A method for recovering graphite material from tailings of waste power batteries

Abstract

The application belongs to the technical field of recycling graphite materials, and particularly relates to a method for recycling graphite materials from tailings of waste power batteries. The method comprises the following steps: adding the battery tailings into a culture solution containing a composite functional flora, and fermenting for 5-8 days to obtain fermented tailings; carrying out microwave irradiation treatment on the fermented tailings under nitrogen protection to obtain heat-treated tailings; crushing the heat-treated tailings, and then carrying out flotation separation to obtain graphite slurry; carrying out spray drying on the graphite slurry to obtain graphite powder; mixing the graphite powder with a biomass carbon precursor, and then carrying out microwave heating treatment to obtain regenerated graphite. The method is simple in process, low in energy consumption, and friendly to the environment, and the regenerated graphite obtained by the method is high in purity and excellent in electrochemical performance, and can be directly used for the production of negative electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of graphite material recycling technology, specifically relating to a method for recycling graphite materials from waste power battery tailings. Background Technology

[0002] With the development of technology, the installed capacity of lithium iron phosphate batteries has been increasing year by year, and the scale of retired power batteries has also been growing annually. If not properly handled, this will lead to serious environmental and safety problems. Retired lithium iron phosphate batteries are rich in resources such as lithium, phosphorus, iron, and graphite, with content far exceeding that of primary mineral resources, making them a high-quality urban mineral resource. Recycling them can not only alleviate the environmental pressure caused by battery waste but also bring significant socio-economic benefits, contributing to the green and sustainable development of the entire industry. Lithium iron phosphate power batteries are mainly composed of a casing, positive electrode material, negative electrode material, and separator. Whether lithium iron phosphate battery materials are used safely and efficiently mainly depends on whether the metal materials of the positive electrode material can be used efficiently. Currently, most battery recycling companies only consider the utilization of the high-value lithium metal in the positive electrode material, without addressing the effective utilization of the iron phosphate slag. The remaining over 95% of the other components are treated as solid waste in the form of tailings.

[0003] Graphite is a common non-metallic mineral material with excellent properties such as high temperature resistance, high chemical stability, and thermal conductivity. However, its graphitization process requires a huge amount of energy. Graphite in the negative electrode material of lithium iron phosphate power batteries is a valuable resource, and its recycling can effectively alleviate graphite resource shortages and the high energy consumption problem in its production. Currently, the main methods for recycling graphite from waste power batteries are divided into five types: physical recycling, wet leaching recycling, thermal treatment recycling, and extraction. Physical recycling typically combines mechanical crushing, vibrating screening, and airflow separation processes to separate waste graphite based on the density properties of the negative electrode material. However, this method yields graphite with low added value and limited economic benefits. Wet leaching mainly uses solvents such as trifluoroacetic acid, hydrochloric acid, and sulfuric acid to leach and dissolve impurities in the negative electrode graphite, achieving graphite purification. This requires the use of concentrated acid, generating large amounts of acidic wastewater, which can pollute the environment if not properly treated. Thermal treatment recycling processes primarily remove impurities such as binders and conductive agents from waste graphite through high-temperature treatment. This process has wide applicability and high processing capacity, but it is energy-intensive and requires proper tail gas treatment. Extraction purification, using subcritical carbon dioxide and acetonitrile to extract graphite, can better protect the internal crystallinity of graphite and ensure good electrochemical performance; however, this method is complex and has high production costs. The above recycling methods suffer from high energy consumption, complex processes, low efficiency, and severe pollution. Furthermore, recycled graphite often has low first-efficiency, making it difficult to directly use in the manufacture of high-end batteries. Therefore, developing a simple, environmentally friendly, and low-cost recycling method is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for recovering graphite materials from waste power battery tailings. This recovery method is relatively simple, requires no high-temperature heating treatment, has low energy consumption, does not require concentrated acid treatment, is environmentally friendly, and yields high-purity recycled graphite with excellent electrochemical performance, which can be directly used in the production of anode materials.

[0005] The purpose of this invention is to provide a method for recovering graphite materials from waste power battery tailings, the method comprising the following steps:

[0006] (1) Add the battery tail residue to the culture medium containing composite functional bacteria, mix evenly, introduce air, ferment for 2-4 days, stop introducing air, continue fermentation for 3-4 days, and separate the fermented tail residue; specifically, the battery tail residue is the graphite residue after the recycled lithium iron phosphate battery material is crushed and separated, and its main impurities include organic matter such as binders, phosphates, iron oxides, oxides such as nickel, cobalt and manganese, copper, aluminum, lithium, etc.

[0007] (2) The fermentation tailings obtained in step (1) are subjected to microwave irradiation under nitrogen protection to obtain heat-treated tailings;

[0008] (3) After crushing the heat-treated tailings obtained in step (2), add water, inhibitor, collector and frother, mix evenly in a stirring tank and then enter the flotation column for flotation separation to obtain graphite slurry.

[0009] (4) The graphite slurry obtained in step (3) is spray-dried to obtain graphite powder;

[0010] (5) The graphite powder obtained in step (4) is mixed with the biomass carbon precursor, microwave heating is performed under nitrogen protection, and then cooled to obtain recycled graphite.

[0011] This invention combines "bio-fermentation + microwave activation + flotation + microwave remediation." First, a pre-removal treatment using composite microorganisms is employed. Organic acids (such as citric acid and oxalic acid) produced by the metabolism of these microorganisms selectively dissolve and remove metallic impurities such as cobalt, nickel, manganese, and lithium from the graphite surface and interlayers. Simultaneously, the microorganisms have a certain biodegradation effect on organic binders, achieving preliminary removal of impurities under mild conditions without the need for strong acid treatment, making it more environmentally friendly. Then, microwave heating is used. Utilizing the instantaneous heating characteristic of microwaves, residual organic binders and other organic matter are further vaporized and decomposed, rapidly escaping from the graphite layers. Simultaneously, inorganic impurities are dissociated into smaller particles. This method facilitates subsequent removal, eliminates the need for ultra-high temperature treatment, and has low energy consumption. Utilizing graphite's excellent natural floatability, a flotation process further separates residual inorganic impurities from the graphite, further improving graphite purity. The flotation-enriched graphite is then spray-dried to re-aggregate, followed by microwave treatment to decompose trace collectors and frothers introduced during flotation, promoting graphite structural rearrangement, repairing lattice defects, and forming an amorphous carbon coating layer on the graphite surface. The resulting regenerated graphite has high purity and a relatively dense structure, making it highly efficient as a battery anode material. This recycling process organically combines biological, physical, and chemical processes, making it rational, economical, environmentally friendly, and energy-efficient.

[0012] Preferably, in step (1) of the above technical solution, the composite functional bacterial group is a mixture of *Thiobacillus ferrooxidans*, *Leymus sulfideus* and *Aspergillus niger* in a volume ratio of 1.5-2.5:1:1, and the inoculation amount is 5-8% of the total amount of culture medium; the solid-liquid ratio of the battery tail residue to the culture medium is 1:5-8. This invention utilizes a composite functional microbial community of commonly used *Acidobacterium ferrooxidans*, *Leymus sulfideus*, and *Aspergillus niger*. Leveraging the metabolic activity and growth differences of *Acidobacterium ferrooxidans*, *Leymus sulfideus*, and acidophilic bacteria, sulfur in the culture medium is oxidized to sulfuric acid, and ferrous ions are oxidized to ferric ions. This efficiently dissolves metallic impurities such as cobalt, nickel, manganese, and lithium in battery residue. Furthermore, the invention utilizes the characteristic of *Aspergillus niger* fungi to produce organic acids such as citric acid and oxalic acid, which can form stable water-soluble complexes with metal ions, promoting the dissolution and separation of metals and preventing their redeposition on the graphite surface. Simultaneously, it can degrade certain organic binders, achieving preliminary impurity removal under mild conditions without damaging the graphite skeleton. This replaces the existing technology that uses external strong acid treatment, which not only consumes large amounts of chemicals but also results in difficult subsequent wastewater treatment.

[0013] Preferably, in the above technical solution, the components of the culture medium include ammonium sulfate 2-4 g / L, potassium dihydrogen phosphate 0.3-0.5 g / L, magnesium sulfate 0.4-0.7 g / L, potassium chloride 0.1-0.2 g / L, calcium chloride 0.02-0.05 g / L, sodium thiosulfate 5-10 g / L, ferrous sulfate 10-30 g / L, sucrose 8-20 g / L, and the balance being distilled water; the air introduction rate is 0.5-1 vvm, and the fermentation temperature is 30-45℃.

[0014] Preferably, in step (2) of the above technical solution, the microwave irradiation treatment process is as follows: frequency 900-2500MHz, power 500-800W, temperature 400-600℃, and time 15-30min. This invention uses microwave heat treatment after initial impurity removal, which can further vaporize and decompose organic impurities such as binders instantly, removing obstacles for subsequent flotation. Simultaneously, it exposes the graphite encased in organic matter and the fine impurities adhering to the graphite, creating conditions for subsequent crushing and flotation separation. Furthermore, it can decompose the lithium remaining between graphite layers, laying the foundation for subsequent graphite structure repair.

[0015] Preferably, in step (3) of the above technical solution, the Dv50 particle size of the heat-treated tailings after crushing is controlled at 15-20μm.

[0016] Preferably, in step (3) of the above technical solution, the inhibitor is lime or water glass, and the dosage is 300-600g / t; the collector is kerosene or stearic acid, and the dosage is 200-500g / t; the foaming agent is No. 2 oil, and the dosage is 50-100g / t.

[0017] Preferably, in step (3) of the above technical solution, the specific process of flotation is as follows: the heat treatment tailings are prepared into a slurry with a solid content of 30-40%, the pH is adjusted to 1-2, an inhibitor is added and stirred for 3-5 minutes, a collector is added and stirred for 8-15 minutes, a frother is added, the mixture is stirred evenly, and then poured into the flotation column for aeration, foaming is scraped off, and the frothy concentrate is collected.

[0018] Preferably, in step (4) of the above technical solution, the spray drying process is as follows: the feed rate is 300-400 mL / min, the inlet temperature is 150-200℃, and the outlet temperature is 50-100℃. The spray drying process used in this technical solution allows the graphite powder to re-aggregate. The gaps formed between the small particles after agglomeration, after subsequent high-temperature treatment, create certain pores, which is beneficial for improving the energy storage capacity of the battery.

[0019] Preferably, in step (5) of the above technical solution, the biomass carbon precursor is lignin sulfonate or cellulose derivative, and its usage is 2-4% of the graphite powder.

[0020] Preferably, in step (5) of the above technical solution, the microwave heating treatment process is as follows: frequency of 900-2500MHz, power of 1000-1200W, temperature of 500-800℃, and time of 5-10min. In this technical solution, by selecting a higher power microwave heating treatment process, not only can a small amount of organic impurities introduced by the flotation process be removed, but the crystal structure of graphite can also be further repaired, internal stress eliminated, and its electrochemical performance improved. At the same time, the introduced biomass carbon precursor forms a thin and dense coating layer on the graphite surface and connects the graphite particles, improving conductivity.

[0021] Advantages compared to existing technologies:

[0022] This invention employs a combined process of "bio-fermentation + microwave activation + flotation + microwave remediation." First, inorganic acids (such as sulfuric acid) and organic acids (such as citric acid and oxalic acid) produced by the metabolism of composite microorganisms selectively dissolve and remove metallic impurities such as cobalt, nickel, manganese, and lithium from the surface and interlayers of graphite. Simultaneously, the microorganisms have a certain biodegradation effect on the organic binder, achieving preliminary impurity removal under mild conditions. Then, utilizing the instantaneous heating characteristic of microwaves, residual organic binders and other organic matter are further vaporized and decomposed, rapidly escaping from the graphite interlayers. This also dissociates inorganic impurities into smaller particles, facilitating subsequent impurity removal. Through flotation, residual inorganic impurities are separated from the graphite, further improving graphite purity. The flotation-enriched graphite is then spray-dried to re-aggregate. Finally, microwave treatment decomposes trace impurities introduced by flotation while promoting graphite structural rearrangement, repairing lattice defects, and forming an amorphous carbon coating layer on the graphite surface. The resulting regenerated graphite has a smooth surface and a purity of over 99.5%.

[0023] The recycling process of this invention organically combines biological, physical, and chemical processes. The process is simple, energy-efficient, and environmentally friendly. The resulting recycled graphite has high purity, high initial efficiency and specific capacity, and excellent electrochemical performance, and can be directly used in the production of anode materials. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention for recovering graphite materials from waste power battery tailings;

[0025] Figure 2 The images show SEM images of the recycled graphite obtained in Example 1 of this invention and the graphite in the battery tailings, where a is the recycled graphite obtained in Example 1 and b is the graphite in the battery tailings.

[0026] Figure 3 The image shows the XRD pattern of the recycled graphite obtained in Example 1 of this invention. Detailed Implementation

[0027] The above-described technical features of the present invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. However, the present invention is not limited to these embodiments, nor are these embodiments limited in any way.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the formulations involved in the following examples are all commercially available products and can be purchased from the market.

[0029] The compound functional bacterial groups *Acidithiobacillus ferrooxidans*, *Leymus sulfideus*, and *Aspergillus niger* used in this invention were all purchased from the National Standards Network and were expanded to OD values ​​before use. 600 = 1.

[0030] The culture medium used consisted of 3 g / L ammonium sulfate, 0.4 g / L potassium dihydrogen phosphate, 0.5 g / L magnesium sulfate, 0.1 g / L potassium chloride, 0.05 g / L calcium chloride, 8 g / L sodium thiosulfate, 25 g / L ferrous sulfate, 15 g / L sucrose, with the remainder being distilled water. The pH was adjusted to 1.5-2.5 with sulfuric acid.

[0031] The present invention will be further described in detail below with reference to embodiments:

[0032] Example 1

[0033] A method for recovering graphite materials from waste power battery tailings includes the following steps:

[0034] (1) The battery tail residue after the recycled lithium iron phosphate battery material is crushed and separated is added to a culture medium containing a composite functional bacterial group (Acidobacterium ferrooxidans, Fermentatus sulfideus and Aspergillus niger in a volume ratio of 1.5:1:1). After mixing evenly, air is introduced at a rate of 0.5 vvm. Fermentation is carried out at 30-35℃ for 4 days, and then the air is stopped and fermentation is carried out at 40-45℃ for 3 days. The fermentation tail residue is separated. The corresponding metal can be recovered from the fermentation filtrate as appropriate.

[0035] (2) The fermentation tailings obtained in step (1) were microwave irradiated for 30 minutes under nitrogen protection at a frequency of 2450MHz, a power of 500W, and a temperature of 400℃ to obtain heat-treated tailings.

[0036] (3) After crushing the heat treatment tailings obtained in step (2) (Dv50 particle size controlled at 15-20μm), add it to the mixing tank, add water to adjust the heat treatment tailings into a slurry with a solid content of 30%, adjust the pH to 1-2, add 300g / t of lime and stir for 3min, then add 300g / t of kerosene and continue stirring for 8min, then add 50g / t of No. 2 oil, stir evenly, pour into the flotation column, ventilate, scrape the foam, collect the foam concentrate, and obtain graphite slurry.

[0037] (4) The graphite slurry obtained in step (3) is spray-dried at a feed rate of 300 mL / min, an inlet temperature of 150-200℃, and an outlet temperature of 50-100℃ to obtain graphite powder.

[0038] (5) Mix the graphite powder obtained in step (4) with 2% sulfonated lignin evenly, and microwave heat it under nitrogen protection at a frequency of 2450MHz, a power of 1000W, a temperature of 600℃ and a time of 10min. After cooling, regenerated graphite is obtained.

[0039] Example 2

[0040] A method for recovering graphite materials from waste power battery tailings includes the following steps:

[0041] (1) The battery tail residue after the recycled lithium iron phosphate battery material is crushed and separated is added to a culture medium containing a composite functional bacterial group (Acidobacterium ferrooxidans, Fermentatus sulfideus and Aspergillus niger in a volume ratio of 2:1:1). After mixing evenly, air is introduced at a rate of 0.8 vvm. Fermentation is carried out at 30-35℃ for 3 days, and then the air is stopped and fermentation is carried out at 40-45℃ for 4 days. The fermentation tail residue is separated. The corresponding metal can be recovered from the fermentation filtrate as appropriate.

[0042] (2) The fermentation tailings obtained in step (1) were microwave irradiated for 25 minutes under nitrogen protection at a frequency of 2450MHz, a power of 600W, and a temperature of 500℃ to obtain heat-treated tailings.

[0043] (3) After crushing the heat treatment tailings obtained in step (2) (Dv50 particle size controlled at 15-20μm), add it to the mixing tank, add water to adjust the heat treatment tailings into a slurry with a solid content of 35%, adjust the pH to 1-2, first add 400g / t of lime and stir for 4min, then add 400g / t of kerosene and continue stirring for 10min, then add 60g / t of No. 2 oil, stir evenly, pour into the flotation column, ventilate, scrape the foam, collect the foam concentrate, and obtain graphite slurry.

[0044] (4) The graphite slurry obtained in step (3) is spray-dried at a feed rate of 350 mL / min, an inlet temperature of 150-200℃, and an outlet temperature of 50-100℃ to obtain graphite powder.

[0045] (5) The graphite powder obtained in step (4) is mixed evenly with 3% cellulose and microwave heated under nitrogen protection at a frequency of 2450MHz, a power of 1100W, a temperature of 700℃ and a time of 8min. After cooling, recycled graphite is obtained.

[0046] Example 3

[0047] A method for recovering graphite materials from waste power battery tailings includes the following steps:

[0048] (1) The battery tail residue after the recycled lithium iron phosphate battery material is crushed and separated is added to a culture medium containing a composite functional bacterial group (Acidobacterium ferrooxidans, Fermentatus sulfideus and Aspergillus niger in a volume ratio of 2.5:1:1). After mixing evenly, air is introduced at a rate of 1 vvm. Fermentation is carried out at 30-35℃ for 2 days, and then the air is stopped and fermentation is carried out at 40-45℃ for 4 days. The fermentation tail residue is separated. The corresponding metal can be recovered from the fermentation filtrate as appropriate.

[0049] (2) The fermentation tailings obtained in step (1) were microwave irradiated for 15 minutes under nitrogen protection at a frequency of 2450MHz, a power of 800W, and a temperature of 600℃ to obtain heat-treated tailings.

[0050] (3) After crushing the heat treatment tailings obtained in step (2) (Dv50 particle size controlled at 15-20μm), add it to the mixing tank, add water to adjust the heat treatment tailings into a slurry with a solid content of 40%, adjust the pH to 1-2, add 600g / t of lime and stir for 5min, then add 500g / t of kerosene and continue stirring for 8-15min, then add 100g / t of No. 2 oil, stir evenly, pour into the flotation column, ventilate, scrape the foam, collect the foam concentrate, and obtain graphite slurry.

[0051] (4) The graphite slurry obtained in step (3) is spray-dried at a feed rate of 400 mL / min, an inlet temperature of 150-200℃, and an outlet temperature of 50-100℃ to obtain graphite powder.

[0052] (5) The graphite powder obtained in step (4) is mixed evenly with 4% sulfonated lignin and microwave heated under nitrogen protection at a frequency of 2450MHz, a power of 1200W, a temperature of 800℃ and a time of 5min. After cooling, recycled graphite is obtained.

[0053] Comparative Example 1

[0054] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that, in step (1), the composite functional microbial community is a mixture of *Thiobacillus ferrooxidans* and *Aspergillus niger* in a volume ratio of 1.5:1.

[0055] Comparative Example 2

[0056] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that, in step (1), fermentation is carried out at a temperature of 30°C for 7 days.

[0057] Comparative Example 3

[0058] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that, in step (1), fermentation is carried out at a temperature of 45°C for 7 days.

[0059] Comparative Example 4

[0060] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that step (1) is omitted, and the battery tailings are directly subjected to microwave irradiation treatment.

[0061] Comparative Example 5

[0062] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that step (2) is omitted, and the fermentation tailings are directly subjected to flotation.

[0063] Comparative Example 6

[0064] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that step (3) is omitted, and the heat-treated tailings are directly rinsed with water twice.

[0065] Comparative Example 7

[0066] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that step (4) is omitted, and graphite slurry is directly mixed with sulfonated lignin and microwaved for processing.

[0067] Comparative Example 8

[0068] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that, in step (5), the graphite powder is directly added via microwave treatment.

[0069] Comparative Example 9

[0070] A method for recovering graphite materials from waste power battery tailings differs from Example 1 in that step (5) is omitted, and the graphite powder is the recovered graphite.

[0071] Test case

[0072] 1. The impurities, organic matter, and elements in the graphite slag from the recycled graphite and battery tailings obtained in Example 1 were detected by SEM and XRD. The results are shown in Table 1 and... Figures 2 to 3 As shown.

[0073] Table 1 Comparison of impurity element content (wt.%)

[0074]

[0075] As can be seen from the results in Table 1, the regenerated graphite obtained by the recycling method of this invention has a significantly reduced amount of impurity elements. The XRD pattern also shows that the peaks are mainly graphite, indicating high purity. In addition, the SEM image also shows that after the graphite is purified and recycled, most of the surface impurities are removed, resulting in a smoother surface and higher purity, which is beneficial to the improvement of electrochemical performance.

[0076] 2. The purity of the recycled graphite obtained in Comparative Examples 1-3 and Comparative Examples 1-9 was tested, and its electrochemical performance was also tested. The results are shown in Table 2. The electrochemical performance testing method was as follows: Recycled graphite materials, conductive carbon black SP, CMC, and SBR obtained in each example and comparative example were weighed according to a mass ratio of 95:2:1.5:1.5, stirred evenly in water to form a slurry, and coated onto both sides of a copper foil using a coater. The coated electrodes were then dried in a vacuum drying oven at 110℃ for 2 hours, and then pressed into negative electrodes. The electrolyte composition (volume ratio) was EC:EMC:DNC = 1:1:1, containing 1 mol / L LiPF6, with lithium metal as the counter electrode, and a CR-2420 coin cell was fabricated. Charge-discharge tests were performed on a Blue Battery test cabinet with a voltage range of 0.005-1.0V and a charge-discharge rate of 0.1C to obtain the initial discharge capacity and initial coulombic efficiency.

[0077] Table 2 Graphite purity and electrochemical performance results

[0078]

[0079] As can be seen from the results in Table 2, the recycled graphite obtained by the recycling method of the present invention in Examples 1-3 has relatively high purity, indicating that the recycling method of the present invention is feasible, can effectively remove impurities from battery tailings, and when directly used in lithium-ion batteries, its initial discharge specific capacity is above 380 mAh / g, and the initial coulombic efficiency reaches 94.4%, demonstrating excellent electrochemical performance. In contrast, in Comparative Examples 1-9, changes in recycling process conditions or process omissions all affected the purity and electrochemical performance of the recycled graphite to some extent. This further illustrates the feasibility and advantages of the recycling method of the present invention, where each step and reaction condition is synergistic and has a certain impact on the performance of the recycled product.

[0080] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering a graphite material from tailings of a spent power battery, characterized by, The method comprises the following steps: (1) adding battery tailings into a culture solution containing a composite functional bacterial population, mixing uniformly, passing in air, and fermenting at 30-35 DEG C for 2-4 days, stopping passing in air, and continuing to ferment at 40-45 DEG C for 3-4 days, and separating to obtain fermented tailings; the composite functional bacterial population is a mixed bacteria of Thiobacillus ferroxidans, Sulfolobus and Aspergillus niger with a volume ratio of 1.5-2.5:1:1; (2) treating the fermented tailings obtained in step (1) under microwave irradiation under nitrogen protection to obtain heat-treated tailings; (3) crushing the heat-treated tailings obtained in step (2), adding water, inhibitor, collector and frother, mixing uniformly in a stirring tank, and then entering a flotation column for flotation separation to obtain graphite slurry; (4) spray drying the graphite slurry obtained in step (3) to obtain graphite powder; (5) mixing the graphite powder obtained in step (4) with a biomass carbon precursor, and performing microwave heating treatment under nitrogen protection, and cooling to obtain regenerated graphite.

2. The method according to claim 1, wherein the method is characterized by, In step (1), the inoculation amount of the composite functional bacterial population is 5-8% of the total amount of the culture solution; and the solid-liquid ratio of the battery tailings to the culture solution is 1:5-8.

3. The method according to claim 1 or 2, characterized in that, The components of the culture solution include ammonium sulfate 2-4 g / L, potassium dihydrogen phosphate 0.3-0.5 g / L, magnesium sulfate 0.4-0.7 g / L, potassium chloride 0.1-0.2 g / L, calcium chloride 0.02-0.05 g / L, sodium thiosulfate 5-10 g / L, ferrous sulfate 10-30 g / L, sucrose 8-20 g / L, and the balance is distilled water; and the air passing-in speed is 0.5-1 vvm.

4. The method according to claim 1, wherein the method is characterized by, In step (2), the microwave irradiation treatment process is as follows: frequency 900-2500 MHz, power 500-800 W, temperature 400-600 DEG C, and time 15-30 min.

5. The method according to claim 1, wherein the method is characterized by, In step (3), the Dv50 particle size of the crushed heat-treated tailings is controlled at 15-20 μm.

6. The method of claim 1, wherein the tailings are from a spent power battery. In step (3), the inhibitor is lime or water glass, and the amount used is 300-600 g / t; the collector is kerosene or stearic acid, and the amount used is 200-500 g / t; and the frother is No. 2 oil, and the amount used is 50-100 g / t.

7. The method according to claim 1, wherein the method is characterized by, In step (3), the specific process of flotation is as follows: the heat-treated tailings are adjusted into slurry with a solid content of 30-40%, the pH is adjusted to 1-2, the inhibitor is added first and stirred for 3-5 min, then the collector is added and stirred for 8-15 min, the frother is added, the mixture is stirred uniformly, and then poured into the flotation column for aeration, froth scraping and collection of froth concentrate.

8. The method for recovering graphite materials from waste power battery tailings according to claim 1, characterized in that, In step (4), the process of spray drying is as follows: the feeding speed is 300-400 mL / min, the inlet temperature is 150-200 DEG C, and the outlet temperature is 50-100 DEG C.

9. A method for recovering graphite materials from waste power battery tailings according to claim 1, characterized in that, In step (5), the biomass carbon precursor is lignin sulfonate or cellulose derivative, and the amount used is 2-4% of the graphite powder.

10. A method for recovering graphite materials from waste power battery tailings according to claim 1, characterized in that, In step (5), the microwave heating treatment process is as follows: frequency 900-2500 MHz, power 1000-1200 W, temperature 600-800 DEG C, and time 5-10 min.

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