A method for normalizing the performance of negative electrode graphite in multi-source retired lithium-ion batteries

Abstract

The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries. The regeneration method comprises mixing negative electrode graphite raw materials of multi-source retired lithium-ion batteries in a certain proportion to obtain multi-source mixed failed graphite raw materials; adding the obtained multi-source mixed failed graphite raw materials to a graphite device, and then performing flash discharge treatment to obtain regenerated graphite. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries of the present invention has strong adaptability to raw materials, and can repair common types of retired negative electrode graphite materials on the market. The regeneration method of the present invention realizes the re-graphitization of retired negative electrode graphite through the technology of flash discharge, has a short process flow, is economical and environmentally friendly, requires simple equipment, and has extremely low cost, and has strong application value and significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for normalizing the performance of negative electrode graphite in retired lithium-ion batteries from multiple sources. Background Art

[0002] Existing recycling methods, such as high-temperature pyrometallurgy and hydrometallurgy, primarily focus on recovering valuable metals from retired cathode materials, while neglecting retired anode graphite. In pyrometallurgy, graphite is incinerated on-site as a reducing agent to reduce the valence of transition metals, thereby stabilizing the low-valence metal elements in solution. In traditional hydrometallurgical methods, waste graphite is often retained in the leaching residue. Furthermore, with advances in disassembly technology, the purity of retired battery materials has significantly improved. As a major future development direction, the regeneration and repair of anode graphite from retired battery materials deserves attention. Finally, with the large-scale production of lithium-ion batteries, more and more scraps are generated during non-standard production processes. The recycling of this graphite also deserves attention.

[0003] Given the differences in sources, production processes, and separation methods, the reuse of waste graphite faces great challenges, which makes it difficult to achieve a unified regeneration process. The failure mechanism of graphite negative electrode materials involves the failure of the solid electrolyte membrane (SEI), lithium dendrite growth, destruction of graphite interlayer spacing caused by solvent intercalation, and particle cracking. Although the traditional pickling process can effectively remove organic lithium-containing impurities on the surface, it will also cause varying degrees of damage to the graphite crystal structure; although the high-temperature roasting process can achieve graphitization and reconstruction of damaged graphite structures, the high cost caused by large amounts of energy consumption and the stringent requirements for equipment limit its further application; carbon coating technology can enhance the surface properties of graphite, but there are still challenges such as excessively long processes, precise control requirements, and high costs.

[0004] Therefore, the existing technology for repairing retired negative electrode graphite is not only difficult to handle a variety of waste graphite, but also has disadvantages such as poor repair effect, high repair cost, and complex repair process. It is urgent to develop a new economical recovery process for retired negative electrode graphite to achieve normalized repair and regeneration of retired graphite. Summary of the Invention

[0005] The present invention provides a method for normalizing the performance of negative electrode graphite of retired lithium-ion batteries from multiple sources, which is used to solve the problems that the existing retired negative electrode graphite repair technology is not only difficult to process a variety of waste graphites, but also has poor repair effects, high repair costs, and a complicated repair process.

[0006] According to a first aspect of the present invention, the present invention provides a method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries, comprising the following steps:

[0007] Step 1: Mixing multiple sources of retired lithium-ion battery negative electrode graphite raw materials in a certain proportion to obtain multi-source mixed failed graphite raw materials;

[0008] Step 2: adding the multi-source mixed spent graphite raw material obtained in step 1 into a graphite device, and then performing flash discharge treatment to obtain regenerated graphite.

[0009] In the above scheme, the present invention's method for regenerating the performance of multi-source retired lithium-ion battery negative electrode graphite to normalize its performance is achieved by using Joule heat generated by flash discharge to effectively act on the damaged graphite structure in a short period of time, while simultaneously removing surface impurities and achieving normalized performance repair of the multi-source graphite. The regeneration method of the present invention has strong adaptability to raw materials and can repair different types of retired negative electrode graphite materials on the market. It can simultaneously process multiple types of waste graphite with good repair effects, requires simple equipment, has extremely low costs, and a simple repair process, thus having strong application value.

[0010] The retired lithium-ion battery negative electrode graphite material in the present invention refers to the main component of the negative electrode material of the used lithium-ion battery, the failed graphite negative electrode material caused by factors such as failure of the solid electrolyte membrane, lithium dendrite growth, destruction of graphite interlayer spacing caused by solvent intercalation, and particle cracking during use, as well as one or more of the scraps of negative electrode graphite material caused by non-standard cutting process and injection process during production.

[0011] Furthermore, the multi-source retired lithium-ion battery negative electrode graphite raw materials include multiple types of graphite scraps generated in the production process of negative electrode materials, negative electrode graphite materials obtained by disassembling retired power batteries, and leached slag obtained by hydrometallurgy of crushed black powder of retired power batteries.

[0012] Preferably, in the multi-source retired lithium-ion battery negative electrode graphite raw materials, the weight ratio of graphite scraps generated in the negative electrode material production process, the negative electrode graphite material obtained by disassembling retired power batteries, and the leaching residue obtained by hydrometallurgy of crushed black powder of retired power batteries is (1-5): (1-2): (1-3).

[0013] Optionally, the weight ratio of the graphite scraps generated during the production of the negative electrode material, the negative electrode graphite material obtained from the disassembly of retired power batteries, and the leached residue obtained from the hydrometallurgical process of crushed black powder from retired power batteries can be 1:1:1, 2:1:1, 3:1:1, 4:1:1, 5:1:1, 1:1:2, 1:1:3, 2:1:2, 2:1:3, 1:2:1, 1:2:2, 1:2:3, or 5:2:2, etc., and of course, it is not limited to these ratios. The regeneration difficulty of the leached residue obtained from the hydrometallurgical process of crushed black powder from retired power batteries is higher than that of the graphite scraps generated during the production of the negative electrode material and the negative electrode graphite material obtained from the disassembly of retired power batteries. In order to achieve better regeneration effects, it is preferred that the leached residue obtained from the hydrometallurgical process of crushed black powder from retired power batteries accounts for less than 50% by weight of the negative electrode graphite raw materials of multi-source retired lithium-ion batteries, and preferably less than or equal to 35%. In some specific embodiments, the leached slag obtained by hydrometallurgy of crushed black powder of retired power batteries accounts for 30-35% by weight of the negative electrode graphite raw materials of multi-source retired lithium-ion batteries, which can achieve a better regeneration effect.

[0014] Furthermore, in the step 2, the flash discharge treatment is to place the graphite device containing multi-source mixed spent graphite raw materials in a flash discharge device, raise the temperature to the reaction temperature at a certain heating rate, keep the temperature for a period of time and then cool it to obtain regenerated graphite.

[0015] Furthermore, the reaction temperature is 2800-3200° C., and the holding time is 0.1s-10s.

[0016] Alternatively, the reaction temperature may be 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3050°C, 3100°C, 3150°C, or 3200°C, and may also be other values ​​within the above range, without limitation. The holding time may be 0.1s, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, or 10s, and may also be other values ​​within the above range, without limitation. Preferably, it is 0.5s-5s, and more preferably 0.5s-1.5s. If the holding time is too long, serious damage to the equipment may occur.

[0017] In the above scheme, by limiting the reaction temperature and holding time within a reasonable range, it is beneficial to improve the graphitization efficiency of the raw material, thereby improving the product quality of the regenerated graphite.

[0018] Furthermore, the heating rate is 0.01°C / s to 3000°C / s, preferably 1°C / s to 3000°C / s.

[0019] Optionally, the heating rate can be 0.01℃ / s, 0.05℃ / s, 1℃ / s, 10℃ / s, 50℃ / s, 100℃ / s, 200℃ / s, 500℃ / s, 800℃ / s, 1000℃ / s, 1500℃ / s, 2000℃ / s, 2500℃ / s or 3000℃ / s, etc. Of course, it can also be other values ​​within the above range, which is not limited here, and is preferably 1℃ / s to 3000℃ / s.

[0020] In the above scheme, by limiting the heating rate within a reasonable range, the graphitization efficiency of the raw material can be improved, thereby improving the product quality of the regenerated graphite.

[0021] Furthermore, the discharge current of the flash discharge treatment is 5-15A, and the discharge voltage is 150-200V.

[0022] Optionally, the discharge current of the flash discharge treatment can be 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A, 14A or 15A, etc., and of course it can also be other values ​​within the above range, which is not limited here, preferably 8 to 12A, and the discharge voltage can be 150V, 160V, 170V, 180V, 190V or 200V, etc., and of course it can also be other values ​​within the above range, which is not limited here, preferably 170 to 190V.

[0023] In the above solution, the flash discharge efficiency can be improved by limiting the discharge current and discharge voltage of the flash discharge process to a reasonable range.

[0024] Furthermore, the cooling includes natural air drying cooling or cooling at a cooling rate of 0.01°C / s to 3000°C / s. Furthermore, natural air drying cooling is prone to structural collapse. In order to maintain the original structure after graphitization to a relatively large extent, cooling at a cooling rate of 0.01°C / s to 3000°C / s is preferred.

[0025] Optionally, the cooling rate can be 0.01℃ / s, 0.05℃ / s, 1℃ / s, 10℃ / s, 50℃ / s, 100℃ / s, 200℃ / s, 500℃ / s, 800℃ / s, 1000℃ / s, 1500℃ / s, 2000℃ / s, 2500℃ / s or 3000℃ / s, etc. Of course, it can also be other values ​​within the above range, which is not limited here, and is preferably 1℃ / s to 3000℃ / s.

[0026] Furthermore, the flash discharge treatment is performed in a specific gas atmosphere, wherein the specific gas includes one or more of nitrogen, argon, oxygen and air, preferably one or two of nitrogen and argon.

[0027] Furthermore, the graphite device is one or more of a graphite boat, a graphite tube and graphite carbon paper.

[0028] Furthermore, the flash discharge treatment in step 2 is performed to obtain a reaction product, and the obtained reaction product is washed and then vacuum dried to obtain regenerated graphite;

[0029] Preferably, the washing solution used in the washing is a mixture of one or more of hydrochloric acid, sulfuric acid, phosphoric acid and water; more preferably, the concentration of the washing solution is 0.01 mol / L to 8 mol / L.

[0030] Acid washing can remove some oxides produced during the graphitization process, ensuring the purity of the regenerated graphite. Optionally, the concentration of the washing solution can be 0.01 mol / L, 0.05 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L, and other values ​​within the above range are also possible and are not limited here.

[0031] Furthermore, in the step 1, multiple sources of retired lithium-ion battery negative electrode graphite raw materials are mixed in a certain proportion and then passed through a 50-200 mesh sieve to obtain a multi-source mixed failed graphite raw material.

[0032] In the above scheme, visible plastic impurities, collector debris, etc. are removed by screening to improve the quality of the regenerated graphite.

[0033] Furthermore, the regenerated graphite has a gram capacity of 300 mAh / g to 400 mAh / g at a current of 0.1 C and a specific surface area of ​​2 m 2 / g~20m 2 / g, pore volume 10m 3 / g~100m 3 / g.

[0034] The present invention provides a method for regenerating and normalizing the properties of decommissioned lithium-ion battery anode graphite from multiple sources. The method is highly adaptable to the raw materials used and can repair a wide variety of decommissioned anode graphite materials on the market. This method utilizes flash discharge technology to regraphitize decommissioned anode graphite. This method features a short process flow, is economical and environmentally friendly, requires simple equipment, and is extremely low-cost, offering significant application value and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a schematic diagram of the process flow of a method for normalizing the performance of negative electrode graphite in multi-source retired lithium-ion batteries according to Example 1 of the present invention.

[0037] Figure 2 This is a rate performance diagram of the recycled graphite (FG) obtained in Example 1 of the present invention and several other materials (graphite scraps SG, negative electrode graphite material DG obtained by disassembling retired power batteries, and graphite HG in hydrometallurgical leaching slag of crushed black powder from retired power batteries) under current conditions of 0.1C / 0.2C / 0.5C / 1C / 2C / 0.1C.

[0038] Figure 3 This is a graph of the first charge and discharge performance of the recycled graphite (FG) obtained in Example 1 of the present invention and several other materials (graphite scraps SG, negative electrode graphite material DG obtained by disassembling retired power batteries, and graphite HG in hydrometallurgical leaching slag of crushed black powder from retired power batteries) under 0.1C current conditions.

[0039] Figure 4 This is a cycle performance diagram of the recycled (FG) obtained in Example 1 of the present invention and several other materials (graphite scraps SG, negative electrode graphite material DG obtained by disassembling retired power batteries, and graphite HG in hydrometallurgical leaching residue of crushed black powder from retired power batteries) after 500 cycles under 1C current conditions. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] The beneficial effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0042] In the following examples, the graphite scraps generated during the production of the negative electrode materials, the negative electrode graphite materials obtained by disassembling retired power batteries, and the leaching residue obtained by hydrometallurgy of crushed black powder from retired power batteries were respectively sourced from Shenzhen Xinmao New Energy Technology Co., Ltd., China New Aviation Technology Group Co., Ltd. (CALB), and Zhejiang Huayou Cobalt Co., Ltd.

[0043] Example 1

[0044] This embodiment provides a method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries. The process flow diagram is as follows: Figure 1 As shown, it includes the following steps:

[0045] Step 1: Mix the graphite scraps generated in the production process of the negative electrode material, the negative electrode graphite material obtained by disassembling retired power batteries, and the leaching residue obtained by hydrometallurgy of crushed black powder of retired power batteries in a ratio of 1:1:1, and sieve them through a 200-mesh sieve. The sieved material obtained is used as the multi-source mixed spent graphite raw material.

[0046] Step 2: Take 1g of the multi-source mixed spent graphite raw material obtained in step 1 and add it to a graphite tube. Place it in a flash discharge equipment heating furnace under nitrogen protection (the flash discharge equipment discharge current is 10A and the discharge voltage is 180V). Heat it to 3000℃ at a heating rate of 3000℃ / s. After holding it for 1s, cool it to room temperature at a cooling rate of 1000℃ / s and take it out. First wash it with 0.1M dilute hydrochloric acid, then wash it with deionized water until the washing liquid is neutral, and then dry it at 25℃ and -0.085MPa vacuum to obtain regenerated graphite.

[0047] Example 2

[0048] This embodiment provides a method for normalizing the performance of negative electrode graphite of retired lithium-ion batteries from multiple sources. The method differs from Example 1 in that in step 1, graphite scraps generated during the production of negative electrode materials, negative electrode graphite materials obtained by disassembling retired power batteries, and leaching residue obtained by hydrometallurgy of crushed black powder from retired power batteries are mixed in a ratio of 2:1:3.

[0049] Example 3

[0050] This embodiment provides a method for normalizing the performance of negative electrode graphite of retired lithium-ion batteries from multiple sources. The method differs from Example 1 in that in step 1, graphite scraps generated during the production of negative electrode materials, negative electrode graphite materials obtained by disassembling retired power batteries, and leaching residue obtained by hydrometallurgy of crushed black powder from retired power batteries are mixed in a ratio of 5:2:2.

[0051] Example 4

[0052] This embodiment provides a method for normalizing the performance of negative electrode graphite in retired lithium-ion batteries from multiple sources. The difference from Example 1 is that the holding time in step 2 is 5 seconds.

[0053] Example 5

[0054] This embodiment provides a method for normalizing the performance of negative electrode graphite in retired lithium-ion batteries from multiple sources. The difference from Example 1 is that the holding time in step 2 is 10 seconds.

[0055] Example 6

[0056] This embodiment provides a method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries. The difference from Example 1 is that the cooling in step 2 is natural air drying cooling.

[0057] Example 7

[0058] This embodiment provides a method for normalizing the performance of negative electrode graphite of retired lithium-ion batteries from multiple sources. The difference from Example 1 is that argon is used instead of nitrogen in the gas atmosphere for the flash discharge treatment in step 2.

[0059] Example 8

[0060] This embodiment provides a method for normalizing the performance of negative electrode graphite in retired lithium-ion batteries from multiple sources. The method differs from Embodiment 1 in that the gas atmosphere for the flash discharge treatment in Step 2 is replaced by air instead of nitrogen.

[0061] Example 9

[0062] This embodiment provides a method for normalizing the performance of negative electrode graphite of retired lithium-ion batteries from multiple sources. The difference from Example 1 is that in step 1, the negative electrode graphite is screened through a 50-mesh sieve.

[0063] Comparative Example 1

[0064] This comparative example provides a method for regenerating graphite from the negative electrodes of retired lithium-ion batteries from multiple sources. This method differs from Example 1 in that, in step 2, a different method is used to treat the mixed spent graphite raw material from multiple sources. Specifically, the method utilizes the microwave absorption properties of carbon materials and treats the graphite using microwave heating. The microwave heating is performed at 800W for 5 seconds.

[0065] Comparative Example 2

[0066] This comparative example provides a method for regenerating negative electrode graphite of multi-source retired lithium-ion batteries, which differs from Example 1 in that: in step 2, other methods are used to perform high-temperature sulfuric acid roasting on the hydrometallurgical leaching residue of the crushed black powder of retired power batteries. The specific treatment method is to add sulfuric acid during the roasting process for acidification treatment to achieve the removal of impurities and the reconstruction of graphite structural materials.

[0067] Comparative Example 3

[0068] This embodiment provides a method for normalizing the performance of negative electrode graphite in retired lithium-ion batteries from multiple sources. The method differs from Example 1 in that a tubular furnace is used for heating in step 2. The method is performed under nitrogen protection, with the temperature raised to 1300°C at a rate of 5°C / min, maintained for 5 hours, and then cooled naturally.

[0069] Test example

[0070] The specific surface area and pore size distribution of the regenerated graphite obtained in the embodiment and the comparative example were tested using nitrogen adsorption and desorption isotherms and pore size distribution curves, respectively. The assembled battery was placed in a constant temperature box at 25°C for 12 hours and connected to a blue electric test system. The test was performed according to the procedure, and the charge and discharge curve interval was set to 2.0-0.0005V. Constant current charge and discharge were performed at different current rates.

[0071] The test results are shown in Table 1 below.

[0072] Table 1. Comparison of structural properties and electrochemical properties of different recycled graphites

[0073]

[0074]

[0075] It can be seen from the experimental data in Table 1 that the normalized regeneration method for the performance of negative electrode graphite of multi-source retired lithium-ion batteries of the present invention can recycle and treat multi-source negative electrode graphite, and can achieve a good repair effect in a short time of heat preservation. The performance of the regenerated graphite (FG) obtained in Example 1 is compared with that of the initial raw material graphite scrap SG, the negative electrode graphite material DG obtained by disassembling retired power batteries, and the graphite HG in the hydrometallurgical leaching residue of crushed black powder of retired power batteries. Figure 2-4 As shown, the regenerated graphite (FG) obtained by the method of the present invention has significantly improved rate performance, initial charge and discharge performance, and cycle performance under 0.1C current conditions. The obtained regenerated graphite has a gram capacity of greater than 330 mAh / g under 0.1C current conditions, and the capacity is retained at least 90% after 100 cycles at 1C current. The regenerated graphite obtained under the conditions of Examples 1, 4, 5, 7, and 8 has a gram capacity of greater than 345 mAh / g under 0.1C current conditions, and the capacity is retained at least 99% after 500 cycles at 1C current.

[0076] It can be seen from the results of Example 1 and Comparative Examples 2-3 that, compared with the repair methods of microwave treatment and high-temperature sulfuric acid roasting, the method of the present invention can significantly improve the repair effect and improve the efficiency, thereby achieving rapid repair of retired negative electrode graphite materials. It can be seen from the results of Example 1 and Comparative Example 3 that, compared with traditional tubular furnace heating, the present invention adopts flash discharge heating, which has a higher energy utilization effect. The traditional tubular furnace heating energy utilization rate is extremely low, and the surface organic matter (such as PVDF binder) and residual SEI can be gradually removed as the temperature rises. However, the deep-seated graphite damaged structure is poorly repaired due to insufficient energy concentration.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries, characterized in that: The steps include: Step 1: Mixing multiple sources of retired lithium-ion battery negative electrode graphite raw materials in a certain proportion to obtain a multi-source mixed failed graphite raw material; in the multi-source retired lithium-ion battery negative electrode graphite raw materials, the weight ratio of graphite scraps generated in the negative electrode material production process, the negative electrode graphite material obtained by disassembling retired power batteries, and the leaching residue obtained by hydrometallurgy of crushed black powder of retired power batteries is (1-5): (1-2): (1-3); Step 2: adding the multi-source mixed spent graphite raw material obtained in step 1 into a graphite device, and then performing a flash discharge treatment, wherein the discharge current of the flash discharge treatment is 5 to 15A and the discharge voltage is 150 to 200V to obtain regenerated graphite; In the step 2, the flash discharge treatment is to place a graphite device containing multi-source mixed failed graphite raw materials in a flash discharge device, raise the temperature to the reaction temperature at a heating rate of 0.01°C / s to 3000°C / s, keep the temperature for a period of time and then cool to obtain regenerated graphite; the reaction temperature is 2800 to 3200°C, and the holding time is 0.1s to 10s.

2. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: The heating rate is 1°C / s to 3000°C / s; and / or the cooling includes natural air drying cooling or cooling at a cooling rate of 0.01°C / s to 3000°C / s.

3. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 2, characterized in that: The cooling is performed at a temperature drop rate of 1°C / s to 3000°C / s.

4. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: The flash discharge treatment is performed in a specific gas atmosphere, wherein the specific gas includes one or more of nitrogen, argon, oxygen and air.

5. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 4, characterized in that: The specific gas is one or both of nitrogen and argon.

6. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: The graphite device is one or more of a graphite boat, a graphite tube and graphite carbon paper.

7. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: In step 2, a flash discharge treatment is performed to obtain a reaction product, and the obtained reaction product is washed and then vacuum dried to obtain regenerated graphite.

8. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 7, characterized in that: The washing solution used in the washing is a mixture of one or more of hydrochloric acid, sulfuric acid, phosphoric acid and water.

9. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 8, characterized in that: The concentration of the washing solution is 0.01 mol / L to 8 mol / L.

10. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: In the step 1, multiple sources of retired lithium-ion battery negative electrode graphite raw materials are mixed in a certain proportion and then passed through a 50-200 mesh sieve to obtain a multiple source mixed spent graphite raw material.

11. The method for normalizing the performance of negative electrode graphite of multi-source retired lithium-ion batteries according to claim 1, characterized in that: The regenerated graphite has a gram capacity of 300 mAh / g to 400 mAh / g at a current of 0.1 C and a specific surface area of ​​2 m 2 / g~20m 2 / g, pore volume 10m 3 / g~100m 3 / g.

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