Waste lithium battery graphite regeneration method and system based on photo-electro-chemical catalytic oxidation
By using a photo-electro-chemical catalytic oxidation method, the problems of high pollution, high energy consumption, and low value in the recycling of graphite from waste lithium batteries have been solved, and the preparation of high-performance recycled graphite has been achieved, which is suitable for the manufacture of new batteries.
Patent Information
- Application Number
- CN202511963150.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-06
AI Technical Summary
Existing technologies for recycling graphite from waste lithium batteries suffer from high pollution, high energy consumption, and low value. They are also unable to effectively remove impurities from the graphite surface and between layers, resulting in poor performance of recycled graphite that cannot be directly used in the manufacture of new batteries.
A photo-electro-chemical catalytic oxidation method was adopted, in which the photoelectrochemical oxidation reaction was carried out in a non-alkaline electrolyte solution of 0.05-0.5 mol/L under a forward bias voltage of 0.5-1.5V and light irradiation. Subsequently, heat treatment was carried out in an inert atmosphere to remove the residues on the graphite surface and between the layers and restore its performance.
It achieves efficient and low-energy removal of surface and interlayer impurities in graphite, resulting in high-performance regenerated graphite with an ID/IG value ≤0.20 in Raman spectroscopy, a powder conductivity ≥2.0 S/cm, and an initial coulombic efficiency ≥92%, meeting the requirements for battery-grade applications.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of photoelectrocatalysis technology, and in particular to a method and system for regenerating graphite from waste lithium batteries based on photo-electro-chemical catalytic oxidation. Background Technology
[0002] With the rapid development of the electric vehicle and energy storage industries, the consumption and disposal of lithium-ion batteries are growing exponentially. Currently, global research and development of battery recycling technology and industrial layout mainly focus on recovering high-value metals such as cobalt, nickel, and lithium from cathode materials, and relatively mature hydrometallurgical processes have been developed. However, the recycling value and technology of graphite anodes, which account for about 12%-15% of battery weight, have long been neglected. They are usually landfilled as waste or subjected to low-value-added "downgraded recycling," which not only wastes valuable carbon resources but also brings potential environmental risks.
[0003] The conventional methods for recovering graphite anodes mainly include the following aspects: (1) Used as a carbon raiser, graphite anode is added to the pyrometallurgical process as a reducing agent or flux. Graphite is burned or consumed as a reducing agent at high temperatures, and the final product is no longer a functional material, completely losing its value as a battery material. However, this method of recycling graphite is cost-effective and generates a large amount of waste. ; (2) Soaking the negative electrode black powder with strong acids (such as hydrochloric acid and sulfuric acid) or strong alkalis can dissolve and remove metallic impurities and some organic matter. However, the effect on removing the dense and stable solid electrolyte interphase (SEI) film on the graphite surface and lithium compounds embedded in the graphite layers is limited. However, the indiscriminate use of strong oxidizing acids (such as sulfuric acid) may oxidize and corrode the graphite skeleton and damage it. Hybrid structure leads to permanent capacity loss and poor recovery of electrochemical performance of regenerated graphite; (3) High-temperature heat treatment technology is used to treat graphite, but heat treatment affects the inorganic components in the SEI film. The removal effect is not ideal, and these residues will seriously hinder the insertion / extraction of lithium ions, affecting rate performance and cycle life. Furthermore, PVDF may carbonize at high temperatures to form amorphous carbon, which covers the graphite surface and blocks lithium ion channels.
[0004] In summary, existing technologies for processing waste graphite anodes generally suffer from the drawbacks of "high pollution, high energy consumption, and low value." Therefore, the industry urgently needs a technology that can regenerate waste, degraded graphite into high-performance anode materials that can be directly used in the manufacture of new batteries. Summary of the Invention
[0005] To address the technical problems existing in the background art, this invention proposes a method for regenerating graphite from spent lithium batteries based on photo-electro-chemical catalytic oxidation, comprising the following steps: The graphite rough material is mixed with a 0.05-0.5 mol / L non-alkaline electrolyte solution and subjected to photoelectrocatalytic oxidation under a positive bias voltage of 0.5-1.5V and light irradiation. Solid-liquid separation is performed to obtain a regenerated graphite precursor, which is then heat-treated under an inert atmosphere to obtain regenerated graphite.
[0006] In this invention, the combined photoelectrocatalytic conditions, such as a forward bias voltage of 0.5-1.5V, a non-alkaline electrolyte solution of 0.05-0.5mol / L, and synergistic effect of light, can stably repair graphite in waste lithium batteries, remove residues (organic impurities or SEI film, etc.) from the graphite surface and interlayer voids, and obtain high-performance regenerated graphite. Furthermore, due to the special structure of graphite, the anode bias voltage, electrolyte type, and light are all key and non-obvious process parameters. Any single condition deviating from the range defined in this invention will significantly reduce the regeneration effect of graphite and may even damage the inherent structure of graphite.
[0007] Preferably, the graphite rough material is obtained by ultrasonically peeling off waste lithium battery negative electrode sheets in a solvent; More preferably, the solvent is deionized water or N-methylpyrrolidone; More preferably, the ultrasonic power is 200-600W and the ultrasonic time is 10-60min.
[0008] In this invention, ultrasonic treatment of graphite in a solvent can peel the active material off the copper foil current collector to obtain the graphite coarse material.
[0009] Preferably, the non-alkaline electrolyte solution is an acidic electrolyte solution or a neutral electrolyte solution; More preferably, the acidic electrolyte solution is a 0.1 mol / L sulfuric acid solution; More preferably, the neutral electrolyte solution is a 0.1 mol / L sodium sulfate solution.
[0010] In this invention, selecting the acidic electrolyte solution not only promotes the effect of photoelectrocatalysis but also promotes the dissolution of metal impurities.
[0011] Preferably, the forward bias voltage is 0.8-1.2V.
[0012] Preferably, the light intensity is 50-200 mW / cm²; More preferably, the light intensity is 80-150 mW / cm².
[0013] Preferably, the photoelectrocatalytic oxidation reaction time is 0.5-5 hours; More preferably, the photoelectrocatalytic oxidation reaction time is 1-3 hours.
[0014] In this invention, the illumination can generate a large number of electron-hole pairs while reducing power consumption; and the applied anodic bias voltage forms a built-in electric field inside the semiconductor. On the one hand, this electric field can forcibly separate photogenerated electrons and holes, greatly suppressing their recombination probability, which can effectively solve the limitations of simple photocatalysis, thereby multiplying the number of holes available for oxidation reaction and increasing the reaction efficiency by orders of magnitude. On the other hand, the electric field can drive negatively charged intermediate products, optimize the reaction path, and accelerate the reaction efficiency.
[0015] Preferably, the heat treatment temperature is 700-900℃ and the heat treatment time is 1-3h.
[0016] In this invention, heat treatment in an inert atmosphere (argon or nitrogen) can effectively eliminate the very small amount of structural stress that may be generated during photoelectrocatalysis, further order the carbon layer arrangement (increase the degree of graphitization), and ensure that the recycled material has excellent conductivity and structural stability.
[0017] The present invention also proposes a system for the above-mentioned method of regenerating graphite from waste lithium batteries based on photo-electro-chemical catalytic oxidation, the system comprising a reaction tank with a light-transmitting window on at least one side, a photoanode, a counter electrode, a light source, a potentiostat, and a magnetic stirrer; Preferably, the reaction tank is an H-type dual-chamber reaction tank, with the photoanode chamber and the counter electrode chamber separated by a Nafion 117 proton exchange membrane; Preferably, the light-transmitting window is made of quartz or high-transmittance glass; Preferably, the photoanode and counter electrode are both inside the reaction tank, and the potentiostat is connected to the photoanode and counter electrode.
[0018] Preferably, the counter electrode is any one of a platinum electrode, a stainless steel mesh, or a graphite rod; Preferably, the photoanode is a semiconductor electrode; More preferably, the semiconductor electrode is a TiO2 nanotube array, a WO3 nanosheet, or a BiVO4 / CoOx heterojunction electrode, which is used as a photoanode; More preferably, the diameter of the TiO2 nanotube array is 80-150 nm and the length is 1-5 μm. Preferably, the light source is an ultraviolet LED array with an emission wavelength of 365nm, or a visible blue LED array with an emission wavelength range of 400-500nm; In this invention, the emission spectrum of the light source matches the absorption spectrum of the photoanode. When light of a specific wavelength irradiates the semiconductor electrode, it excites its valence band electrons to jump to the conduction band, generating a high-energy electron and a positively charged hole. The hole has a very strong oxidizing ability and can directly capture electrons from organic molecules adsorbed on the electrode surface, causing them to undergo oxidative decomposition. The hole or excited-state electron can react with water molecules or hydroxide ions in the solution to generate hydroxyl radicals. Hydroxyl radicals can indiscriminately oxidize most organic substances, ultimately mineralizing them into carbon dioxide, water, or inorganic small molecules. In this invention, since there are impurities such as SEI film, polymer and inorganic lithium salt on the surface or in the interlayer voids of graphite rough, graphite regeneration is to remove these impurities. Since these impurities have higher reactivity and weaker chemical bonds than the graphite bulk, they will preferentially react with holes or hydroxyl radicals. After graphite regeneration, its graphite bulk structure is preserved.
[0019] Beneficial effects of this invention: (1) Light energy drives the photoanode to generate high-energy electrons and positively charged holes, which greatly reduces energy consumption; (2) Utilize the highly active oxide species (holes, hydroxyl radicals) generated by photoelectrocatalysis to selectively decompose organic impurities and stubborn SEI films on the graphite surface, avoiding damage to the main structure of graphite; (3) Through the synergistic effect of "photo-electro-chemistry", the graphite material is deeply purified and its structure is repaired. The resulting recycled graphite has an ID / IG value of ≤0.20 in Raman spectrum, a powder conductivity of ≥2.0S / cm, an initial coulombic efficiency of ≥92%, and an initial discharge specific capacity of not less than 320mAh / g at a 0.2C rate. This recycled graphite is of excellent quality and has stable performance, which can meet the requirements of battery-grade applications. Detailed Implementation
[0020] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
[0022] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.
[0023] Example 1
[0024] This embodiment proposes a method and system for regenerating graphite from spent lithium batteries based on photo-electro-chemical catalytic oxidation. The specific steps are as follows: (1) After discharging and disassembling the recycled waste lithium battery, the negative electrode sheet is placed in N-methylpyrrolidone and ultrasonically treated. The ultrasonic treatment power is 400W and the treatment time is 30min, so that the active material is peeled off from the copper foil current collector to obtain graphite coarse material. (2) Place the graphite coarse material in the reaction tank of the photoelectrocatalytic reactor. The reaction tank is an H-type double-chamber reaction tank. The photoanode chamber and the counter electrode chamber are separated by a Nafion 117 proton exchange membrane. Add 0.1 mol / L sodium sulfate solution to the reaction tank. Use TiO2 nanotube array (nanotube diameter is 100 nm and tube length is 3 μm) as photoanode and platinum sheet electrode as counter electrode. Connect a potentiostat to the photoanode and counter electrode to provide a stable forward bias voltage of 1.0 V. Use an ultraviolet LED array with an emission wavelength of 365 nm as the light source. Apply light with an intensity of 100 mW / cm² from the light transmission window. Start the magnetic stirrer to stir the mixture in the reaction tank and carry out the photoelectrocatalytic oxidation reaction for 2 hours. (3) Filter the mixture in the reaction tank, wash the obtained solid with deionized water until neutral, and dry it to obtain the regenerated graphite precursor; (4) The recycled graphite precursor was heated at 800°C for 2 hours under argon protection to obtain recycled graphite.
[0025] Example 2
[0026] This embodiment proposes a method and system for regenerating graphite from spent lithium batteries based on photo-electro-chemical catalytic oxidation. The specific steps are as follows: (1) After discharging and disassembling the recycled waste lithium battery, the negative electrode sheet is placed in N-methylpyrrolidone and ultrasonically treated. The ultrasonic treatment power is 400W and the treatment time is 30min, so that the active material is peeled off from the copper foil current collector to obtain graphite coarse material. (2) Place the graphite coarse material in the reaction tank of the photoelectrocatalytic reactor. The reaction tank is an H-type double-chamber reaction tank. The photoanode chamber and the counter electrode chamber are separated by a Nafion 117 proton exchange membrane. Add 0.1 mol / L sulfuric acid solution to the reaction tank. Use TiO2 nanotube array (nanotube diameter is 100 nm and tube length is 3 μm) as photoanode and platinum sheet electrode as counter electrode. Connect a potentiostat to the photoanode and counter electrode to provide a stable forward bias voltage of 1.0 V. Use an ultraviolet LED array with an emission wavelength of 365 nm as the light source. Apply light with an intensity of 100 mW / cm² from the light transmission window. Start the magnetic stirrer to stir the mixture in the reaction tank and carry out the photoelectrocatalytic oxidation reaction for 2 hours. (3) Filter the mixture in the reaction tank, wash the obtained solid with deionized water until neutral, and dry it to obtain the regenerated graphite precursor; (4) The recycled graphite precursor was heated at 800°C for 2 hours under argon protection to obtain recycled graphite.
[0027] Example 3
[0028] This embodiment proposes a method and system for regenerating graphite from spent lithium batteries based on photo-electro-chemical catalytic oxidation. The specific steps are as follows: (1) After discharging and disassembling the recycled waste lithium battery, the negative electrode sheet is placed in N-methylpyrrolidone and ultrasonically treated. The ultrasonic treatment power is 400W and the treatment time is 30min, so that the active material is peeled off from the copper foil current collector to obtain graphite coarse material. (2) Place the graphite coarse material in the reaction tank of the photoelectrocatalytic reactor. The reaction tank is an H-type double-chamber reaction tank. The photoanode chamber and the counter electrode chamber are separated by a Nafion 117 proton exchange membrane. Add 0.1 mol / L sodium sulfate solution to the reaction tank. Use TiO2 nanotube array (nanotube diameter is 100 nm and tube length is 3 μm) as photoanode and platinum sheet electrode as counter electrode. Connect a potentiostat to the photoanode and counter electrode to provide a stable forward bias voltage of 0.8 V. Use an ultraviolet LED array with an emission wavelength of 365 nm as the light source. Apply light with an intensity of 100 mW / cm² from the light transmission window. Start the magnetic stirrer to stir the mixture in the reaction tank and carry out the photoelectrocatalytic oxidation reaction for 2 h. (3) Filter the mixture in the reaction tank, wash the obtained solid with deionized water until neutral, and dry it to obtain the regenerated graphite precursor; (4) The recycled graphite precursor was heated at 800°C for 2 hours under argon protection to obtain recycled graphite.
[0029] Comparative Example 1 This comparative example proposes a method and system for regenerating graphite from waste lithium batteries. The specific steps are the same as in Example 1, except that "provide a stable forward bias voltage of 0.8V" in step (2) is replaced with "provide a stable forward bias voltage of 0.3V".
[0030] Comparative Example 2 This comparative example proposes a method and system for regenerating graphite from waste lithium batteries. The specific steps are the same as those in Example 1, except that in step (2), "add 0.1 mol / L sodium sulfate solution to the reaction tank" is replaced with "add 0.1 mol / L sodium potassium hydroxide solution to the reaction tank".
[0031] Comparative Example 3 This comparative example proposes a method and system for the graphite recycling of waste lithium batteries. The specific steps are the same as those in Example 1, except that in step (2), "the light source applies light with an intensity of 100mW / cm² through the light-transmitting window" is replaced with "the light source is turned off, there is no light, and it remains completely dark".
[0032] Application examples 80 mg of recycled graphite obtained in Examples 1-3 and Comparative Examples 1-3, 10 mg of acetylene black (conductive agent), and 10 mg of PVDF were weighed out respectively. N-methylpyrrolidone was added to form a paste, which was then uniformly coated onto copper foil. The coated copper foil was vacuum dried at 60°C for 12 hours, and then pressed into a negative electrode sheet using a tablet press at 10 MPa. A lithium metal sheet was used as the positive electrode sheet, Celgard 2400 as the separator, and a 1 mol / L LiPF6 solution was used as the electrolyte. The solvent was a mixture of EC, DMC, and EMC in a volume ratio of 1:1:1. A CR2032 button half-cell was assembled in an argon glove box (H2O, O2 < 0.1 ppm) and electrochemical tests were performed. Raman ID / IG value: Tested using a laser Raman spectrometer, a smaller ID / IG value indicates a higher degree of graphitization in the material, and a more complete, ordered crystal structure with fewer defects; Powder conductivity: Take 1g of sample and place it in the mold. Apply pressure and collect the powder conductivity at 200mPa using a four-probe powder conductivity meter. The higher the conductivity, the less the deposits are on the surface of the recycled graphite and in the gaps between the graphite sheets, that is, the better the recycling effect. First coulombic efficiency and first discharge specific capacity: The batteries prepared in each example and comparative example were subjected to a complete charge-discharge cycle at a rate of 0.2C to obtain the charge specific capacity and discharge specific capacity, and their first coulombic efficiency was calculated. The electrochemical performance of recycled graphite was comprehensively analyzed based on the above test results, and the specific results are shown in Table 1: Table 1. Electrochemical performance test results of recycled graphite in each example and comparative example.
[0033] As can be seen from the results of Examples 1-3 and Comparative Examples 1-3, the setting of the core parameters in this invention is not obvious. Among them, the three conditions of anode bias, electrolyte type and light are indispensable. Any single condition deviating from the limit range will lead to a significant decrease in the repair effect or damage to the graphite body.
[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for recycling spent lithium battery graphite based on photo-electro-chemical catalytic oxidation, characterized in that, The method comprises the following steps: The graphite crude material is mixed with a non-alkaline electrolyte solution with a concentration of 0.05-0.5 mol / L, and then photoelectrocatalytic oxidation is carried out under a forward bias of 0.5-1.5 V and light irradiation, and a regenerated graphite precursor is obtained through solid-liquid separation, and then the regenerated graphite precursor is heat-treated in an inert atmosphere to obtain regenerated graphite. 2.The method for regenerating waste lithium battery graphite based on photo-electro-chemical catalytic oxidation according to claim 1, characterized in that, The graphite crude material is obtained by ultrasonic exfoliation of waste lithium battery negative electrode sheets in a solvent; Preferably, the solvent is deionized water or N-methyl pyrrolidone; Preferably, the ultrasonic power is 200-600 W, and the ultrasonic time is 10-60 min. 3.The method of claim 1 or 2, wherein the method further comprises the step of, The non-alkaline electrolyte solution is an acidic electrolyte solution or a neutral electrolyte solution; Preferably, the acidic electrolyte solution is a 0.1 mol / L sulfuric acid solution; Preferably, the neutral electrolyte solution is a 0.1 mol / L sodium sulfate solution.
4. The method for regenerating waste lithium battery graphite based on photo-electro-chemical catalytic oxidation according to any one of claims 1-3, characterized in that, The forward bias is 0.8-1.2 V.
5. The method for regenerating waste lithium battery graphite based on photo-electro-chemical catalytic oxidation according to any one of claims 1-4, characterized in that, The light intensity is 50-200 mW / cm²; Preferably, the light intensity is 80-150 mW / cm².
6. The method for regenerating waste lithium battery graphite based on photo-electro-chemical catalytic oxidation according to any one of claims 1-5, characterized in that, The photoelectrocatalytic oxidation time is 0.5-5 h; Preferably, the photoelectrocatalytic oxidation time is 1-3 h.
7. The method for regenerating waste lithium battery graphite based on photo-electro-chemical catalytic oxidation according to any one of claims 1-6, characterized in that, The heat treatment temperature is 700-900 ℃, and the heat treatment time is 1-3 h.
8. A system for the regeneration of spent lithium battery graphite based on photo-electro-chemical catalytic oxidation according to any one of claims 1 to 7, characterized in that, The system comprises at least one reaction tank provided with a light-transmitting window, a photoanode, a counter electrode, a light source, a constant potential instrument, and a magnetic stirrer. 9.The system for the method of regenerating spent lithium battery graphite based on photo-electro-chemical catalytic oxidation according to claim 8, wherein, The photoanode and the counter electrode are both inside the reaction tank, and the constant potential instrument is connected to the photoanode and the counter electrode. 10.The system for the method of regenerating spent lithium battery graphite based on photo-electro-chemical catalytic oxidation according to claim 8 or 9, characterized in that, The photoanode is a semiconductor electrode.