Waste graphite repair material as well as preparation method and application thereof

Abstract

The invention relates to the field of waste graphite material recovery, in particular to a waste graphite repair material and a preparation method and application thereof.The preparation method of the waste graphite repair material comprises the steps that waste graphite and a modifier are subjected to thermal modification in an oxygen-containing atmosphere and then subjected to liquid-phase modification treatment in oxidizing acid liquor, and a modified material is obtained; the modifier is a raw material containing chlorine and ammonium; carrying out graphitization treatment on the modified material to obtain a graphitized material; carrying out chemical silver plating treatment on the graphitized material to obtain a silver-plated material; and mixing the silver plating material, the structure modifier and the carbon source, and roasting to obtain the composite material. The material repaired by the method can meet the application requirements of high-surface-load full battery fast charging.

Description

Technical Field

[0001] The invention belongs to the field of waste lithium-ion battery recycling, and specifically relates to the field of graphite recycling and regeneration. Background Art

[0002] With the rapid development of new energy vehicles, the application of lithium-ion batteries has increased year by year. As a commercial lithium-ion battery negative electrode material with relatively stable performance, graphite has a very broad application prospect. As the consumption of lithium-ion batteries increases, the amount of scrapped lithium-ion batteries is also showing a blowout state.

[0003] Current research generally focuses on recycling valuable cathode materials of waste lithium-ion batteries. There are relatively few reports on the recycling of graphite, and it has not yet been mass-produced. With the development of society, new energy vehicles have higher performance requirements, such as high first coulomb efficiency and excellent fast charging characteristics. Therefore, if the recycled graphite can be regenerated into high-performance graphite negative electrode materials, it will be of great significance to promote the green and healthy development of waste lithium-ion batteries.

[0004] There are some recycling and regeneration processes for existing waste graphite in the prior art. For example, the patent document with publication number IN202417073898A discloses a method for preparing battery-grade graphite from battery waste, including: low-temperature roasting and surface modification of mixed waste of positive and negative electrode materials of failed lithium-ion batteries, followed by flotation. For another example, the patent document with publication number CN119208595A discloses a method for recycling and modifying graphite negative electrode materials of failed batteries, wherein the recycled graphite negative electrode materials, silicon oxide and graphene oxide are subjected to a reduction reaction, followed by a recycling process after high-temperature carbonization.

[0005] Although there are some processes for regenerating graphite from waste batteries in the existing technology, it is difficult to effectively reconstruct the damaged short-range ion conduction path of graphite with the existing process, and it is difficult to regenerate materials with fast-charging performance, especially it is difficult to regenerate materials that meet the requirements of high-area-load full-battery fast-charging applications. Summary of the invention

[0006] In view of the problem that the existing waste graphite repair process is difficult to obtain a material that meets the requirements of fast charging of high-area-load full batteries, the first purpose of the present invention is to provide a method for preparing waste graphite repair materials, aiming to effectively reconstruct the damaged short-range conduction network of the waste graphite, and then regenerate a regenerated graphite material that meets the requirements of high-area-load full battery applications.

[0007] The second purpose of the present invention is to provide a waste graphite repair material obtained by the preparation method and its application.

[0008] The third object of the present invention is to provide a lithium ion battery comprising the waste graphite repair material.

[0009] Half-cell and full-cell systems are different, and it is difficult to directly infer their effects. For example, for full-cells, they will face more prominent problems of efficiency, pathways, and stability caused by ion embedding and de-embedding, especially for fast-charging full-cell systems, which face greater technical challenges. In view of the problem that graphite repair materials are difficult to adapt to the requirements of high-surface-load full-cell fast-charging applications, the present invention has been deeply studied and provides the following improvement scheme:

[0010] A method for preparing a waste graphite repair material, comprising: subjecting waste graphite and a modifier to thermal modification in an oxygen-containing atmosphere, and then subjecting the waste graphite to liquid phase modification treatment in an oxidizing acid solution to obtain a modified material; the modifier is a raw material containing chlorine and ammonium radicals;

[0011] The modified material is graphitized to obtain a graphitized material;

[0012] The graphitized material is subjected to chemical silver plating to obtain a silver-plated material;

[0013] Then, the silver-plated material, the structure modifier and the carbon source are mixed and calcined to obtain the waste graphite repair material;

[0014] The structural modifier includes one of lithium titanate, lithium zirconate, lithium niobate, lithium cerate and lithium aluminate.

[0015] The present invention innovatively performs gas-solid modification on waste graphite in the modifier and oxygen-containing atmosphere, and then performs liquid-phase modification in the oxidizing acid solution, and further cooperates with graphitization, chemical plating and structural modifier combined modification treatment, thereby optimizing the purity of graphite, reconstructing the damaged short-range conduction network of waste graphite, and improving the interface and stability of the material. The method described in the present invention can regenerate a repair material that meets the requirements of high-area-load full-battery fast-charging applications.

[0016] In the present invention, the waste graphite is a graphite-containing material obtained by stripping waste batteries.

[0017] Preferably, the content of waste graphite is above 80wt.%.

[0018] In the present invention, the type of the modifier and the combination of the thermal modification under an oxygen-containing atmosphere are the key to optimizing the purity of graphite, unblocking its interlayers and optimizing the surface physical and chemical structure.

[0019] In the present invention, the modifier is ammonium chloride and / or organic ammonium chloride; the structure of the organic ammonium chloride is, for example: The R1 to R4 are independently alkyl groups, and may further be C1 to C20 straight-chain or branched alkyl groups. Furthermore, the organic ammonium chloride may further be at least one of methylammonium chloride, tetrapropylammonium chloride, methyltributylammonium chloride, tetraethylammonium chloride, decanyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride.

[0020] The research of the present invention shows that the use of a modifier that can provide chlorine and ammonium, especially the use of organic ammonium chloride as a modifier, combined with the process of the present invention, can obtain better adaptability and synergy, which is helpful to further optimize the physicochemical characteristics of the repaired material and help to further improve the fast charging performance of the repaired material in a high-surface-load full-battery system.

[0021] Preferably, the oxygen-containing atmosphere is an atmosphere containing oxygen, and further is at least one of oxygen, an oxygen-protective gas mixture, and air.

[0022] Preferably, the weight ratio of waste graphite to modifier is 100:0.1-5; further, it can be 100:1-2.5.

[0023] Preferably, the temperature of the thermal modification is 300 to 500°C, and may further be 400 to 450°C.

[0024] Preferably, the holding time at the thermal modification temperature is 2 to 4 hours.

[0025] In the present invention, the oxidizing acid solution is a solution containing acid and oxidizing components.

[0026] Preferably, the acid is at least one of hydrochloric acid, sulfuric acid and nitric acid.

[0027] Preferably, the oxidizing component includes one or more of perchloric acid, magnesium perchlorate, iron perchlorate, zinc perchlorate, nickel perchlorate, lithium perchlorate, tetramethylammonium perchlorate, and the like.

[0028] Preferably, the hydrogen ion concentration in the oxidizing acid solution is 0.005 to 0.1 M, and further can be 0.01 to 0.05 M. The mass ratio of the oxidizing component to graphite is 0.001 to 0.5:100, and further can be 0.1 to 0.2:100.

[0029] Preferably, the temperature in the liquid phase modification stage is 120-180°C, and further can be 125-155°C.

[0030] Preferably, the liquid phase modification time is 4 to 12 hours, and further can be 6 to 8 hours.

[0031] In the present invention, the graphitization temperature is above 2850°C.

[0032] Preferably, the holding time at the graphitization temperature is 16 to 40 hours, and can further be 18 to 22 hours.

[0033] In the present invention, the graphitized material is silver-plated in advance, which is conducive to combining with other processes to improve the fast charging, initial efficiency and low-temperature stability of the recycled material.

[0034] In the present invention, the graphitized material is placed in a silver plating solution containing anions for chemical plating;

[0035] Preferably, the silver plating solution contains silver ions and an auxiliary agent;

[0036] Preferably, the auxiliary agent includes at least one of citrate, tartrate, formaldehyde, grape bran, etc. Further preferably, the auxiliary agent includes citrate and tartrate in a molar ratio of 1:1 to 2. The citrate and tartrate are at least one of the sodium salt, potassium salt and ammonium salt of their respective organic acids. The innovative research of the present invention shows that the use of the composite auxiliary agent to assist in chemical silver plating can be combined with the process of the present invention, which helps to further optimize the physicochemical structure of the prepared repair material, assist in reconstructing the active sites of ion embedding and de-embedding, reconstruct the conductive network and efficiency, and help improve its fast charging performance in a high-surface-load full-battery system.

[0037] Further preferably, an auxiliary agent is added to the chemical silver plating system, and the auxiliary agent includes one or more of nickel potassium cyanide, nickel acetylacetonate, nickel benzoate, potassium thiocyanate, nickel acetate tetrahydrate, etc. The amount of the auxiliary agent is 1-20wt.% of the weight of the graphitized material, and can further be 5-10wt.%.

[0038] The research of the present invention shows that further adding the auxiliary additive to the chemical silver plating system can further optimize the physical and chemical structure of the repair material, which helps to improve its fast charging performance in a high-surface-load full-battery system.

[0039] In the present invention, the silver content in the silver-plated material can be adjusted as needed, for example, the silver content can be 0.0001 to 0.002 wt %; further, it can be 0.001 to 0.0015 wt %.

[0040] In the present invention, the structural modifier at least comprises lithium niobate. The present invention shows that the preferred structural modifier, in addition to having excellent structural adjustment function, can also be combined with the chemical silver plating process to facilitate the formation of Ag-Nd active site characteristics, and further can further synergistically optimize the low temperature, fast charging and first effect of the repaired material.

[0041] In the present invention, the carbon source includes at least one of asphalt, phenolic resin, petroleum resin and epoxy resin.

[0042] Preferably, the weight ratio of the silver plating material, the structure modifier and the carbon source is 100:0.005-0.2:1-5; preferably 100:0.1-0.15:3-5.

[0043] Preferably, the silver plating material, the structure modifier and the carbon source are mixed by a spraying method.

[0044] Preferably, the calcination temperature is 800-1200°C, and may further be 950-1150°C.

[0045] Preferably, the calcination time is 1 to 6 hours, and further can be 3 to 4 hours.

[0046] The invention also provides a waste graphite repair material prepared by the preparation method.

[0047] The method described in the present invention can give the prepared material special physical and chemical characteristics, and the material with these characteristics can unexpectedly take into account the characteristics of excellent fast charging, ultra-low temperature stability and high initial efficiency.

[0048] The present invention also provides application of the waste graphite repair material prepared by the preparation method, which is used as a negative electrode active material.

[0049] The present invention also provides a lithium ion battery, which comprises the waste graphite repair material obtained by the preparation method.

[0050] The lithium-ion battery of the present invention, in addition to comprising the waste graphite repair material, may have other components and structural relationships that are known.

[0051] Beneficial Effects

[0052] The present invention innovatively performs gas-solid modification on waste graphite in the modifier and oxygen-containing atmosphere, and then performs liquid-phase modification in the oxidizing acid solution, and further cooperates with graphitization, chemical plating and structural modifiers for joint modification treatment, so as to achieve process synergy, optimize the purity of graphite, reconstruct the damaged short-range conduction network of waste graphite, and improve the interface and stability of the material. The method described in the present invention can regenerate a material that can adapt to high-surface-load application requirements and take into account excellent fast charging, low-temperature stability and first-effect.

[0053] In addition, the present invention shows that the optimization of the type of modifier, structure adjustment agent and chemical plating process can further improve the high surface loading performance of the full battery of the prepared material. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a SEM image of the graphite raw material of Example 1;

[0055] Figure 2 is the XRD pattern of the graphite raw material of Example 1;

[0056] Figure 3 This is the SEM image of the graphite material after repair in Example 1;

[0057] Figure 4 This is the XRD diagram of the graphite material after repair in Example 1. DETAILED DESCRIPTION

[0058] The waste graphite described in the present invention can be obtained by stripping conventional scrapped batteries; for example, as an illustrative solution, in the following case, the waste graphite selected is waste graphite material collected from waste lithium-ion batteries.

[0059] An enumerable regeneration scheme of the present invention comprises the following steps:

[0060] (1) Thermal modification

[0061] After the waste graphite and the additive A are uniformly mixed, they are pretreated in an air atmosphere.

[0062] The auxiliary agent A is one or more of ammonium chloride, methyl ammonium chloride, tetrapropyl ammonium chloride, methyl tributyl ammonium chloride, tetraethyl ammonium chloride, decanyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, etc., which are mixed evenly and placed in an air atmosphere at 300-500° C. for oxidation treatment for 2-4 hours; the obtained material is then sieved to obtain particles with a D50 of 6-8 um; the fixed carbon content of the waste graphite is more than 88%, and the mass ratio of the auxiliary agent A to the waste graphite is 0.02-5:100.

[0063] (2) Liquid phase modification

[0064] The graphite powder obtained in the previous step is immersed in a purified liquid for wet treatment under closed conditions. After the reaction is completed, the mixture is cooled to room temperature, and then solid-liquid separation, filter cake washing and drying are performed.

[0065] A mixed system of hydrochloric acid and additive B is used, the concentration of hydrochloric acid is 0.005-0.1M, and additive B refers to one or more of perchloric acid, magnesium perchlorate, iron perchlorate, zinc perchlorate, nickel perchlorate, lithium perchlorate, tetramethylammonium perchlorate, etc.; the mass ratio of additive B to graphite is 0.001-0.5:100. The atmosphere under closed conditions is oxygen, air, ozone, etc.; the treatment temperature is 120-180°C, and the treatment time is 4-12h.

[0066] (3) Graphitization

[0067] The powder obtained in the previous step is placed in a graphitization furnace and graphitized at 2850°C or above.

[0068] The graphitization heat preservation time is 16 to 40 hours.

[0069] (4) Chemical Ag plating

[0070] (5) Structural modification

[0071] The silver-plated powder, structure modifier, and carbon source are dispersed in an alcohol solvent, subjected to ultrasonic treatment, spray-dried, and finally carbonized in an inert atmosphere to obtain the high initial efficiency and fast-chargeable graphite negative electrode. The structure modifier is one of lithium titanate, lithium zirconate, lithium niobate, lithium cerate, and lithium aluminate. The mass ratio of carbon source, structure modifier, and graphite is 1 to 5: 0.005 to 0.2: 100; the heat treatment temperature after spray drying is 800 to 1200°C, and the heat treatment time is 1 to 6 hours.

[0072] In the present invention, the high surface loading positive electrode may refer to a positive electrode with an active material loading of more than 10 mg / cm2, for example, the further surface loading may be 15 to 60 mg / cm2.

[0073] Example 1

[0074] (1) Waste graphite (graphite with a fixed carbon content of 92% obtained by disassembling and initially separating waste lithium batteries) and a modifier (ammonium chloride) were uniformly mixed in a mass ratio of 100:2, and then heated in an air atmosphere at a heating temperature of 400°C for a holding time of 3 hours.

[0075] (2) The graphite powder obtained in the previous step is immersed in 0.01M hydrochloric acid, and 0.2% magnesium perchlorate (based on the weight of the carbon material treated in step 1) is added. The system is sealed in an air atmosphere and placed in an environment at 150°C for 6 hours. Then, solid-liquid separation is performed, and the filter cake is washed and dried.

[0076] (3) The powder obtained in the previous step is placed in a graphitization furnace and graphitized at 2900-3000° C. The graphitization holding time is 20-22 h.

[0077] (4) Chemical Ag plating

[0078] The above materials were placed in a 0.2M silver nitrate aqueous solution, and 0.005M sodium citrate (auxiliary agent 1) and 0.008M sodium tartrate (auxiliary agent 2) were added. After standing for 2 hours, solid-liquid separation was performed to obtain a silver-plated material (the silver content of which was 0.001wt%).

[0079] (5) Structural modification

[0080] The silver-plated powder, structure regulator (lithium niobate) and asphalt are dispersed in ethanol at a mass ratio of 100:0.1:3, subjected to ultrasonic treatment, and then spray-dried; after spray-drying, the temperature is raised to 1100° C. in a protective atmosphere and kept warm for 4 hours to obtain the repaired graphite.

[0081] Example 2

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

[0083] Group A: the modifier is methyltributylammonium chloride; other operations and parameters are the same as those in Example 1;

[0084] Group B: The weight ratio of waste graphite to modifier is 100:1, the heat treatment temperature is 450° C., and the time is 4 h; other operations and parameters are the same as in Example 1.

[0085] Example 3

[0086] Compared with Example 1, the only difference is that in step 2, the concentration of hydrochloric acid in the solution is 0.05M, the oxidizing component is lithium perchlorate, which is 0.1% of the weight of the graphite in step 1, the temperature is 130°C, the time is 8h, and the other operations and parameters are the same as in Example 1.

[0087] Example 4

[0088] Compared with Example 1, the only difference is that the chemical plating conditions in step 4 are changed. The experimental groups are:

[0089] Group A: nickel acetylacetonate was added to 8% of the weight of the graphitized carbon from step 3;

[0090] Group B: In the chemical plating, only additive 1 was included, and the concentration of additive 1 was 0.015M;

[0091] Group C: In the chemical plating, only the auxiliary agent 2 is included, and the concentration of the auxiliary agent 2 is 0.015M; other conditions are the same as those in Example 1.

[0092] Example 5

[0093] Compared with Example 1, the only difference is that the conditions of step 5 are changed, and the experimental groups are:

[0094] Group A: The structural modifier is lithium titanate;

[0095] Group B: silver-plated powder, structure regulator (lithium niobate), asphalt in a mass ratio of 100:0.15:4; temperature 1000℃, time 3h;

[0096] Other operations and parameters are the same as in Example 1.

[0097] Comparative Example 1

[0098] Compared with Example 1, the only difference is that in step 1, sodium chloride is used to replace the ammonium chloride in an equal amount, and other operations and parameters are the same as in Example 1.

[0099] Comparative Example 2

[0100] Compared with Example 1, the only difference is that the atmosphere in step 1 is replaced by nitrogen, and the other operations and parameters are the same as in Example 1.

[0101] Comparative Example 3

[0102] Compared with Example 1, the only difference is that the treatment of step 4 is not performed, and the product of step 3 is directly treated with step 5. Other operations and parameters are the same as those in Example 1.

[0103] Comparative Example 4

[0104] Compared with Example 1, the only difference is that the chemical silver plating of step (4) is not performed, but the graphite material of step 3 is directly mixed with silver powder (the amount of silver powder is the same as that of Example 1) and then the treatment of step 5 is performed. Other operations and parameters are the same as those of Example 1.

[0105] Comparative Example 5

[0106] Compared with Example 1, the only difference is that in step (4), silver nitrate is replaced by an equal amount of sodium nitrate, and other operations and parameters are the same as in Example 1.

[0107] Comparative Example 6

[0108] Compared with Example 1, the only difference is that in step 5, lithium carbonate is used to replace the structure modifier, and the amount of lithium element added in the structure modifier and other operations and parameters are the same as in Example 1.

[0109] test:

[0110] Test 1, 0.2C test is half-battery test

[0111] The graphite prepared in the case was used as the negative electrode. Graphite, Super P, and LA133 were dispersed in deionized water at a mass ratio of 95:2:3 to form a slurry, which was then applied to copper foil and dried to form a negative electrode. The separator was Celegard 2400 membrane. The electrolyte was 1M LiPF6 / EC+DEC+DMC (1:1:1). The counter electrode was a lithium sheet. The lithium half-cell was assembled in a glove box for testing, and its 0.2C first reversible specific capacity and first efficiency were measured.

[0112] Test 2, 6C fast charge test is a full battery test

[0113] The graphite prepared in the example is used as the negative electrode (the same as the negative electrode sheet in test 1).

[0114] NCM positive electrode: The positive electrode materials include LiNi1 / 3Co1 / 3Mn1 / 3O2 (active material), conductive agent (carbon black) and binder (PVDF) in a weight ratio of 9:0.5:0.5; the surface loading of active material in the NCM positive electrode is 50 mg / cm2, the separator is Celegard2400 membrane, and the electrolyte is 1M LiPF6 / EC+DEC+DMC (1:1:1) to prepare a 10Ah soft-pack battery, and its constant current ratio is tested by 6C charging and 1C discharge.

[0115] Table 1

[0116]

[0117] As can be seen from Table 1, the present invention performs gas-solid modification on waste graphite in the modifier and oxygen-containing atmosphere, and then performs liquid-phase modification in the oxidizing acid solution, and further cooperates with graphitization, chemical plating and structural modifier combined modification treatment, so as to achieve process synergy, optimize the purity of graphite, reconstruct the damaged short-range conduction network of waste graphite, and improve the interface and stability of the material. The method described in the present invention can regenerate a material that can adapt to high-surface-load application requirements and take into account excellent fast charging, low-temperature stability and first effect.

[0118] In addition, it can be seen from Examples 1 and 2 that the use of the organic modifier can be combined with the process to obtain better synergy, which helps to further improve the fast charging performance of half-batteries, especially high-surface-load full batteries.

[0119] It can be seen from Examples 1 and 4 that the use of the chemical silver plating process, especially the innovative use of the combined additives and transition metal organics, can optimize the performance of the material at a lower dosage, and in particular can effectively improve the fast charging performance of high-area-load full batteries.

[0120] It can be seen from Examples 1 and 5 that the use of lithium niobate as a structural modifier can construct a certain alloying of niobium and silver, which can further optimize the fast charging performance of the prepared high-area-load full battery.

Claims

1. A method for preparing a waste graphite repair material, characterized in that: The waste graphite and the modifier are subjected to thermal modification in an oxygen-containing atmosphere, and then subjected to liquid phase modification treatment in an oxidizing acid solution to obtain a modified material; The modifier is a raw material containing chlorine and ammonium; The modified material is graphitized to obtain a graphitized material; The graphitized material is subjected to chemical silver plating to obtain a silver-plated material; Then, the silver-plated material, the structure modifier and the carbon source are mixed and calcined to obtain the waste graphite repair material; The structural modifier includes one of lithium titanate, lithium zirconate, lithium niobate, lithium cerate and lithium aluminate.

2. The method for preparing the waste graphite repair material according to claim 1, characterized in that: The waste graphite is a graphite-containing material obtained by stripping waste batteries; Preferably, the content of waste graphite is above 80wt.%.

3. The method for preparing the waste graphite repair material according to claim 1, characterized in that: The modifier is ammonium chloride and / or organic ammonium chloride; the structure of the organic ammonium chloride is: The R1 to R4 are independently alkyl groups; Preferably, the oxygen-containing atmosphere is an atmosphere containing oxygen, further comprising at least one of oxygen, an oxygen-protective gas mixture, and air; Preferably, the weight ratio of waste graphite to modifier is 100:0.1-5; Preferably, the temperature of thermal modification is 300 to 500°C; Preferably, the holding time at the thermal modification temperature is 2 to 4 hours.

4. The method for preparing the waste graphite repair material according to claim 1, characterized in that: The oxidizing acid solution is a solution containing acid and oxidizing components; Preferably, the acid is at least one of hydrochloric acid, sulfuric acid and nitric acid; Preferably, the oxidizing component includes one or more of perchloric acid, magnesium perchlorate, iron perchlorate, zinc perchlorate, nickel perchlorate, lithium perchlorate, tetramethylammonium perchlorate, etc.; Preferably, the hydrogen ion concentration in the oxidizing acid solution is 0.005 to 0.1 M; The mass ratio of the oxidizing component to graphite is 0.001 to 0.5:100; Preferably, the temperature of the liquid phase modification stage is 120 to 180°C; Preferably, the liquid phase modification time is 4 to 12 hours.

5. The method for preparing the waste graphite repair material according to claim 1, characterized in that: The graphitization temperature is above 2850°C; Preferably, the holding time at the graphitization temperature is 16 to 40 hours.

6. The method for preparing the waste graphite repair material according to claim 1, characterized in that: Placing the graphitized material in a silver plating solution containing anions for chemical plating; Preferably, the silver plating solution contains silver ions and an auxiliary agent; Preferably, the auxiliary agent comprises at least one of citrate, tartrate, formaldehyde and grape bran; Preferably, the auxiliary agent comprises citrate and tartrate in a molar ratio of 1:1 to 2; Preferably, an auxiliary agent is further added to the chemical silver plating system, and the auxiliary agent includes one or more of nickel potassium cyanide, nickel acetylacetonate, nickel benzoate, potassium thiocyanate, nickel acetate tetrahydrate, etc.; The dosage of the auxiliary agent is 1-20wt.% of the weight of the graphitized material, and can further be 5-10wt.%.

7. The method for preparing the waste graphite repair material according to claim 1, characterized in that: The structural modifier comprises at least lithium niobate; Preferably, the carbon source comprises at least one of asphalt, phenolic resin, petroleum resin and epoxy resin; Preferably, the weight ratio of the silver plating material, the structure modifier, and the carbon source is 100:0.005-0.2:1-5; Preferably, the silver plating material, the structure modifier, and the carbon source are mixed by a spraying method; Preferably, the calcination temperature is 800-1200°C; Preferably, the calcination temperature is for 1 to 6 hours.

8. A waste graphite repair material obtained by the preparation method according to any one of claims 1 to 7.

9. An application of waste graphite repair material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: It is used as the negative electrode active material.

10. A lithium ion battery, characterized in that: The invention relates to a waste graphite repair material prepared by the preparation method according to any one of claims 1 to 7.

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