents A and B, and further improving the fast-charging and long-range cycling performance of recycled graphite materials.

[0030] In this invention, the alkali metal element in the solute of reagent A is at least one selected from lithium, sodium, and potassium. Specifically, the solute can be a hydroxide, carbonate, bicarbonate, or other component of the alkali metal element.

[0031] Preferably, the solute is at least one of lithium hydroxide, lithium carbonate, and lithium bicarbonate, and more preferably two or more. This invention demonstrates that using a preferred combination of lithium compounds as the solute, combined with mechanically enhanced first-stage treatment and subsequent second-stage treatment, can further optimize the physicochemical structure of waste graphite and further enhance the fast-charging and long-range cycling performance of the recycled material.

[0032] In this invention, the concentration of the solute in reagent A is 1–5 M, and more preferably 2–3 M;

[0033] In this invention, the liquid-to-solid ratio of reagent A and pre-oxidized material is 2–5 ml / g;

[0034] In this invention, the rotational speed during the mechanically assisted processing stage is 400–800 rpm;

[0035] In this invention, the processing time for the first stage is 8 to 24 hours.

[0036] In this invention, a first-stage processing material is pre-dispersed in water, followed by the addition of the component of Formula 1 for a second-stage processing. This second-stage processing, involving Formula 1, helps optimize impurities on the graphite surface and between layers, and modifies the curing process. This strengthens the physicochemical structure of the surface and between layers, further enhancing the fast-charging and long-cycle performance of the recycled material.

[0037] In this invention, in Formula 1, the halogen in R is, for example, Cl. The alkyl group is, for example, a straight-chain or branched alkyl group. The substituted alkyl group is, for example, a methylene group containing a hydroxyl group, an alkoxy group, or a halogen-substituted group; for example, it can be trifluoromethyl.

[0038] Further, Formula 1 is a composition of Formulas a and b, wherein Formula a is a Formula 1 compound in which R is a halogen, particularly Cl. Formula b is a Formula 1 compound in which R is a substituted alkyl group, particularly a halogen-substituted methylene group. In the composition, the molar ratio of Formulas a and b is, for example, 1:0.5 to 2. Studies have shown that the combination can further achieve synergistic modification, contributing to further enhancing the treatment effect.

[0039] Preferably, in reagent B, the weight ratio of the first-stage treatment material to Formula 1 is 200–90:1, and more preferably 100–150:1.

[0040] Preferably, the temperature of the second processing stage is 20–150°C, and more preferably 25–50°C.

[0041] Preferably, the second stage of processing is carried out under positive pressure; the pressure of the positive pressure is preferably 0.5 to 2 MPa.

[0042] Preferably, the second stage of processing takes 4 to 12 hours, and more preferably 5 to 10 hours.

[0043] In this invention, the first-stage processed material can be screened to obtain large and small particles, and then subjected to a second-stage processing to obtain the graded two-stage processed material. Alternatively, the first-stage processed material can be processed directly into the second-stage processing without screening, and then screened again to obtain the graded two-stage processed material.

[0044] Preferably, the weight ratio of large particles to small particles in the primary or secondary processed material is 100:20 to 50; more preferably, it can be 100:35 to 45.

[0045] In this invention, the carbon source can be any organic material known in the industry that can form carbon, such as resin, and more preferably one or more of polypropylene, polyvinyl chloride, polystyrene, and polyoxymethylene.

[0046] Preferably, the transition metal catalyst comprises a compound of at least one transition metal element selected from nickel, cobalt, and manganese; more preferably, it is a nickel-containing compound.

[0047] Preferably, the weight ratio of the secondary treatment material to the carbon source and the transition metal catalyst is 100:8-15:0.5-2, and more preferably 100:10-12:1-1.5.

[0048] The molding method can be compression molding.

[0049] Preferably, the carbonization temperature is 900–1350°C, and more preferably 1100–1250°C.

[0050] Preferably, the carbonization stage is carried out under negative pressure. The pressure of the negative pressure can be, for example, below 100 Pa.

[0051] Preferably, the carbonization time is 4 to 12 hours, and more preferably 8 to 10 hours.

[0052] Preferably, the carbonization product is combined with the second carbon source and then added for carbon coating treatment.

[0053] In this invention, the second carbon source can be an organic compound known in the industry, such as at least one of a solid-phase carbon source, a liquid-phase carbon source, and a gaseous-phase carbon source. The solid-phase carbon source is a solid organic compound. The liquid-phase carbon source is, for example, an organic compound that is liquid at the stated temperature, or a solution of an organic compound, such as asphalt. The gaseous-phase carbon source is another organic compound that is in the form of carbon during the heat treatment stage, such as C1-C4 alkanes, alkenes, etc.

[0054] Preferably, the temperature of the carbon coating treatment stage is 1050–1250°C; the holding time at this temperature is 4–8 hours.

[0055] The present invention also provides a recycled negative electrode active material based on waste graphite prepared by the aforementioned preparation method.

[0056] The method described in this invention can endow the obtained product with special physicochemical characteristics, and the recycled material obtained by the method can unexpectedly exhibit excellent performance, especially excellent fast charging and long-range cycling effects.

[0057] This invention also provides the application of the waste graphite-based regenerated negative electrode active material prepared by the above-described preparation method, which is used as a negative electrode active material for the preparation of alkali metal ion batteries.

[0058] In this invention, the regenerated negative electrode active material can be used as the negative electrode active material, and the desired alkali metal ion battery and its components can be prepared based on existing conventional means and methods.

[0059] In this invention, the alkali metal ion battery is a lithium-ion battery or a sodium-ion battery.

[0060] The present invention also provides a negative electrode for an alkali metal battery, comprising a recycled graphite-based negative electrode active material prepared by the aforementioned method.

[0061] The present invention also provides an alkali metal battery comprising the negative electrode described herein.

[0062] The alkali metal battery and its negative electrode described in this invention, except for the recycled graphite-based negative electrode active material described in this invention, can have other conventional components and structural parts.

[0063] Beneficial effects

[0064] This invention innovatively pre-oxidizes waste graphite, performs mechanically assisted treatment with reagent A, and combines this with a two-stage carbon coating process. This synergistic effect allows for the highly selective removal of harmful impurities from the graphite, while also optimizing its surface structure, active sites, and stability. The recycled graphite anode material prepared by the method described in this invention exhibits excellent electrochemical performance, particularly improved fast-charging and long-range cycling stability. Attached Figure Description

[0065] Figure 1 Here is a SEM image of the waste graphite from Example 1;

[0066] Figure 2 Here is a SEM image of the recycled graphite material treated in Example 1;

[0067] Figure 3 The graph shows the lithium half-cell cycle performance (0.2C) of the product obtained in Example 1.

[0068] Figure 4 The graph shows the cycling performance of the product obtained in Example 1 against a lithium half-cell (first 5 cycles at 0.2C, then 1000 cycles at 1C). Detailed Implementation

[0069] The waste graphite described in this invention can be obtained by peeling off waste graphite electrodes from waste batteries. The peeling method can be conventional, such as solvent peeling, thermal peeling, etc.

[0070] In this invention, the waste graphite material obtained through stripping, in addition to mainly containing graphite, is also allowed to contain trace amounts of conductive agents, binders, diaphragms, electrolytes, etc. Considering the recycling value of the technical solution, the graphite content can be above 50 wt%. The following examples, as typical embodiments that can be listed, show a content between 80 and 90 wt%.

[0071] This invention provides an optional method for preparing recycled graphite-based anode active materials, comprising the following steps:

[0072] Step 1: Pre-treat the waste graphite carbon slag in an oxidizing atmosphere;

[0073] Step 2: Place the obtained carbon oxide slag in an aqueous solution of reagent A, perform wet ball milling, then wash the slurry, filter, dry the filter cake, and break it up to obtain a first-stage processed material. The first-stage processed material can be large and small particles that have been screened and graded.

[0074] Step 3: Add the first stage of the processed material to the solution containing reagent B of Formula 1, carry out the stirring reaction under closed conditions, then wash the pulp, filter, dry the filter cake, and break it up to obtain the second stage of the processed material.

[0075] It should be noted that step 2 can also skip screening and proceed directly to step 3. After the third step is completed, screening is performed to separate the material into large and small particles according to the specified gradation, thus obtaining the two-stage processed material.

[0076] The median particle size D50 of the small particles and large particles are 3-5 μm and 8-12 μm, respectively. The mixing ratio of small particles to large particles is 20-50:100.

[0077] Step 4: Mix the two-stage processed powder according to a certain ratio, add a certain amount of resin and nickel salt, heat and mix in a kneader, press and mold, then vacuum carbonize, break up and sieve.

[0078] Step 5: The obtained powder is carbon-coated, dispersed, demagnetized, and sieved to obtain the graphite anode powder.

[0079] In step 1 of the present invention, the oxidizing atmosphere refers to a gas containing one or two of air, oxygen, and ozone, and the residual gas is one or more of nitrogen, argon, and helium; wherein the volume fraction of air is 50-100%, the volume fraction of oxygen is 10-50%, and the volume fraction of ozone is 0.5-10%.

[0080] The processing temperature in step 1 is 300–600℃, and the holding time is 2–4 hours.

[0081] In step 2 of this invention, reagent A is one or more of lithium, sodium, potassium hydroxide, carbonate, or bicarbonate, preferably a mixture of sodium hydroxide and sodium carbonate. The concentration of the aqueous solution of A is 2-5 M; the liquid-to-solid ratio of the aqueous solution of A to the carbon dioxide slag is 2-5 ml / g; the ball milling speed is 400-800 rpm; and the ball milling time is 8-24 h.

[0082] In step 4, the resin refers to one or more of polypropylene, polyvinyl chloride, polystyrene, and polyoxymethylene; the ratio of resin to carbon powder (second-stage material) is 8-15:100; the nickel salt is one or more of nickel oxalate, nickel hydroxide, nickel acetylacetone, nickel acetate, nickel phthalocyanine, nickel carbonate, and basic nickel carbonate, and the ratio of nickel salt to carbon powder is 0.5-2:100; the vacuum carbonization is performed by placing the molding material in a vacuum furnace, introducing one or more of nitrogen, argon, and helium for gas exchange, then gradually heating it to 900-1350℃, and then evacuating it under vacuum, maintaining the system at 20-200 Pa, and holding it at this temperature for 4-12 hours before naturally cooling it to room temperature.

[0083] The carbon coating process described in step 5 refers to the mixing of asphalt and carbon materials, with an asphalt-to-carbon material ratio of 5-8:100. After the mixture is homogeneous, it is heat-treated to 1050-1250℃ under a protective atmosphere and kept at that temperature for 4-8 hours.

[0084] The following is the specific implementation plan:

[0085] Example 1

[0086] Step 1: Place the waste graphite carbon slag in an oxidizing atmosphere (air) and pre-treat it at 400℃ for 2 hours;

[0087] Step 2: Place the carbon oxide slag obtained in Step 1 into an aqueous solution of reagent A (1M sodium carbonate solution, 1M sodium hydroxide solution, liquid-solid ratio of 3ml / g) and perform wet ball milling at a speed of 600±50rpm for 12h. Then wash the slurry, filter, dry the filter cake, and break it up to obtain the ball milling material.

[0088] The ball milling material was sieved to obtain particles A with a D50 of 4.1 μm and particles B with a D50 of 10.3 μm; and particles A and B were graded in a weight ratio of 30:100 to obtain a first-stage processed material.

[0089] Step 3: Slurry a portion of the treatment material with water at a liquid-to-solid ratio of 5 ml / g and place it in a sealed container. Then add Formula 1 (Formula 1-A in this case). The weight ratio of the first-stage processed material is 1:150. Then, the container is sealed and stirred at a speed of 100-150 rpm and a temperature of 40±5℃ for 6 hours. The pulp is then washed, filtered, the filter cake is dried and broken up to obtain the second-stage processed material.

[0090] Step 4: The second-stage treatment material, resin (polypropylene in this case), and catalyst (nickel acetate in this case) are heated, mixed, and pressed into shape in a kneader at a weight ratio of 100:10:1. Then, the mixture is vacuum carbonized for 10 hours under a pressure of less than 100 Pa and a temperature of 1150±10℃ to obtain carbonized material.

[0091] Step 5: Mix the carbonized material and asphalt from Step 4 at a weight ratio of 100:6 and keep them at a temperature of 1100±10℃ for 6 hours for carbon coating. Then, break them up, demagnetize them, and sieve them to obtain the recycled graphite negative electrode active material.

[0092] Electrochemical performance testing methods:

[0093] A certain amount of recycled graphite anode active material, binder (LA-133, CMC), and conductive carbon black (SP) were uniformly mixed in a mass ratio of 92:3:3:2. Then, anhydrous ethanol and deionized water (volume ratio of 1:3) were added to form a uniform slurry. This slurry was coated onto copper foil and vacuum dried at 120℃ for 12 hours to obtain a graphite anode carrying capacity of 8–12 mg / cm³. 2 Electrode plates.

[0094] Using a CR2025 coin cell casing, with the obtained graphite negative electrode as the working electrode and a lithium metal sheet as the counter electrode, a Celgard 2400 separator, nickel foam as the current collector on the counter electrode side, and a solution containing 1M LiPF6 of ethylene carbonate + dimethyl carbonate + diethyl carbonate (EC + DMC + DEC, volume ratio 1:1:1) as the electrolyte, the cells were assembled in a glove box under an argon atmosphere and then sealed using a sealing machine to obtain a coin cell lithium battery.

[0095] Battery cycle performance was tested at room temperature, with a test voltage range of 0.01V to 1.5V and test rates of 0.2C, 1C, and 10C.

[0096] Example 2

[0097] Compared to Example 1, the only difference is that the conditions in step 1 are changed. The experimental group is as follows:

[0098] Group A: The heat preservation pretreatment stage was carried out under 254nm UV light irradiation.

[0099] Group B: The oxidizing atmosphere is oxygen, the temperature of the heat preservation pretreatment stage is 350℃, and the heat preservation time is 3h;

[0100] All other operations, parameters, and tests are the same as in Example 1.

[0101] Example 3

[0102] Compared to Example 1, the only difference is that the conditions in step 2 are changed. The experimental group is as follows:

[0103] Group A: In reagent A, sodium carbonate was replaced with an equimolar amount of lithium carbonate, and sodium hydroxide was replaced with an equimolar amount of lithium hydroxide. All other operations and parameters were the same as in Example 1.

[0104] Group B: In reagent A, the concentration of sodium carbonate is 0.5M, the concentration of sodium hydroxide is 2M, the ball milling speed is 700±50rpm, the ball milling time is 14h, and after ball milling, particles A with a D50 of 3.6μm and particles B with a D50 of 9.6μm are obtained by sieving; and particles A and particles B are graded at a weight ratio of 40:100 to obtain a first-stage processed material;

[0105] All other operations, parameters, and tests are the same as in Example 1.

[0106] Example 4

[0107] Compared to Example 1, the only difference is that the conditions in step 3 were changed, and the experimental groups were as follows:

[0108] Group A: Equation 1 is Equation 1-B, and its structure is as follows:

[0109] Group B: Formula 1 is a mixture of Formula 1-A and Formula 1-B in a molar ratio of 1:1;

[0110] Group C: Based on Group B, pressurization is carried out during the treatment stage, with a pressurization pressure of 1 MPa;

[0111] Group D: The first-stage treatment material was slurried with water at a liquid-to-solid ratio of 4 ml / g and placed in a sealed container. Then, Formula 1 (the weight ratio of Formula 1 to the first-stage treatment material was 1:100) was added. The container was then sealed and stirred at a speed of 100-150 rpm and a temperature of 35±5℃ for 8 hours. The pulp was then washed, filtered, the filter cake was dried, and the mixture was broken up to obtain the second-stage treatment material.

[0112] All other operations and parameters are the same as in Example 1.

[0113] Example 5

[0114] Compared with Example 1, the only difference is that the ball milling material in step 2 is pretreated with reagent B in step 3, and then washed, filtered, dried and dispersed, and then sieved and graded to obtain a two-stage processed material with a weight ratio of 30:100 of particles A with a D50 of 4.0 μm and particles B with a D50 of 10.4 μm; and then it is subjected to subsequent processing.

[0115] All other operations and parameters are the same as in Example 1.

[0116] Example 6

[0117] Compared with Example 1, the only difference is that the conditions of steps 4 and 5 are changed. Specifically, in step 4: the two-stage processed material, resin (polystyrene in this case), and catalyst (nickel oxalate in this case) are heated, mixed, and pressed into shape in a kneader at a weight ratio of 100:12:1.5, and then vacuum carbonized for 8 hours under a vacuum pressure of less than 100 Pa and a temperature of 1200±10°C to obtain carbonized material.

[0118] Step 5: Mix the carbonized material and asphalt from Step 4 at a weight ratio of 100:5 and keep it at a temperature of 1200±10℃ for 4 hours to carbonize it. Then, break it up, demagnetize it, and sieve it to obtain the recycled graphite negative electrode active material.

[0119] All other operations, parameters, and tests are the same as in Example 1.

[0120] Comparative Example 1

[0121] Compared with Example 1, the only difference is that the waste graphite was not processed in the first step, but was directly used as raw material in the second step and subsequent processes. All other operations, parameters and tests are the same as in Example 1.

[0122] Comparative Example 2

[0123] Compared with Example 1, the only difference is that in step 2, reagent A is replaced with water and the solute is not added. All other operations and parameters are the same as in Example 1.

[0124] Comparative Example 3

[0125] Compared with Example 1, the only difference is that in step 2, no grading and gradation treatment was performed, and the ball milling material was directly used as raw material for step 3 and subsequent processing. All other operations and parameters are the same as in Example 1.

[0126] Comparative Example 4

[0127] Compared with Example 1, the only difference is that in step 3, Formula 1 is not added, while other operations and parameters are the same as in Example 1.

[0128] Comparative Example 5

[0129] Compared with Example 1, the only difference is that in step 3, hydrochloric acid is used to replace the formula 1 (the molar amount of Cl is the same), and all other operations and parameters are the same as in Example 1.

[0130] Comparative Example 6

[0131] Compared to Example 1, the only difference is that in step 3, equimolar amounts are used. Replace Equation 1 as described above, and keep all other operations and parameters the same as in Example 1.

[0132] Comparative Example 7

[0133] Compared to Example 1, the only difference is that the product from step 1 is directly processed in step 3, then the product from step 3 is processed in step 2, and then the product from step 2 is processed in step 4 and subsequent steps.

[0134] All other operations and parameters are the same as in Example 1.

[0135] The electrochemical performance test results for each case are shown in Tables 1 and 2.

[0136] Table 1

[0137]

[0138]

[0139] Table 2

[0140]

[0141] As can be seen from the examples and comparative examples, the process described in this invention can significantly optimize the physicochemical structure of recycled materials and improve their fast charging and long cycle performance.

Claims

1. A method for preparing a recycled negative electrode active material based on waste graphite, characterized in that the steps include: include: Step 1: Waste graphite material stripped from waste batteries is pre-oxidized in an oxidizing atmosphere to obtain pre-oxidized material; Step 2: The pre-oxidized material is placed in reagent A and subjected to the first stage of treatment with mechanical assistance to obtain the first stage of treated material; The first stage of treatment material and reagent B are then mixed and sealed in a closed container for the second stage of treatment. After solid-liquid separation, washing and drying, two stages of treatment material are obtained. Wherein, reagent A is an aqueous solution containing at least one solute selected from hydroxides, carbonates, and bicarbonates of an alkali metal element; and reagent B contains a compound of formula 1. Formula 1 In Formula 1, R is a halogen, a C1-C6 alkyl group, a substituted alkyl group, or an alkylamino group; The primary or secondary processed material includes large and small particles after screening, wherein the D50 of the large particles is 8-12 μm and the D50 of the small particles is 2-5 μm. Step 3: The two-stage processed material is mixed with a carbon source and a transition metal catalyst, shaped and carbonized, and then coated with carbon to obtain the waste graphite-based regenerated negative electrode active material.

2. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The waste batteries mentioned are waste batteries with graphite as the negative electrode active material.

3. The method for preparing the recycled graphite-based negative electrode active material as described in claim 2, characterized in that, The waste batteries mentioned are waste lithium-ion batteries or waste sodium-ion batteries.

4. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The waste graphite material is a negative electrode material obtained by stripping it from the negative electrode of a waste battery, and it contains more than 50 wt.% graphite.

5. The method for preparing the recycled graphite-based negative electrode active material as described in claim 4, characterized in that, The waste graphite material also contains at least one of the following: conductive agent, binder, current collector, and electrolyte.

6. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, An oxidizing atmosphere is an atmosphere containing at least one oxidizing gas, namely oxygen or ozone.

7. The method for preparing the recycled graphite-based negative electrode active material as described in claim 6, characterized in that, The oxidizing atmosphere is at least one of air, a mixture of oxygen and diluent gas, or a mixture of ozone and diluent gas.

8. The method for preparing the recycled graphite-based negative electrode active material as described in claim 7, characterized in that, The dilution gas is an inert gas.

9. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The temperature for pre-oxidation treatment is 300–600°C.

10. The method for preparing the recycled graphite-based negative electrode active material as described in claim 9, characterized in that, The pre-oxidation treatment time is 2 to 4 hours.

11. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The pre-oxidation process is carried out under UV light irradiation.

12. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The alkali metal element in the solute of reagent A is at least one of lithium, sodium, and potassium.

13. The method for preparing the recycled graphite-based negative electrode active material as described in claim 12, characterized in that, The solute is at least one of lithium hydroxide, lithium carbonate, and lithium bicarbonate.

14. The method for preparing the recycled graphite-based negative electrode active material as described in claim 12, characterized in that, The concentration of the solute in reagent A is 1~5M.

15. The method for preparing the recycled graphite-based negative electrode active material as described in claim 12, characterized in that, The liquid-to-solid ratio of reagent A and pre-oxidized material is 2-5 ml / g.

16. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The rotation speed during the mechanical auxiliary processing stage is 400–800 rpm.

17. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The first stage of processing takes 8–24 hours.

18. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The first stage of treatment material is pre-dispersed in water, and then the components of Formula 1 are added for the second stage of treatment.

19. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, In Formula 1, R is Cl, trifluoromethyl, dialkylamino, or tert-butyl.

20. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, In reagent B, the weight ratio of the first-stage treatment material to Equation 1 is 200~90:

1.

21. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The temperature for the second stage of processing is 20~150℃.

22. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The second stage of treatment is carried out under positive pressure.

23. The method for preparing the recycled graphite-based negative electrode active material as described in claim 22, characterized in that, The positive pressure is 0.5~2MPa.

24. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The second stage of processing takes 4 to 12 hours.

25. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The material is screened in the first stage to obtain large and small particles, and then processed in the second stage; or, the material is not screened in the first stage and is directly processed in the second stage, and then screened again to obtain the material processed in the second stage.

26. The method for preparing the recycled graphite-based negative electrode active material as described in claim 25, characterized in that, The weight ratio of large particles to small particles in the primary or secondary processed material is 100:20~50.

27. The method for preparing the recycled graphite-based negative electrode active material as described in claim 26, characterized in that, The weight ratio of large particles to small particles in the primary or secondary processed material is 100:35~45.

28. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The carbon source is resin.

29. The method for preparing the recycled graphite-based negative electrode active material as described in claim 28, characterized in that, The carbon source is at least one of polypropylene, polyvinyl chloride, polystyrene, and polyoxymethylene.

30. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The transition metal catalyst includes a compound of at least one transition metal element selected from nickel, cobalt, and manganese.

31. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The weight ratio of the two-stage treatment material to the carbon source and transition metal catalyst is 100:8~15:0.5~2.

32. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The molding method is compression molding.

33. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The carbonization temperature is 900–1350°C.

34. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The carbonization stage is carried out under negative pressure.

35. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The carbonization time is 4~12 hours.

36. The method for preparing the recycled negative electrode active material based on waste graphite as described in claim 1, characterized in that, The carbonization product is combined with a second carbon source and then added for carbon coating treatment.

37. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The second carbon source is at least one of solid-phase carbon source, liquid-phase carbon source, and gas-phase carbon source.

38. The method for preparing the recycled graphite-based negative electrode active material as described in claim 1, characterized in that, The temperature during the carbon coating process is 1050–1250°C; the holding time at this temperature is 4–8 hours.

39. A recycled graphite-based negative electrode active material prepared by the preparation method according to any one of claims 1 to 38.

40. The application of a recycled graphite-based negative electrode active material prepared by the preparation method according to any one of claims 1 to 38, characterized in that, It is used as a negative electrode active material in the preparation of alkali metal ion batteries.

41. The application as described in claim 40, characterized in that, The alkali metal ion battery mentioned is a lithium-ion battery or a sodium-ion battery.

42. A negative electrode for an alkali metal battery, characterized in that, The invention comprises the waste graphite-based regenerated negative electrode active material prepared by the preparation method according to any one of claims 1 to 38.

43. An alkali metal battery, characterized in that, It includes the negative electrode as described in claim 42.

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