Regeneration method and application of graphite negative electrode of waste lithium ion battery

Abstract

The invention discloses a regeneration method and application of a graphite negative electrode of a waste lithium ion battery, and belongs to the technical field of lithium battery recovery. The method comprises the following steps: performing ultrasonic stripping treatment on a waste graphite pole piece to obtain waste graphite powder, performing high-temperature annealing treatment on the waste graphite powder, slowly heating through the annealing treatment, and keeping at a constant temperature; the preparation method comprises the following steps: adding lithium metal and an anion ligand containing a functional group into a 2-methyltetrahydrofuran solvent, and fully dissolving by stirring to obtain a pre-lithiation reagent containing the functional group; and uniformly stirring the graphite powder subjected to high-temperature annealing treatment and a pre-lithiation reagent containing a functional group, heating while stirring until drying, and grinding the dried product to obtain the regenerated graphite powder for making up the loss of active lithium caused by charging and discharging. The method is simple in step, resources are saved, and the electrochemical performance of the regenerated graphite pole piece is excellent.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium battery recycling, in particular to a waste lithium ion battery graphite negative electrode regeneration method and application. BACKGROUND

[0002] Lithium ion batteries have become one of the most widely used energy storage devices due to their high energy density and long cycle life, and graphite is one of the most common negative electrode materials. However, due to the limited service life of lithium ion batteries, the amount of waste lithium ion batteries is also increasing year by year, and waste graphite negative electrodes are the main environmental pollutants, so it is urgent to recycle and reuse the waste graphite negative electrodes of lithium ion batteries.

[0003] The existing recycling technology for negative electrode materials is not perfect, and the recycling methods are usually through chemical reagents, pre-lithiation technology and high-temperature treatment; the prior art with the publication number CN115954572A discloses a lithium battery graphite negative electrode regeneration method, which comprises the following steps: S1: drying and screening the recycled lithium battery waste graphite negative electrode powder; S2: baking the graphite powder at 550 DEG C in an air atmosphere, and keeping warm for 3h high-temperature oxidation; S3: mixing the oxidized graphite with inorganic acid according to the liquid-solid ratio (mass ratio) 5-10:1 and reacting for 0.5-2h, and then filtering, washing with deionized water and drying to obtain graphite powder; S4: dissolving the carbon source in an organic solvent, and controlling the liquid-solid ratio (mass ratio) of the organic solvent and the carbon source to be 5-10:1; S5: liquid phase coating is carried out on the graphite powder, and the regenerated graphite negative electrode is obtained after graphitization in an inert atmosphere. It needs to use inorganic acid, which is high in cost and pollutes the environment. SUMMARY

[0004] The application aims to overcome the deficiencies in the prior art, and provides a waste lithium ion battery graphite negative electrode regeneration method, which is simple in process and good in waste graphite powder regeneration effect.

[0005] Technical scheme: In order to achieve the above-mentioned purpose, the application discloses a waste lithium ion battery graphite negative electrode regeneration method, and the steps are as follows: S1, the waste graphite electrode sheet is subjected to ultrasonic stripping treatment to obtain waste graphite powder, and the waste graphite powder is subjected to high-temperature annealing treatment, which slowly increases the temperature, keeps constant temperature, reduces the impurity residues in the waste graphite powder, repairs the crystal lattice structure of the graphite, and eliminates the thickened solid electrolyte interface film; S2, lithium metal and anion ligand containing a functional group are added to 2-methyltetrahydrofuran solvent and fully dissolved by stirring to obtain a pre-lithiation reagent containing a functional group; S3, the graphite powder after high-temperature annealing treatment is stirred uniformly with the pre-lithiation reagent containing functional groups, then heated at 50-60℃ while stirring until dry, the dried product is ground to obtain regenerated graphite powder to compensate for the loss of active lithium caused by discharge.

[0006] Further, the waste graphite pole piece includes: waste natural graphite pole piece, waste artificial graphite pole piece, waste block graphite pole piece, waste flake graphite pole piece, waste sandstone graphite pole piece, waste electrode graphite pole piece, waste spherical graphite pole piece, waste expanded graphite pole piece, waste nano graphite pole piece, waste low-impurity graphite pole piece.

[0007] Further, during the high-temperature annealing treatment of the waste graphite powder: the highest temperature of annealing is 600-1500℃, the slow heating rate is 5℃ / min, and the constant temperature is maintained for 2 hours at the corresponding highest temperature.

[0008] Further, the anionic ligand containing functional groups includes one or more of 4-cyanobiphenyl, 1,4-dicyanonaphthalene, 2,7-dicyanonaphthalene, 2,3-dicyanonaphthalene, 1-amino-2-cyanonaphthalene, 9-cyananthracene, 9,10-dicyanoanthracene, 2-methoxybiphenyl, 3-methoxybiphenyl, 4-methoxybiphenyl, 4,4-dimethoxybiphenyl, 3,3'-dimethoxybenzidine, 3-amino-4-methoxybiphenyl, 1-methoxynaphthalene, 2-methoxynaphthalene, 4,4'-dimethoxyoctafluorobiphenyl, 4,4'-diaminooctafluorobiphenyl, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2,2'-diaminobiphenyl, 1,4-diaminonaphthalene, 2,3-diaminonaphthalene, 1,8-diaminonaphthalene, 1,5-diaminonaphthalene, 2,7-diaminonaphthalene, 1,2-diaminonaphthalene.

[0009] Further, the molar ratio of lithium metal to anionic ligand containing functional groups in 2-methyltetrahydrofuran solvent is 1:1, the concentration of pre-lithiation reagent containing functional groups is ensured to be 0.2mol / L-2mol / L, and lithium metal, anionic ligand containing functional groups and 2-methyltetrahydrofuran do not require specific ratio, only need to ensure sufficient dissolution; In order to make lithium metal and anionic ligand containing functional groups fully dissolved in 2-methyltetrahydrofuran solvent, it needs to be stirred continuously for 1 hour: the first 30 minutes are stirred at 40℃, 850rpm, to make the thin sheet-shaped lithium metal dissolve into fine fragments, the last 30 minutes are stirred at 450rpm without heating, to make the lithium metal dissolve better.

[0010] Further, the graphite powder after high-temperature annealing treatment is stirred uniformly with the pre-lithiation reagent containing functional groups according to a mass ratio of 4:3.

[0011] The application relates to a lithium ion battery graphite negative electrode sheet prepared by a recycling method of waste lithium ion battery graphite negative electrodes, wherein the recycled graphite powder is further dried, electrolyte is added dropwise, and the lithium ion battery graphite negative electrode sheet is obtained through coating.

[0012] The application relates to an application of a lithium ion battery graphite negative electrode sheet, and the steps are as follows: A. Preparing a functional pre-lithiation electrolyte: in an argon environment, ethylene carbonate and diethyl carbonate are mixed according to a volume ratio of 55:45, then 1.5 mol / L lithium hexafluorophosphate solution of Merck is added into the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; a pre-lithiation reagent containing a functional group is fully mixed with the electrolyte to obtain the functional pre-lithiation electrolyte, and the volume ratio of the pre-lithiation reagent containing the functional group to the electrolyte is 1:4;

[0013] B. After 5ml of the functional pre-lithiation electrolyte is added dropwise on the lithium ion battery graphite negative electrode sheet, the lithium ion battery graphite negative electrode sheet is assembled into a battery, the functional pre-lithiation electrolyte is used to continuously supply lithium for the battery, and the pressure of a tablet press for assembling the battery is 350-750 kg / cm 2 .

[0014] Beneficial effects: the waste graphite powder is subjected to high-temperature annealing treatment, the impurity residues in the waste graphite powder are reduced, the crystal lattice structure of the graphite is repaired, and the thickened solid electrolyte interface film is eliminated; the recycled graphite powder is fully and uniformly lithiated through the prepared pre-lithiation reagent treatment, the crystal lattice of the recycled graphite electrode sheet is recovered, the interface film is compact, the Coulomb efficiency of the prepared battery is high, the recycling method provided by the application is simple in steps, resources are saved, and the electrochemical performance of the recycled graphite electrode sheet is superior.

[0015] Drawings of the specification

[0016] Figure 1 A first circle charge-discharge curve diagram in electrochemical test of a button-type half battery assembled by a recycled natural graphite electrode prepared in the application example 1.

[0017] Figure 2 A long cycle diagram in electrochemical test of the button-type half battery assembled by the recycled natural graphite electrode prepared in the application example 1.

[0018] Figure 3 A Li + diffusion coefficient diagram in the discharge stage of the recycled natural graphite electrode prepared in the application example 1.

[0019] Figure 4 A Li + diffusion coefficient diagram in the charge stage of the recycled natural graphite electrode prepared in the application example 1.

[0020] Figure 5First cycle charge-discharge curve plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 2 of the present invention.

[0021] Figure 6 Long cycle plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 2 of the present invention.

[0022] Figure 7 Li diffusion coefficient plot for the discharge phase of the regenerated natural graphite electrode prepared in Example 2 of the present invention. +

[0023] Figure 8 Li diffusion coefficient plot for the charge phase of the regenerated natural graphite electrode prepared in Example 2 of the present invention. +

[0024] Figure 9 First cycle charge-discharge curve plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 3 of the present invention.

[0025] Figure 10 Long cycle plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 3 of the present invention.

[0026] Figure 11 Li diffusion coefficient plot for the discharge phase of the regenerated natural graphite electrode prepared in Example 3 of the present invention. +

[0027] Figure 12 Li diffusion coefficient plot for the charge phase of the regenerated natural graphite electrode prepared in Example 3 of the present invention. +

[0028] Figure 13 First cycle charge-discharge curve plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 4 of the present invention.

[0029] Figure 14 Long cycle plot for the electrochemical test of the coin-type half cell assembled with the regenerated natural graphite electrode prepared in Example 4 of the present invention.

[0030] Figure 15 Li diffusion coefficient plot for the discharge phase of the regenerated natural graphite electrode prepared in Example 4 of the present invention. +

[0031] Figure 16 Li diffusion coefficient plot for the charge phase of the regenerated natural graphite electrode prepared in Example 4 of the present invention. +

[0032] Figure 17 ​​​​​​The first circle charge-discharge curve graph of the electrochemical test of the assembled button-type half cell of the regenerated natural graphite electrode prepared in Embodiment 5 of the present application is shown in the following figure.

[0033] Figure 18 The long cycle graph of the electrochemical test of the assembled button-type half cell of the regenerated natural graphite electrode prepared in Embodiment 5 of the present application is shown in the following figure.

[0034] Figure 19 The Li diffusion coefficient graph of the discharge stage of the regenerated natural graphite electrode prepared in Embodiment 5 of the present application is shown in the following figure. +

[0035] Figure 20 The Li diffusion coefficient graph of the charge stage of the regenerated natural graphite electrode prepared in Embodiment 5 of the present application is shown in the following figure. + DETAILED DESCRIPTION

[0036] The embodiments of the present application are further described below in conjunction with the accompanying drawings: Embodiment 1: The present embodiment provides a method for regenerating graphite negative electrode of waste lithium ion battery, the steps are as follows: The waste natural graphite electrode sheet is subjected to ultrasonic stripping treatment to obtain waste natural graphite powder, and the waste natural graphite powder is subjected to high-temperature annealing treatment, the temperature is raised to 600 DEG C at a rate of 5 DEG C / min, and kept at 600 DEG C for 2 hours; The prelithiation reagent containing functional groups is prepared by dissolving lithium metal and 4-cyanobiphenyl in 2-methyltetrahydrofuran solvent to obtain a prelithiation reagent containing functional groups, and the concentration is 0.2 mol / L; The functional prelithiation electrolyte is prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 55:45 in an argon environment, then adding 1.5 mol / L Merck lithium hexafluorophosphate solution to the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; the prelithiation reagent containing 4-cyanobiphenyl is fully mixed with the electrolyte to obtain a functional prelithiation electrolyte, and the volume ratio of the prelithiation reagent containing functional groups to the electrolyte is 1:4; The natural graphite powder after annealing treatment is fully stirred with the functional prelithiation electrolyte, heated at 50-60 DEG C while stirring until the liquid is dried, and the powder produced after drying is ground to obtain regenerated natural graphite powder; The regenerated natural graphite powder is further dried, electrolyte is added dropwise, and coated to obtain a lithium ion battery natural graphite negative electrode sheet; After adding 5 ml of functional prelithiation electrolyte to the lithium ion battery natural graphite negative electrode sheet, the battery is assembled, and the functional prelithiation electrolyte is used to continuously supply lithium to the battery for subsequent use, and the electrochemical test performance of the battery is shown in Figure 1 and Figure 2 .​​ The prepared regenerated natural graphite electrode was assembled into a button-type half-cell for electrochemical test: the first coulombic efficiency (ICE) of the regenerated natural graphite negative electrode assembled half-cell reached 100.09%, and had good cycle stability, with a capacity retention rate of 99.08%, and the constant current intermittent titration technique (GITT) test found that it exhibited good Li + diffusion coefficient, the Li + diffusion coefficient of the regenerated natural graphite electrode in the discharge / charge stage Figure 3 and Figure 4 as shown in the figure.

[0037] Embodiment 2: A waste lithium-ion battery graphite negative electrode regeneration method provided in the embodiment has the following steps: The waste artificial graphite pole piece is subjected to ultrasonic stripping treatment to obtain waste artificial graphite powder, and the waste artificial graphite powder is subjected to high-temperature annealing treatment, the temperature is increased to 800 DEG C at a rate of 5 DEG C / min, and maintained at 1000 DEG C for 2 hours; The functional group-containing pre-lithiation reagent is prepared by dissolving lithium metal and 2-aminobiphenyl in 2-methyltetrahydrofuran solvent and stirring to obtain a functional group-containing pre-lithiation reagent with a concentration of 0.7 mol / L; Preparation of functional pre-lithiation electrolyte: in an argon environment, ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 55:45, then 1.5 mol / L Merck lithium hexafluorophosphate solution is added to the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; the pre-lithiation reagent containing 2-aminobiphenyl is fully mixed with the electrolyte to obtain a functional pre-lithiation electrolyte, and the volume ratio of the functional group-containing pre-lithiation reagent to the electrolyte is 1:4; The artificial graphite powder after annealing treatment is fully stirred with the functional pre-lithiation electrolyte, heated to 50-60 DEG C while stirring until the liquid is dried, and the powder after drying is ground to obtain regenerated artificial graphite powder; The regenerated artificial graphite powder is further dried and treated, and the electrolyte is added dropwise to obtain a lithium-ion battery artificial graphite negative pole piece; The lithium-ion battery artificial graphite negative pole piece is assembled into a battery after adding 5 ml of functional pre-lithiation electrolyte, and the functional pre-lithiation electrolyte is used to continuously supply lithium for the battery, and the electrochemical test performance of the battery is as shown in Figure 5 and Figure 6 ; The prepared regenerated artificial graphite electrode of the embodiment was assembled into a button-type half cell for electrochemical test: the first coulomb efficiency (ICE) of the regenerated artificial graphite negative electrode assembled into a half cell reached 100.09%, and had good cycle stability, with a capacity retention rate of 99.2%, and the constant current intermittent titration technique (GITT) test found that it exhibited good Li + diffusion coefficient in the discharge / charge stage of the regenerated natural graphite electrode. + The Li Figure 7 diffusion coefficient diagram is shown in Figure 8 and .

[0038] Embodiment 3: A waste lithium-ion battery graphite negative electrode regeneration method provided by the embodiment has the following steps: The waste nanometer graphite pole piece is subjected to ultrasonic stripping treatment to obtain waste nanometer graphite powder, and the waste nanometer graphite powder is subjected to high-temperature annealing treatment, the temperature is increased to 1000℃ at a rate of 5℃ / min, and maintained at 1500℃ for 2 hours. The pre-lithiation reagent containing a functional group is configured, lithium metal and 9-cyano anthracene are dissolved in 2-methyl tetrahydrofuran solvent to obtain a pre-lithiation reagent containing a functional group, and the concentration is 1.2 mol / L. Preparation of functional pre-lithiation electrolyte: in an argon environment, ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 55:45, then 1.5 mol / L Merck lithium hexafluorophosphate solution is added to the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; the pre-lithiation reagent containing 9-cyano anthracene is fully mixed with the electrolyte to obtain a functional pre-lithiation electrolyte, and the volume ratio of the pre-lithiation reagent containing a functional group to the electrolyte is 1:4. The nanometer graphite powder after annealing treatment is fully stirred with the functional pre-lithiation electrolyte, heated at 50-60℃ while stirring until the liquid is dried, and the powder produced after drying is ground to obtain regenerated nanometer graphite powder; The regenerated nanometer graphite powder is further dried and treated, electrolyte is added dropwise, and a lithium-ion battery nanometer graphite negative pole piece is coated; After 5ml of functional pre-lithiation electrolyte is added dropwise on the lithium-ion battery nanometer graphite negative pole piece, the battery is assembled, the functional pre-lithiation electrolyte is used to continuously supply lithium for the battery, and the electrochemical test performance of the battery is shown in Figure 9 and Figure 10 . The prepared regenerated nanometer graphite electrode of the embodiment was assembled into a button-type half cell for electrochemical test: the first coulomb efficiency (ICE) of the regenerated nanometer graphite negative electrode assembled into a half cell reached 102.04%, and had good cycle stability, with a capacity retention rate of 99.7%, and the constant current intermittent titration technique (GITT) test found that it exhibited good Li+ The Li+ diffusion coefficient graph of the discharge / charge stage of the regenerated natural graphite electrode is as shown in Figure 11 and Figure 12 ;

[0039] Embodiment 4 provides a method for regenerating a graphite negative electrode of a waste lithium ion battery, and the steps are as follows: The waste low-impurity graphite electrode sheet is subjected to ultrasonic stripping treatment to obtain waste low-impurity graphite powder, and the waste low-impurity graphite powder is subjected to high-temperature annealing treatment, the temperature is increased to 1200℃ at a rate of 5℃ / min, and the temperature is kept at 1200℃ for 2 hours; The pre-lithiation reagent containing functional groups is configured, lithium metal and 2,3-dicyanonaphthalene are dissolved in 2-methyltetrahydrofuran solvent to obtain a pre-lithiation reagent containing functional groups, and the concentration is 1.6 mol / L; The functional pre-lithiation electrolyte is prepared: in an argon environment, ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 55:45, then 1.5 mol / L Merck lithium hexafluorophosphate solution is added to the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; the pre-lithiation reagent containing 2,3-dicyanonaphthalene is fully mixed with the electrolyte to obtain a functional pre-lithiation electrolyte, and the volume ratio of the pre-lithiation reagent containing functional groups to the electrolyte is 1:4; The low-impurity graphite powder after annealing treatment is fully stirred with the functional pre-lithiation electrolyte, heated to 50-60℃ while stirring until the liquid is dried, and the powder after drying is ground to obtain regenerated low-impurity graphite powder; The regenerated low-impurity graphite powder is further dried and treated, electrolyte is added dropwise, and the low-impurity graphite negative electrode sheet of the lithium ion battery is coated; After 5ml of functional pre-lithiation electrolyte is added dropwise on the low-impurity graphite negative electrode sheet of the lithium ion battery, the battery is assembled, the functional pre-lithiation electrolyte is used to continuously supply lithium for the battery, and the electrochemical test performance of the battery is as shown in Figure 13 and Figure 14 ; The regenerated low-impurity graphite electrode prepared in this embodiment is assembled into a button-type half-cell, and the electrochemical test is performed: the first coulombic efficiency (ICE) of the half-cell assembled with the regenerated low-impurity graphite negative electrode reaches 112.27%, and has good cycle stability, the capacity retention rate is 99.78%, and the constant current intermittent titration technique (GITT) test finds that it has good Li + The Li+ diffusion coefficient graph of the discharge / charge stage of the regenerated natural graphite electrode is as shown in Figure 15 and Figure 16 .

[0040] Embodiment 5 provides a waste lithium ion battery graphite negative electrode regeneration method, the steps are as follows: The waste expanded graphite pole piece is subjected to ultrasonic stripping treatment to obtain waste low-impurity graphite powder, and the waste expanded graphite powder is subjected to high-temperature annealing treatment, the temperature is increased to 1500 DEG C at a rate of 5 DEG C / min, and maintained at 1500 DEG C for 2 hours; The prelithiation reagent containing functional groups is configured, lithium metal and 2,2'-diaminobiphenyl are dissolved in 2-methyltetrahydrofuran solvent to obtain the prelithiation reagent containing functional groups, and the concentration is 2 mol / L; The functional prelithiation electrolyte is prepared: in an argon environment, ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 55:45, then 1.5 mol / L Merck lithium hexafluorophosphate solution is added to the mixed solution of ethylene carbonate and diethyl carbonate to form an electrolyte; the prelithiation reagent containing 2,2'-diaminobiphenyl is fully mixed with the electrolyte to obtain the functional prelithiation electrolyte, and the volume ratio of the prelithiation reagent containing functional groups to the electrolyte is 1:4; The expanded graphite powder subjected to the annealing treatment is fully stirred with the functional prelithiation electrolyte, heated at 50-60 DEG C until the liquid is dried, and the powder produced after drying is ground to obtain regenerated expanded graphite powder; The regenerated expanded graphite powder is further dried, electrolyte is added dropwise, and coating is performed to obtain a lithium ion battery expanded graphite negative pole piece; After 5 ml of the functional prelithiation electrolyte is added dropwise on the lithium ion battery expanded graphite negative pole piece, a battery is assembled, the functional prelithiation electrolyte is used to continuously supply lithium for the battery, and the electrochemical test performance of the battery is as shown in Figure 17 and Figure 18 . The regenerated expanded graphite electrode prepared in this embodiment is assembled into a button-type half battery, and electrochemical test is performed: the first coulombic efficiency (ICE) of the half battery assembled with the regenerated expanded graphite negative electrode reaches 121.09%, and has good cycle stability, the capacity retention rate is 99.32%, and the lithium ion battery is found to have good Li + diffusion coefficient through the galvanostatic intermittent titration technique (GITT) test, and the Li+ diffusion coefficient diagram of the regenerated natural graphite electrode in the discharge / charge stage is as shown in Figure 19 and Figure 20 .

[0041] The above is only a preferred embodiment of the present application, and is not intended to limit the present application, any slight modification, equivalent replacement and improvement made according to the technical essence of the present application to the above embodiment shall be included in the protection scope of the technical solution of the present application.

Claims

1. A method for regenerating graphite anodes from waste lithium-ion batteries, characterized in that, The steps are as follows: S1. Waste graphite electrode sheets are subjected to ultrasonic peeling to obtain waste graphite powder. The waste graphite powder is then subjected to high-temperature annealing, which involves slow heating and constant temperature maintenance. S2. Lithium metal and anionic ligands containing functional groups are added to 2-methyltetrahydrofuran solvent and dissolved completely by stirring to obtain a pre-lithiation reagent containing functional groups. S3. The graphite powder that has undergone high-temperature annealing is stirred evenly with a pre-lithiation reagent containing functional groups, and then heated while stirring at 50-60℃ until dry. The dried product is then ground to obtain regenerated graphite powder that compensates for the loss of active lithium caused by the supplementary discharge.

2. The method for regenerating graphite anodes from waste lithium-ion batteries according to claim 1, characterized in that, The waste graphite electrode sheets include: waste natural graphite electrode sheets, waste artificial graphite electrode sheets, waste block graphite electrode sheets, waste flake graphite electrode sheets, waste sandstone graphite electrode sheets, waste electrode graphite electrode sheets, waste spherical graphite electrode sheets, waste expanded graphite electrode sheets, waste nano graphite electrode sheets, and waste low-impurity graphite electrode sheets.

3. The method for regenerating graphite anodes from waste lithium-ion batteries according to claim 1, characterized in that, During the high-temperature annealing process of waste graphite powder: the maximum annealing temperature is 600-1500℃, the slow heating rate is 5℃ / min, and the temperature is kept constant at the corresponding maximum temperature for 2 hours.

4. The method for regenerating graphite anodes from waste lithium-ion batteries according to claim 1, characterized in that, Anionic ligands containing functional groups include one or more of the following: 4-cyanobiphenyl, 1,4-dicyanonaphthalene, 2,7-dicyanonaphthalene, 2,3-dicyanonaphthalene, 1-amino-2-cyanonaphthalene, 9-cyanoanthracene, 9,10-dicyanoanthracene, 2-methoxybiphenyl, 3-methoxybiphenyl, 4-methoxybiphenyl, 4,4-dimethoxybiphenyl, 3,3'-dimethoxybiphenylamine, 3-amino-4-methoxybiphenyl, 1-methoxynaphthalene, 2-methoxynaphthalene, 4,4'-dimethoxyoctafluorobiphenyl, 4,4'-diaminooctafluorobiphenyl, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2,2'-diaminobiphenyl, 1,4-diaminonaphthalene, 2,3-diaminonaphthalene, 1,8-diaminonaphthalene, 1,5-diaminonaphthalene, 2,7-diaminonaphthalene, and 1,2-diaminonaphthalene.

5. The method for regenerating graphite anodes from waste lithium-ion batteries according to claim 1, characterized in that, The molar ratio of lithium metal to the functional anionic ligand in the 2-methyltetrahydrofuran solvent is 1:

1. The concentration of the pre-lithiation reagent containing the functional group is ensured to be between 0.2 mol / L and 2 mol / L. There is no specific ratio for lithium metal, the functional anionic ligand, and 2-methyltetrahydrofuran; it is sufficient to ensure that they are fully dissolved. To ensure the complete dissolution of lithium metal and anionic ligands containing functional groups in 2-methyltetrahydrofuran solvent, continuous stirring for 1 hour is required: for the first 30 minutes, stirring at 40°C and 850 rpm to dissolve the thin sheet-like lithium metal into fine fragments; for the next 30 minutes, stirring at 450 rpm without heating is required to better dissolve the lithium metal.

6. The method for regenerating graphite anodes from waste lithium-ion batteries according to claim 1, characterized in that, The graphite powder that has undergone high-temperature annealing is mixed with a pre-lithiation reagent containing functional groups at a mass ratio of 4:3 and stirred evenly.

7. A lithium-ion battery graphite anode sheet prepared using the method for regenerating waste lithium-ion battery graphite anodes according to any one of claims 1-6, characterized in that: The recycled graphite powder is further dried, electrolyte is added, and it is coated to obtain a graphite anode sheet for lithium-ion batteries.

8. An application of the graphite negative electrode sheet for a lithium-ion battery as described in claim 7, characterized in that, The steps are as follows: A. Preparation of functional pre-lithiation electrolyte: In an argon atmosphere, ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 55:

45. Then, 1.5 mol / L Merck lithium hexafluorophosphate solution is added to the ethylene carbonate and diethyl carbonate mixture to form an electrolyte. The pre-lithiation reagent containing functional groups is thoroughly mixed with the electrolyte to obtain the functional pre-lithiation electrolyte, with a volume ratio of 1:4 between the pre-lithiation reagent containing functional groups and the electrolyte. B. After adding 5 ml of functional pre-lithiated electrolyte to the graphite anode sheet of a lithium-ion battery, the battery is assembled. The functional pre-lithiated electrolyte is used to continuously supply lithium to the battery. The pressure of the tablet press used for battery assembly is 350-750 kg / cm². 2 .

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