A low-temperature stripping method for a lithium battery electrode sheet polyphenol hydroxyl complexing passivation agent

Abstract

The present application belongs to the technical field of lithium ion battery resource recycling, and specifically discloses a low-temperature stripping method for a lithium battery electrode sheet polyphenol hydroxyl complexing passivation agent, which comprises the following steps: preparing a water-based passivation stripping solution with polyphenol hydroxyl compounds, immersing the electrode sheet in the stripping solution, and cooperating with ultrasonic treatment; the polyphenol substance is complexed and passivated with the copper / aluminum current collector surface to form a protective film, thereby reducing the interfacial bonding force between the active material and the metal foil, and the ultrasonic cavitation accelerates the penetration of the reagent to achieve rapid powder removal at room temperature. After stripping, the copper and aluminum foils are complete and unbroken, the active material crystal structure is undamaged, and the content of powder metal impurities is extremely low; the whole process is operated at room temperature, without high temperature, strong acid, strong base, or organic solvent, the process flow is short, the stripping solution can be recycled, and it is green, low-carbon, and low-cost. High-purity active powder and complete metal current collectors can be obtained, and the method has large-scale industrial application value.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery resource recycling technology, and in particular to a low-temperature stripping method for polyphenol hydroxyl complex passivating agents on lithium battery electrode sheets. Background Technology

[0002] With the rapid expansion of the new energy vehicle, large-scale energy storage, and consumer electronics industries, the amount of scrapped lithium-ion batteries is increasing year by year. Retired lithium batteries contain high-value positive and negative electrode active materials, copper and aluminum current collectors, binders, electrolytes, and other components. Efficient and low-damage separation of active materials and metal foil is the core pre-process for battery recycling. Current mainstream electrode powder removal processes are divided into four categories: mechanical crushing and sorting, high-temperature thermal depowdering, strong acid and strong alkali wet leaching, and organic solvent swelling and debinding. Each process has significant drawbacks. Mechanical crushing and sorting process: This process separates black powder from metal foil through multi-stage crushing, screening, air separation, and magnetic separation. It has a large processing capacity, but the mechanical impact can tear copper and aluminum foil, forming tiny metal fragments that mix into the black powder, significantly increasing the metal impurity content of the active powder. At the same time, the crushing force damages the particle morphology and crystal structure of the active material, severely reducing the direct regeneration performance of the cathode material. The entire process involves many pieces of equipment, is lengthy, and has high equipment investment costs.

[0003] High-temperature thermal decomposition powdering process (pyrometallurgical): This process relies on high-temperature decomposition of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) binders to achieve powder removal. However, it suffers from problems such as high energy consumption and stringent requirements for the closed atmosphere control of high-temperature equipment. The thermal decomposition of fluorine-containing binders generates pollutants such as HF, VOCs, and dust, resulting in high costs for exhaust gas treatment. High temperatures can also alter the crystal structure of the cathode material, surface residual alkali, and secondary particle morphology, leading to a significant degradation in the electrochemical performance of recycled materials.

[0004] Strong acid and strong alkali wet treatment process: It relies on acid and alkali corrosion to dissolve aluminum foil and destroy the interfacial bonding force to remove active materials. The process goal is not to preserve the complete structure of current collector and active materials. A large number of metal ions dissolve into the waste liquid, making subsequent solid-liquid separation, solution purification and wastewater treatment processes complicated. High concentrations of acid and alkali will dissolve some active metal elements, reducing the recovery rate of valuable metals and product purity.

[0005] Organic solvent swelling and debinding process: This process uses organic solvents to swell / dissolve PVDF binders to achieve debinding. However, most organic solvents are toxic, flammable and explosive, and solvent distillation recovery is energy-intensive and costly. Different batches of electrode sheets have large differences in compaction density, aging degree and binder ratio. Debinding with a single solvent has poor stability and incomplete powder removal.

[0006] In summary, existing recycling processes generally suffer from drawbacks such as high energy consumption, significant pressure on waste treatment, severe damage to metal current collectors, damage to the crystal structure of active materials, high levels of powder impurities, and lengthy process flows. The industry urgently needs a new low-temperature, water-based, low-damage, and high-efficiency non-destructive stripping technology for lithium battery electrodes. Summary of the Invention

[0007] The purpose of this invention is to provide a low-temperature stripping method for polyphenol hydroxyl complex passivating agents on lithium battery electrode sheets. The method uses an aqueous solution containing polyphenol hydroxyl compounds as the passivation stripping liquid, combined with the synergistic effect of ultrasonic cavitation, to achieve complete separation of the active material layer from the copper / aluminum current collector under normal temperature and mild conditions, while fully preserving the crystal structure of the metal foil and the active material. The process is green, the process is simple, and the stripping efficiency is 100%.

[0008] To achieve the above objectives, the present invention provides a low-temperature stripping method for polyphenol hydroxyl complex passivating agents on lithium battery electrode sheets, comprising the following steps: S1. Provide a lithium battery electrode sheet to be processed. The electrode sheet includes a metal current collector and an active material layer attached to the surface of the metal current collector. The metal current collector is aluminum foil and / or copper foil. S2. Prepare a polyphenol complexing passivation stripping solution, which is an aqueous solution containing a polyphenol hydroxyl complexing passivating agent; S3. Immerse the electrode sheet in the passivation stripping solution; S4. Ultrasonic treatment is applied simultaneously during the infiltration process; S5. Collect the intact metal current collector and the active material powder separately through solid-liquid separation; S6. Post-process the metal current collector and active material powder, and recycle the passivation stripping solution after the pH test meets the standard.

[0009] Preferably, in step S1, the active material layer is selected from one or more of ternary cathode materials, lithium iron phosphate cathode materials, lithium cobalt oxide cathode materials, lithium manganese oxide cathode materials, graphite anode materials, and silicon-carbon anode materials.

[0010] Preferably, in step S2, the polyphenol hydroxy complexing passivating agent includes at least one of tannic acid, gallic acid, tea polyphenols, catechins, and pyrogallic acid.

[0011] Preferably, in step S2, the concentration of the polyphenol hydroxy complex passivating agent in the passivation stripping solution is 0.05–0.1 mol / L, and the pH of the passivation stripping solution is controlled at 3–5.

[0012] Preferably, in step S3, the contact temperature is 15–60°C and the total contact time is 1–5 min.

[0013] Preferably, in step S4, the ultrasonic frequency is 20–40 kHz.

[0014] Preferably, in step S5, the solid-liquid separation method is selected from any one of gravity filtration, vacuum filtration, pressure filtration, centrifugal filtration, membrane filtration, and sedimentation sieving.

[0015] Preferably, in step S6, the post-treatment of the metal current collector includes soaking in clean water, rinsing, ultrasonic cleaning, and low-temperature drying; the post-treatment of the active material powder includes washing with water, low-temperature drying, and sieving to remove impurities; the passivation stripping solution can be directly recycled if the pH is maintained in the range of 3 to 5, and can be reused after adding polyphenol passivating agent to adjust the pH when it deviates from the standard range.

[0016] The advantages and beneficial effects of the low-temperature stripping method for the polyphenol hydroxyl complex passivating agent of lithium battery electrode sheets described above are as follows: 1. This invention uses 0.05mol / L tannic acid aqueous solution to achieve complete de-powdering of positive and negative electrode sheets by ultrasonication at room temperature for 1 to 10 minutes, with a peeling rate of 100%. The entire core process consists of only three steps: "immersion-ultrasonic peeling-solid-liquid separation". The complete process has only 5 steps, which is far fewer than the 7 to 10 steps of mechanical, pyrometallurgical and traditional wet processes, greatly reducing labor time and equipment investment.

[0017] 2. This invention relies on interfacial complexation and passivation to weaken the interfacial bonding force and remove powder, rather than corroding and dissolving the metal foil; after peeling, the copper and aluminum foils maintain the complete roll shape without fragmentation loss; there is no high temperature or strong mechanical impact throughout the process, and the active material particles and crystal lattice are intact without structural damage, making it suitable for high-value direct regeneration processes.

[0018] 3. Compared with mechanical crushing process, this invention eliminates the inclusion of metal foil debris in the active powder; after testing, the residual aluminum impurities in the separated cathode powder are only 0.026 wt%; the active metal leaching rate is extremely low, with Li leaching at 0.21%, Ni at 0.27%, Co at 0.08%, and Mn at 0.17%, significantly improving the recovery rate of valuable metals.

[0019] 4. The stripping medium of this invention is an aqueous solution, which has no organic solvent toxicity or risk of combustion and explosion; no high-temperature heating is required, the energy consumption per unit battery is only 5.84 MJ / kg, and the greenhouse gas emission is 0.61 g / kg, which is low-carbon and environmentally friendly; the passivation stripping solution can be recycled multiple times after passing the test, with low reagent consumption and extremely low waste liquid generation, simplifying the three waste treatment process.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of a low-temperature stripping method for polyphenol hydroxyl complex passivating agents on lithium battery electrode sheets according to the present invention; Figure 2These are actual images of the negative electrode sheet before and after peeling in Example 2 of the present invention; where A is a reaction state diagram of the electrode sheet being immersed in a polyphenol complex passivation peeling solution for ultrasonic peeling; and B is the product obtained after peeling. Figure 3 The current collector is obtained by peeling off the entire roll in Embodiment 2 of the present invention, wherein A is the peeled aluminum foil and B is the peeled copper foil. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0025] Example 1 A non-destructive peeling method for lithium battery electrode sheets based on polyphenol complex passivation solution, such as Figure 1 As shown, it includes the following steps: S1. Pre-treatment material preparation: Provide lithium battery electrode sheets to be processed.

[0026] The electrode sheet consists of a metal current collector and an active material layer attached to the surface of the current collector; the metal current collector is one or a mixture of aluminum foil (positive electrode) and copper foil (negative electrode); the active material layer is selected from one or more of ternary positive electrode materials, lithium iron phosphate positive electrode materials, lithium cobalt oxide positive electrode materials, lithium manganese oxide positive electrode materials, graphite negative electrode materials, and silicon-carbon negative electrode materials.

[0027] The sources of the electrode sheets to be processed include: positive and negative electrode sheets from the dismantling of retired lithium-ion batteries, positive and negative electrode scraps generated during the lithium battery production process, and scrapped / unqualified electrode sheets from production.

[0028] S2. Prepare polyphenol complexing passivation stripping solution.

[0029] The passivation stripping solution is a deionized aqueous solution containing a polyphenolic hydroxy complex passivating agent; the polyphenolic hydroxy complex passivating agent is selected from at least one of tannic acid, gallic acid, tea polyphenols, catechins, and pyrogallol, with tannic acid being preferred.

[0030] The molar concentration of the passivating agent is controlled at 0.05–0.1 mol / L, and the pH of the solution is maintained at 3–5 after preparation.

[0031] S3, the electrode sheet is immersed in and in contact with the passivation stripping solution.

[0032] The electrode sheet is brought into complete contact with the passivation stripping solution by any of the following methods: soaking, spraying, circulating rinsing, or dripping wetting; the reaction temperature is 15–60℃; and the total contact time is 1–10 min.

[0033] S4, complexation passivation and ultrasonic synergistic interface stripping.

[0034] Ultrasonic aid treatment is applied simultaneously during the electrode impregnation process: ultrasonic frequency 20-40kHz.

[0035] Polyphenolic hydroxyl substances undergo adsorption and complexation reactions with metal sites on the surface of copper / aluminum foil, forming a polyphenol-metal complex passivation film on the surface of the current collector. The passivation film has a dual function: inhibiting the continuous corrosion of the metal foil and completely preserving the current collector matrix; and destroying the interfacial forces between the active material, binder and metal foil, thus weakening the interfacial bonding strength.

[0036] Ultrasonic waves generate cavitation in the liquid phase. The bursting of microbubbles creates an impact force that propels the passivation liquid into the microscopic gaps of the active material, accelerating the arrival of polyphenols at the reaction interface. This significantly shortens the passivation film formation and peeling time, allowing the active material to detach completely without mechanical stirring or vibration.

[0037] S5. Solid-liquid separation and collection of stripped products.

[0038] After stripping, the system is divided into two phases: a complete metal current collector and a slurry containing active materials. Separation is achieved by gravity filtration, vacuum filtration, centrifugation, membrane filtration, or sedimentation sieving, and the complete copper / aluminum foil, the active material filter cake, and the passivation stripping mother liquor are collected respectively.

[0039] S6. Product post-treatment and stripping fluid recycling.

[0040] 1) Post-processing of metal current collectors: The collected aluminum / copper foils are soaked in clean water, rinsed, ultrasonically cleaned, and dried at low temperature before being recycled and reused as high-purity metal raw materials.

[0041] 2) Post-processing of active materials: The filter cake of active materials is washed with water, dried at low temperature, and screened to remove impurities, resulting in low-impurity cathode powder / graphite black powder, which can be directly used for battery material regeneration, lithium replenishment repair or hydrometallurgical metal extraction.

[0042] 3) Passivation stripping solution circulation: The pH of the filtered mother liquor is tested. If the pH is maintained in the range of 3 to 5, it can be directly reused for the next batch of stripping. If the pH deviates from the standard range, polyphenol passivating agent is added to adjust the concentration and pH before recycling, which greatly reduces the consumption of reagents and waste liquid discharge.

[0043] Example 2 Preparation of passivation stripping solution: Dissolve 0.85g of tannic acid in 10mL of deionized water to prepare a 0.05mol / L tannic acid aqueous solution. The pH of the solution is 4.2, which meets the usage standard of 3-5.

[0044] Raw material pretreatment: Take retired lithium iron phosphate positive electrode sheets (aluminum foil current collectors), cut them into 2cm×2cm small pieces, with an initial total mass of 0.1620g.

[0045] Ultrasonic passivation and stripping: The electrode is completely immersed in tannic acid stripping solution, and 25kHz ultrasound is turned on. It is soaked at room temperature for 118s (about 2min). Polyphenols quickly form a passivation film on the aluminum foil surface, and the positive electrode active material automatically falls off the aluminum foil surface.

[0046] Separation, cleaning and drying: Take out the complete aluminum foil, and use vacuum filtration to separate the active powder from the mixed slurry; rinse the aluminum foil and positive electrode powder with water, dry them at 60℃ and weigh them; the total mass of the material after drying is 0.1536g, the mass difference is due to the removal of organic matter from the binder, there is no obvious loss of active metal, and the peeling efficiency is 100%.

[0047] Continuous roll verification: By treating a whole roll of waste positive electrode sheets with the same stripping solution and process conditions, the active material can be completely stripped off, resulting in a complete and undamaged aluminum foil roll (e.g. Figure 3 China A and Figure 3 As shown in Figure B), it possesses industrialized continuous production capabilities.

[0048] The cut negative electrode sheet is completely immersed in a light yellow tannic acid passivation stripping solution for ultrasonic treatment. After the stripping is completed, the whole graphite active material layer and the copper foil without corrosion or damage can be completely separated. The active powder is free of copper shavings, and the copper foil substrate remains flat and bright, which directly proves that the present invention can achieve non-destructive and complete separation of the active material and the current collector.

[0049] Figure 2 These are actual photos comparing the negative electrode sheet before and after peeling in Example 2; Figure 2 Figure A shows the reaction state of the electrode being immersed in a polyphenol complex passivation stripping solution and then subjected to ultrasonic stripping. Figure 2 In Figure B, the product obtained after peeling is shown. The two upper pieces are the completely detached negative electrode graphite active material layers, and the lower piece is the copper foil current collector without damage after peeling. After the reaction, the active material is completely detached from the surface of the copper foil. The complete graphite sheet and the bright, undamaged copper foil are collected separately, with a peeling rate of 100% and no metal debris mixed into the active material, achieving non-destructive separation of the current collector and the active material.

[0050] Example 3 A 0.1 mol / L tea polyphenol aqueous solution was used as the passivation stripping solution, pH=3.8, ultrasonic frequency 30 kHz, and the silicon-carbon negative electrode copper foil was treated by soaking at room temperature for 8 min. After stripping, the copper foil was intact and free from corrosion, and the graphite silicon-carbon powder was free from copper dust. The stripping rate was 100%. The stripping solution can be recycled more than 5 times after pH adjustment and still maintains a stable stripping effect.

[0051] Example 4 A passivation solution of 0.08 mol / L gallic acid and pyrogallol was used to treat the ternary cathode aluminum foil sheet. After immersion in 40 kHz ultrasonic waves at room temperature for 5 min, the active material was completely detached, the aluminum foil remained intact, and the Al impurity content of the powder was 0.031 wt%, which meets the purity requirements for direct regeneration raw materials.

[0052] Mechanical crushing and sorting processes typically involve crushing, screening, air separation, and magnetic separation of retired battery cells or electrode sheets to obtain products such as black powder, copper-aluminum mixtures, diaphragm fragments, and plastic fragments. While these methods have a large processing capacity, they suffer from the following drawbacks: During crushing, aluminum and copper foil fragments can easily enter the black powder, increasing the copper and aluminum impurity content; simultaneously, mechanical impact can damage the particle morphology and crystal structure of active materials, hindering subsequent high-value direct regeneration. Furthermore, mechanical crushing usually requires multi-stage crushing and sorting equipment, resulting in a long process route and significant equipment investment.

[0053] This invention achieves interfacial peeling by adsorption, complexation, or film formation of a polyphenolic hydroxyl complexing passivating agent on the surface of a metal current collector, supplemented by ultrasound. This eliminates the need for mechanical breakage, reduces the entrainment of copper and aluminum foil fragments, and lowers the metal foil impurity content in the black powder. Verification has shown that a 0.05 mol / L tannic acid aqueous solution can achieve complete peeling of the active material layers of the positive and negative electrodes from the current collector within 1-10 minutes at room temperature, with a peeling rate of 100%.

[0054] High-temperature thermal decomposition can remove the active material layer by thermally decomposing binders such as PVDF, CMC, and SBR. However, this method has the following drawbacks: high energy consumption, demanding equipment requirements, and strict requirements for the treatment atmosphere. For fluorinated binder systems, the high-temperature treatment process may also generate fluorinated gases (such as HF), volatile organic compounds, and dust, increasing the burden of exhaust gas treatment. The high-temperature process may also alter the surface structure, lattice defects, residual alkali state, or secondary morphology of the cathode material, thereby affecting the performance of the recycled material.

[0055] This invention avoids high-temperature pyrolysis, employing an aqueous passivation stripping solution operated at room temperature. The process mainly includes contact, stripping, and separation, eliminating the need for complex high-temperature pyrolysis, multi-stage crushing, or strong acid / alkali extraction processes. Based on environmental and economic analysis data, the total energy consumption is only 5.84 MJ / kg of battery, and greenhouse gas emissions are only 0.61 g / kg, far lower than pyrometallurgical, wet, and conventional direct recycling routes. The net profit from processing 1 kg of battery reaches US$9.01, significantly outperforming other recycling methods.

[0056] Strong alkali or strong acid treatment processes can achieve material recovery by dissolving aluminum foil, leaching metal elements, or disrupting interfacial bonding. However, these methods have the following drawbacks: they often do not aim to maintain the integrity of the current collector and the structure of the active material, easily leading to a large influx of metal ions into the liquid phase, increasing the difficulty of subsequent separation, purification, and waste liquid treatment. High-concentration acidic solutions can dissolve some of the active substances, affecting the recovery rate and the quality of the recovered product.

[0057] This invention achieves interfacial exfoliation through the adsorption, complexation, or film formation of a polyphenolic hydroxyl complex passivating agent on the surface of a metal current collector, rather than through the large-scale corrosion or dissolution of aluminum or copper foil by strong acids or alkalis, thus preserving the integrity of the current collector. The amount of transition metals dissolved in the active material is extremely low (Li only 0.21%, Ni 0.27%, Co 0.08%, Mn 0.17%), and the residual Al in the active material after separation is as low as 0.026 wt%.

[0058] Organic solvent swelling or dissolving processes can be effective against binders such as PVDF, but they have the following drawbacks: some organic solvents have issues with toxicity, cost, safety, energy consumption for recycling, and environmental impact; at the same time, the binder composition, compaction density, aging degree, and pore structure of electrodes from different sources vary greatly, resulting in insufficient peeling efficiency and peeling stability when relying solely on solvent action.

[0059] This invention uses a water-based polyphenol solution as the stripping fluid, which is low-cost, safe, and non-toxic. The passivation stripping fluid can be reused, significantly reducing process costs. This invention can be used for both positive and negative electrode sheets; it can be used for retired lithium-ion battery electrodes, as well as for scrap, discarded, and substandard electrodes from lithium battery production processes, making it widely applicable.

[0060] Therefore, this invention employs the aforementioned low-temperature stripping method using polyphenolic hydroxyl complex passivating agents for lithium battery electrode sheets. After stripping, the copper and aluminum foils remain intact without breakage, the crystal structure of the active material is undamaged, and the content of metal impurities in the powder is extremely low. The entire process operates at room temperature, without high temperatures, strong acids or alkalis, or organic solvents. The process flow is concise, the stripping solution is recyclable, and it is green, low-carbon, and cost-effective. This invention is applicable to the resource recycling of retired lithium battery electrode sheets, scrapped electrode sheets from battery production, and offcuts. It can obtain high-purity active powder and intact metal current collectors, and is suitable for subsequent processes such as direct regeneration of battery materials and hydrometallurgy, possessing significant value for large-scale industrial application.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low-temperature stripping method for polyphenol hydroxyl complex passivating agents on lithium battery electrode sheets, characterized in that, Includes the following steps: S1. Provide a lithium battery electrode sheet to be processed. The electrode sheet includes a metal current collector and an active material layer attached to the surface of the metal current collector. The metal current collector is aluminum foil and / or copper foil. S2. Prepare a polyphenol complexing passivation stripping solution, which is an aqueous solution containing a polyphenol hydroxyl complexing passivating agent; S3. Immerse the electrode sheet in the passivation stripping solution; S4. Ultrasonic treatment is applied simultaneously during the infiltration process; S5. Collect the intact metal current collector and the active material powder separately through solid-liquid separation; S6. Post-process the metal current collector and active material powder, and recycle the passivation stripping solution after the pH test meets the standard.

2. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S1, the active material layer is selected from one or more of the following: ternary cathode material, lithium iron phosphate cathode material, lithium cobalt oxide cathode material, lithium manganese oxide cathode material, graphite anode material, and silicon-carbon anode material.

3. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S2, the polyphenol hydroxy complexing passivating agent includes at least one of tannic acid, gallic acid, tea polyphenols, catechins, and pyrogallic acid.

4. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S2, the concentration of the polyphenol hydroxy complex passivating agent in the passivation stripping solution is 0.05–0.1 mol / L, and the pH of the passivation stripping solution is controlled at 3–5.

5. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S3, the contact temperature is 15–60°C; the total contact time is 1–5 min.

6. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S4, the ultrasonic frequency is 20–40 kHz.

7. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S5, the solid-liquid separation method is selected from any one of gravity filtration, vacuum filtration, pressure filtration, centrifugal filtration, membrane filtration, and sedimentation sieving.

8. The low-temperature stripping method for polyphenol hydroxyl complex passivating agent on lithium battery electrode sheets according to claim 1, characterized in that: In step S6, the post-treatment of the metal current collector includes soaking in clean water, rinsing, ultrasonic cleaning, and low-temperature drying; the post-treatment of the active material powder includes washing with water, low-temperature drying, and sieving to remove impurities; the passivation stripping solution can be directly recycled if the pH is maintained in the range of 3 to 5, and can be reused after adding polyphenol passivating agent to adjust the pH if it deviates from the standard range.

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