Method for stripping positive electrode material and aluminum foil of waste lithium battery

Abstract

The invention belongs to the technical field of environmental protection, and provides a method for stripping a waste lithium battery positive electrode material from an aluminum foil, which comprises the following steps: placing a waste lithium battery in air for disassembly to obtain a positive electrode material containing the aluminum foil; cleaning and drying the positive electrode material; putting the dried substance into a citric acid aqueous solution; cleaning the acid-washed substance until no residual acid liquid exists on the surface, and drying until no residual liquid exists on the surface; putting the pole piece containing the acid liquor into a dimethyl sulfoxide or a mixed solvent system of the dimethyl sulfoxide and ethanol until the surface of the pole piece has uniform bulges; and separating the soaked material to obtain the positive electrode material and the aluminum foil. In the acid leaching process, the pole piece fully absorbs acid liquor, and the pole piece can be promoted to absorb an organic solvent and swell by the organic solvent through a micro crack capillary effect when the pole piece is soaked in the organic solvent subsequently. According to the method, the complete aluminum foil is obtained while the positive electrode material is recycled. In the recycling process, waste materials are effectively utilized, and the method is environmentally friendly and has great practical significance.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a method for peeling the positive electrode material of waste lithium batteries from aluminum foil. Background Technology

[0002] Lithium-ion batteries (LIBs) hold a significant share in power supply for portable electronic products, electric vehicles, and energy storage. As LIBs continue to electrify the world, it is estimated that over 1,100 tons of waste will be generated by 2030. However, waste batteries contain many harmful chemicals, such as heavy metals and organic electrolytes, which cannot be disposed of arbitrarily. Furthermore, since my country relies heavily on imports for lithium-ion battery raw materials, the recycling and reuse of waste LIBs is urgently needed. Because the cathode material in spent lithium-ion batteries is mainly bonded to aluminum foil current collectors using binders such as PVDF, and due to the high reactivity of PVDF, it is difficult to ensure complete separation of the aluminum foil and cathode material during the separation process. Collecting the cathode active material from the aluminum foil surface is a crucial step in recycling spent LIBs. To better separate the cathode material from the aluminum foil, the most common industrial method is to directly calcine the electrode sheet at a high temperature of approximately 500℃~600℃ to decompose the binder, polyvinylidene fluoride. This remains the most common and effective method in the industry.

[0003] High-temperature thermal treatment to decompose the organic polyvinylidene fluoride (PVDF) binder in the cathode electrodes of waste lithium-ion batteries offers advantages such as simplicity, convenience, and batch processing, resulting in economies of scale. In industrial production, this method effectively separates the positive electrode active material from the aluminum foil. However, because it involves direct high-temperature calcination to decompose PVDF, while efficient, the high temperatures may damage the positive electrode material. Direct in-situ regeneration of the damaged material may lead to poor regeneration results. Furthermore, the high temperatures reduce the lifespan of production line equipment and result in high energy consumption. Therefore, developing a low-cost, low-energy-consumption, high-efficiency, and environmentally friendly strategy that also protects the positive electrode material to separate the cathode material and aluminum foil is of significant practical importance for the recycling of waste lithium-ion batteries, promoting resource recovery, and protecting the environment.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention was made to solve the above-mentioned problems, and its purpose is to provide a method for separating aluminum foil and positive electrode material by using residual acid inside the electrode sheet, so as to recover the positive electrode material and obtain the complete aluminum foil at the same time.

[0006] This invention provides a method for peeling the positive electrode material of waste lithium batteries from aluminum foil, characterized by the following steps: Step S1: Disassemble the waste lithium battery in air to obtain the positive electrode material containing aluminum foil; Step S2: Clean and dry the positive electrode material containing aluminum foil to obtain the dried material; Step S3: Immerse the dried material in a 0.1M~0.5M citric acid solution at 50℃~60℃ for a first predetermined time to obtain the acid-washed material; Step S4: Clean the acid-washed material until there is no residual acid on the surface and dry it until there is no residual liquid on the surface to obtain the electrode sheet containing acid inside; Step S5: After Step S4 is completed, immediately immerse the electrode sheet containing acid inside in dimethyl sulfoxide or a mixed solvent system of dimethyl sulfoxide and ethanol, and keep it at 50℃~60℃ for a second predetermined time until there is a uniform bulge on the surface of the electrode sheet to obtain the soaked material; Step S6: Separate the soaked material by mechanical force or put it in a vacuum drying oven to dry and separate it to obtain the positive electrode material and aluminum foil.

[0007] The method for separating waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following features: the specific operation of step S2 is as follows: the cathode material containing aluminum foil is washed with anhydrous ethanol 3 to 5 times, then washed with water until the solution is neutral, and vacuum dried at a temperature of 50°C to 70°C for 12 to 24 hours to obtain the dried material.

[0008] The method for peeling the cathode material of waste lithium batteries from aluminum foil provided by the present invention may also have the following features: in step S3, the first predetermined time is 2 to 5 minutes; in step S5, the second predetermined time is 5 to 15 minutes.

[0009] The method for peeling waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following feature: in step S4, the drying method is any one or more of hot air drying, oven drying or natural air drying.

[0010] The method for peeling waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following feature: in step S5, when using a mixed solvent system of dimethyl sulfoxide and ethanol, the volume ratio of dimethyl sulfoxide to ethanol is 9:1 to 7:3.

[0011] The method for separating waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following feature: in step S6, a soft brush or ultrasonic waves are used to separate the soaked material to obtain cathode material and aluminum foil.

[0012] The method for separating waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following features: the specific operation of using ultrasound in step S6 is as follows: the soaked material is placed in double-distilled water for ultrasound to obtain cathode material and aluminum foil.

[0013] The method for separating waste lithium battery cathode material from aluminum foil provided by the present invention may also have the following features: in step S6, when drying and separating the electrode sheet using a vacuum drying oven, the temperature is between 50°C and 70°C, and the drying time is 12h to 24h. After drying, the cathode material and aluminum foil can be separated from the electrode sheet using tweezers.

[0014] The method for separating the cathode material from aluminum foil in waste lithium batteries provided by the present invention may also have the following feature: wherein the cathode material is any one of ternary material, lithium cobalt oxide, or lithium iron phosphate.

[0015] The role and effect of invention This invention provides a method for separating the positive electrode material from aluminum foil in waste lithium batteries. The waste lithium batteries are disassembled in air to obtain the positive electrode material containing aluminum foil. This material is then cleaned and dried. The electrode is then acid-washed with citric acid solution. After acid washing, corrosion occurs at the interface between aluminum and PVDF. Acidic substances and moisture are stored at these corrosion sites, facilitating subsequent infiltration and swelling. The electrode is then infiltrated and swollen using DMSO or a DMSO-ethanol mixture. Comparative experiments show that when the electrode is completely dry (Control Example 1), immersing the acid-washed electrode in DMSO solvent results in only slight bulging at the edges without other noticeable phenomena. We infer that residual moisture is crucial for subsequent swelling. Residual moisture and residual citric acid form an acid film at the interface. During DMSO swelling, the acid film reacts with the aluminum foil to generate gas, creating microcracks in the PVDF phase, increasing the specific surface area, promoting DMSO swelling, and reducing the bond strength between PVDF and aluminum foil. It is worth mentioning that, through a control experiment (i.e., keeping other operations unchanged but omitting step S4, as in Control Example 5), we found that the electrode surface still had bulges, but some areas did not show significant changes. We believe that drying the electrode surface before immersing it in the organic solvent allows for rapid absorption of the organic solvent through the capillary action of the micropores on the electrode surface, enabling rapid diffusion of the organic solvent into the electrode interior. When the black active material layer on the electrode surface bulges (due to swelling caused by DMSO inserting into the PVDF molecular chains), it can be directly peeled off, or the DMSO can be dried in an oven and recovered without affecting the peeling effect. Traditional methods mainly rely on using crushing and heating to soften PVDF and separate aluminum foil and black powder. This method is energy-intensive and easily damages the positive electrode active material (the main component of black powder), while the obtained black powder contains a high amount of aluminum. The method of peeling by immersion in organic solvents usually requires a long time and other conditions, such as ultrasound; especially with DMSO, in our experimental verification, even after immersion at room temperature for a day and a night, the surface black powder did not loosen significantly, as in Control Example 2.

[0016] The acid used in this invention is an organic acid that can complex with aluminum ions and is non-volatile. Citric acid is preferred. This invention uses a 0.1~0.5M citric acid solution, with a laboratory-measured pH range of 1.88~2.23. This weak acidity means that the acid resistance requirements for equipment are relatively low in actual industrial production, significantly reducing equipment maintenance and corrosion prevention costs.

[0017] In this invention, the reaction temperature is maintained below 60°C throughout, resulting in a highly crystalline NCM ternary material, demonstrating extremely high structure retention of the active material. Direct ICP-OES characterization of the obtained black powder revealed an aluminum content of only 0.26%. ICP-OES characterization of the solution after acid etching at 0.5M concentration and the solution after permeation and swelling of DMSO showed that the aluminum foil mass loss accounted for approximately 0.165% of the electrode mass, indicating an extremely low aluminum loss rate. Direct digestion of the stripped aluminum foil, and analysis of the residual nickel, cobalt, manganese, and lithium elements on the foil, revealed a stripping efficiency exceeding 99.5%. Attached Figure Description

[0018] Figure 1 These are photographs of waste lithium battery electrodes after acid soaking and DMSO swelling in Embodiment 1 of the present invention. Figure 2 This is a photograph of aluminum foil after the surface active material of the waste lithium battery electrode sheet has been brushed off with a brush in Embodiment 1 of the present invention; Figure 3 This is the X-ray diffraction pattern in Embodiment 1 of the present invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following describes in detail a method for peeling off waste lithium battery cathode material from aluminum foil, in conjunction with embodiments and accompanying drawings.

[0020] Unless otherwise specified, the raw materials and reagents used in the following examples can be purchased from conventional commercial channels.

[0021] The method for peeling the cathode material from aluminum foil in waste lithium batteries provided by this invention specifically includes the following steps: Step S1: Disassemble the waste lithium battery in air to obtain the positive electrode material containing aluminum foil. The positive electrode material is a ternary material (NCM), lithium cobalt oxide (LCO), or lithium iron phosphate (LFP).

[0022] Step S2 involves cleaning and drying the positive electrode material containing aluminum foil to obtain the dried material. The specific operation of this step is as follows: The positive electrode material containing aluminum foil is washed with anhydrous ethanol 3 to 5 times, then washed with water until the solution is neutral, and then vacuum dried at 50℃ to 70℃ for 12 to 24 hours to obtain the dried material, i.e., the dried electrode sheet.

[0023] Step S3: Cut the dried electrode sheet into any size and place it in a citric acid aqueous solution (0.1M~0.5M). Keep it at a water bath temperature of 50℃~60℃ for 5 minutes to obtain the acid-leached material.

[0024] The Leici PHB-4 pH meter measured the pH of a 0.1M citric acid solution kept in a 25℃ water bath to be 2.23; and the pH of a 0.5M citric acid solution kept in a 25℃ water bath to be 1.88.

[0025] Step S4: After acid soaking in the previous step, wash the material twice with double-distilled water, then rinse once with ethanol to ensure no residual acid remains on the surface. Then dry it using a hair dryer or by air drying until no residual liquid remains on the electrode surface. This step is mainly to remove the solution from the micropores on the electrode surface to reduce the resistance to subsequent DMSO entry into the electrode, while ensuring that there is residual acid and moisture at the interface between the electrode active material and the aluminum foil. In step S5, the electrode sheet after the above treatment is immediately placed in dimethyl sulfoxide (DMSO) or a mixed solvent of DMSO and ethanol and kept at 50°C to 60°C for 10 minutes to obtain the soaked electrode sheet. When using a mixed solvent of DMSO and ethanol, the volume ratio of DMSO to ethanol is preferably controlled between 9:1 and 3:7. The word "immediately" in step S5 of this invention does not have a specific time limit and is understood by those skilled in the art as "immediately" in experimental operation scenarios. When step S4 is completed and step S5 is about to proceed, the electrode sheet surface is dry and contains acid inside.

[0026] Step S6: After soaking, the electrode can be separated using weak mechanical force. Alternatively, the soaked electrode can be placed in a vacuum drying oven, dried, and then the aluminum foil and positive electrode material can be separated using tweezers. DMSO can be recovered simultaneously with the positive electrode material (black powder) and aluminum foil.

[0027] In this invention, the cleaning solution is double-distilled water.

[0028] <Example 1> A method for separating waste lithium battery cathode material from aluminum foil specifically includes the following steps: Step S1: Place the waste lithium battery in the air and disassemble it with a disassembly machine. Classify the disassembled materials according to their material composition to obtain the positive electrode material containing aluminum foil. Step S2: Rinse with double-distilled water until neutral, and vacuum dry at 50°C for 12 hours.

[0029] Step S3: Cut the electrode sheet into approximately 2cm x 2cm pieces, place them in 10ml of 0.5M citric acid solution, and incubate at 60°C for 3 minutes. Step S4: Rinse the electrode sheets obtained after acid leaching with double-distilled water and anhydrous ethanol in sequence. Dry the electrode sheets using a hairdryer on hot air mode, stopping drying immediately when the residual ethanol on the electrode sheet surface is just dried. "Just dried" means stopping the hairdryer the moment the residual liquid on the surface is visibly observed to disappear completely.

[0030] Step S5: Immediately place the surface-dried electrode into 10ml of pure DMSO solvent and keep it at 60℃ for 10min.

[0031] Step S6: Remove the electrode. You will observe bulges on the electrode surface, indicating swelling. Gently brush away the black powder from the surface of the electrode with a soft brush to collect the high-purity black powder and aluminum foil. This black powder is the positive electrode material.

[0032] The aluminum content of the CA (citric acid) solution (10 ml) obtained in step S3 and the DMSO solution (10 ml) obtained in step S5 was determined using an Agilent ICP OES730. By multiplying the aluminum concentration in the solution by the solution volume, we found that the aluminum leaching from the citric acid solution obtained in step S3 accounted for only 1.59% of the total aluminum foil weight and 0.165% of the total electrode weight; while the aluminum leaching from the DMSO was negligible. This demonstrates that this method can separate the aluminum foil and the positive electrode material without severely corroding the aluminum foil.

[0033] Samples of the stripped electrode sheets and black powder were taken separately and each sample was added to 5 ml of nitric acid, 1 ml of hydrofluoric acid, 1 ml of hydrogen peroxide, and 1 ml of hydrochloric acid, respectively, and heated in a 180°C oven for 8 hours for digestion. The residual nickel, cobalt, manganese, and lithium elements in the electrode digestion solution were determined using ICP-OES, and the aluminum content in the digested black powder was measured. The purpose of this method was to determine the residual nickel, cobalt, manganese, and lithium elements on the surface of the stripped electrode sheets, and the aluminum content in the black powder of the stripped NCM. The aluminum foil was digested and ICP-OES was used to determine the residual nickel, cobalt, manganese, and lithium elements on the aluminum foil surface to assess the mass fraction of residual battery material. The black powder was digested and its aluminum content was measured to determine whether a large amount of aluminum impurities were introduced into the black powder after stripping. Tests showed that the stripping efficiency was extremely high, with only 0.371% wt of surface active material remaining, a stripping efficiency exceeding 99.5%, and the aluminum content in the black powder was only 0.26%. This demonstrates that during the acid leaching process, the aluminum ions displaced by hydrogen ions are complexed by citrate ions, preventing them from penetrating the black powder material.

[0034] Figure 1 These are camera photographs taken of the waste lithium battery electrodes from Embodiment 1 of this invention after acid immersion and DMSO swelling. It can be observed that after the above process, bulges appear on the electrode surface, indicating that the PVDF in the active material layer on the electrode surface has swollen with DMSO. At this point, the bonding force between the electrode and PVDF is extremely weak, and they can be separated using methods such as ultrasound or stirring. However, considering cost and the integrity of the aluminum foil, this solution recommends using a soft brush to separate the positive electrode material and the aluminum foil.

[0035] Figure 2This is a photograph taken with a camera of the aluminum foil after the waste lithium battery electrodes in Embodiment 1 of the present invention have been soaked in acid and swollen with DMSO, and then separated with a brush. It can be seen that the surface of the aluminum foil is intact and there is no large amount of active material residue.

[0036] Figure 3 This is the X-ray diffraction pattern in Embodiment 1 of the present invention.

[0037] Phytic acid passivation and stripping is a proven method for separating the cathode material and aluminum foil without damaging the cathode material structure. We compared this method with NCM material obtained by directly using phytic acid (PA NCM) passivation and stripping (Comparative Example 3). In the figure, CA+DMSO NCM represents the black powder obtained in Example 1, and PA NCM represents the black powder obtained in Comparative Example 3. Figure 3 It can be seen that, compared with the black powder obtained by phytic acid passivation exfoliation, the characteristic peaks of the black powder obtained by the CA+DMSO exfoliation method are completely preserved. This proves that the method does not damage the structural stability of the material. At the same time, the absence of obvious impurity peaks also indirectly confirms that the black powder obtained by the method has high purity.

[0038] <Example 2> A method for separating waste lithium battery cathode material from aluminum foil specifically includes the following steps: Step S1: Place the waste lithium battery in the air and disassemble it with a disassembly machine. Classify the disassembled materials according to their material composition to obtain the positive electrode material containing aluminum foil. Step S2: Rinse with cleaning solution until neutral, and vacuum dry at 60°C for 24 hours.

[0039] Step S3: Cut the electrode into approximately 2cm*2cm pieces, place them in 10ml of 0.125M citric acid solution, and incubate at 60 degrees Celsius for 3 minutes.

[0040] Step S4: Rinse the electrode obtained after acid leaching with double-distilled water and anhydrous ethanol in sequence. Allow the ethanol on the electrode surface to evaporate at room temperature. Proceed to the next step immediately when the residual ethanol on the electrode surface is just dried.

[0041] Step S5: Immediately place the surface-dried electrode into 10 ml of solvent with DMSO:ethanol = 7:3 and keep it at 60°C for 10 min.

[0042] Step S6: Remove the electrode. A bulge can be observed on the electrode surface, indicating swelling. Dry the electrode in a 60℃ oven for 12 hours. Once removed, the electrode surface is flat again, indicating that DMSO has been completely removed from the electrode. However, the black powder can still be removed whole from the aluminum foil surface using tweezers.

[0043] <Comparison with Example 1> In this comparative example, the product was thoroughly dried after acid leaching, and then swelled using an organic solvent. The specific process is as follows: Used lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. The positive electrode material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 18 hours. The dried positive electrode material containing aluminum foil was cut into 1cm x 1cm pieces. These pieces were then placed in 10ml of 0.5M citric acid solution and kept at 60°C for 5 minutes. They were then dried using a hairdryer, and hot air was continued for 1 minute on each side to completely remove moisture. The dried electrode sheets were then placed in 10ml of pure DMSO solvent and kept at 60°C for 30 minutes. Except for slight bulging at the edges, there were no significant changes inside the electrode sheets.

[0044] By comparing Example 2 and Comparative Example 1, it is demonstrated that the residual acid at the interface between the active material layer of the electrode and the aluminum foil can synergistically generate gas when swelled using an organic solvent. This gas at the interface creates micro-cracks in the active material layer, promoting the swelling of PVDF by DMSO. This demonstrates the practical effectiveness of the proposed method.

[0045] <Comparison with Example 2> This comparative example only uses DMSO to soak the electrode sheet. The specific process is as follows: Used lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. This material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 24 hours. The dried positive electrode material containing aluminum foil was cut into 1cm x 1cm pieces. These pieces were then immersed in 10ml of pure DMSO solvent at room temperature for 24 hours, with no significant effect observed. This demonstrates the practical effectiveness of the proposed method.

[0046] <Comparison with Example 3> This comparative example uses phytic acid solution to soak the electrode sheets to achieve peeling. The specific process is as follows: Waste lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. The positive electrode material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 24 hours. Phytic acid was prepared into a 30 wt% aqueous solution. 5 ml of the phytic acid solution was taken, and the dried positive electrode material containing aluminum foil, cut into 1 cm x 1 cm pieces, was added to the solution. The aluminum foil and active material were observed to separate within 10 minutes. The active material was collected by vacuum filtration, washed with double-distilled water until neutral, and then dried in an oven at 60°C for 24 hours.

[0047] <Comparison with Example 4> In the control example, a 5M acetic acid aqueous solution was used instead of a citric acid aqueous solution to acid wash the electrode sheets, with all other operations remaining unchanged. The specific process is as follows: Waste lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. The positive electrode material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 24 hours. The dried positive electrode material containing aluminum foil was cut into 1cm x 1cm pieces. These pieces were then acid-washed for 5 minutes in a 5M acetic acid solution (pH value around 2.5, as determined by pH testing). The acid-washed electrode sheets were then cleaned successively with double-distilled water and anhydrous ethanol, and their surfaces were dried with a hair dryer. The dried electrode sheets were immediately immersed in 10ml of pure DMSO solvent for 20 minutes; no significant changes were observed on the electrode surface. During the drying process, most of the acetic acid evaporated, resulting in insufficient acid concentration at the interface. Therefore, citric acid is preferred in this method.

[0048] <Comparison with Example 5> This comparative example omits the drying step; the specific process is as follows: Used lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. The material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 24 hours. The dried positive electrode material containing aluminum foil was cut into 2cm x 2cm pieces. The electrode sheets were immersed in 10ml of 0.5M citric acid solution and kept at that temperature for 3 minutes. Then, the electrode sheets were rinsed sequentially with double-distilled water and anhydrous ethanol to remove residual acid from the surface. Finally, they were directly immersed in 10ml of DMSO solvent and kept at 60°C for 15 minutes. Most areas bulged, while the central area showed no significant change.

[0049] By comparing Example 1 above with this comparative example, we found that when the pickling is completed and the product is ready to be put into an organic solvent, it is best to dry the surface residue of anhydrous ethanol, which can reduce the resistance of DMSO to diffusion into the interior.

[0050] <Comparison with Example 6> This comparative example uses ethanol instead of DMSO solvent, and the specific process is as follows: Used lithium batteries were placed in air and disassembled using a disassembly machine. The disassembled materials were classified according to their composition, and the positive electrode material containing aluminum foil was obtained. The positive electrode material was rinsed with double-distilled water until neutral and then vacuum-dried at 60°C for 19 hours. The dried positive electrode material containing aluminum foil was cut into 2cm x 2cm pieces. The electrode sheets were immersed in 10ml of 0.25M citric acid solution for 3 minutes, then rinsed successively with double-distilled water and anhydrous ethanol. The sheets were then dried with a hair dryer until just dry, and finally immersed directly in 10ml of ethanol solvent at 60°C for 30 minutes.

[0051] Experiments showed that most areas of the electrode remained unchanged.

[0052] <Example 3> A method for separating waste lithium battery cathode material from aluminum foil specifically includes the following steps: Step S1: Place the waste lithium battery in the air and disassemble it with a disassembly machine. Classify the disassembled materials according to their material composition to obtain the positive electrode material containing aluminum foil. Step S2: Rinse with cleaning solution until neutral, and vacuum dry at 70°C for 18 hours.

[0053] Step S3: Cut the electrode into approximately 2cm*2cm pieces, place them in 10ml of 0.1M citric acid solution, and incubate at 60 degrees Celsius for 3 minutes.

[0054] Step S4: Rinse the electrode obtained after acid leaching with double-distilled water and anhydrous ethanol in sequence. Allow the ethanol on the electrode surface to evaporate at room temperature. Proceed to the next step immediately when the residual ethanol on the electrode surface is just dried.

[0055] Step S5: Immediately place the surface-dried electrode into 10 ml of pure DMSO solvent and keep it at 60°C for 10 min.

[0056] Step S6: Remove the electrode. You will observe bulges on the electrode surface, indicating swelling. Then, simply use a brush to separate the black powder and aluminum foil from the electrode surface. <Example 4> A method for separating waste lithium battery cathode material from aluminum foil specifically includes the following steps: Step S1: Place the waste lithium battery in the air and disassemble it with a disassembly machine. Classify the disassembled materials according to their material composition to obtain the positive electrode material containing aluminum foil. Step S2: Rinse with cleaning solution until neutral, and vacuum dry at 50°C for 24 hours.

[0057] Step S3: Cut the electrode into approximately 2cm*2cm pieces, place them in 10ml of 0.25M citric acid solution, and incubate at 60 degrees Celsius for 4 minutes.

[0058] Step S4: Rinse the electrode obtained after acid leaching with double-distilled water and anhydrous ethanol in sequence. Dry it with a hair dryer until the surface is just dry.

[0059] Step S5: Immediately place the surface-dried electrode into 5 ml of a solvent of DMSO:ethanol = 9:1 and keep it at 60°C for 5 min.

[0060] Step S6: Remove the electrode. You can observe bulges on the surface of the electrode, which indicates that the electrode has swollen. Then, simply use a brush to separate the black powder and aluminum foil from the surface of the electrode.

[0061] The role and effect of the embodiments The method for separating the positive electrode material from aluminum foil in waste lithium batteries according to embodiments of the present invention involves disassembling the waste lithium batteries in air to obtain positive electrode material containing aluminum foil; then cleaning and drying the obtained positive electrode material containing aluminum foil; and then using low-concentration citric acid at a low temperature to open the micropores on the electrode surface. Simultaneously, the citric acid produces micro-chemical etching at the interface between the aluminum foil and PVDF, leaving residual acidic substances and moisture at the etched areas. Subsequent swelling with a swelling agent is then carried out simultaneously, with the acid corroding the aluminum foil and generating gas in a synergistic process: the gas generated by the acid creates micro-cracks in the active material layer, promoting the contact, penetration, and swelling of DMSO. Controlling the drying process to surface dryness while leaving residual moisture internally is crucial because if only dry citric acid crystals exist inside the electrode, micro-corrosion cannot occur at the interface; however, if the surface is moist, the driving force for subsequent organic solvent penetration is solute / solvent interdiffusion, whereas when the surface is dry, solvent can be directly absorbed through capillary action, resulting in faster organic solvent penetration. These mechanisms work synergistically to achieve ultra-fast swelling within 15 minutes, which is impossible with a single solvent.

[0062] The acid leaching process is primarily to allow the electrode to fully absorb the acid solution. During subsequent organic solvent penetration and immersion, residual acidic solutes and moisture corrode the aluminum foil, generating hydrogen gas. This creates micro-cracks in the active material layer of the electrode. When immersing in organic solvents later, the capillary effect of these micro-cracks promotes the electrode's absorption and swelling of the solvent. This method recovers the positive electrode material while also obtaining intact aluminum foil.

[0063] The embodiments of this invention utilize a low-cost, low-energy-consumption, high-efficiency, and environmentally friendly strategy to separate cathode materials and aluminum foil, enabling safe and simple recycling of spent lithium batteries. The recycling process effectively utilizes waste materials while being environmentally friendly, and has significant practical implications for the recycling of spent lithium batteries, promoting resource recovery, and protecting the environment. Compared to existing spent lithium battery recycling technologies, this method is simple, direct, and green, performing the stripping process at lower temperatures while achieving environmental benefits.

[0064] Furthermore, weak acids and DMSO solvents are used throughout the process. DMSO solvent has relatively low toxicity, a high evaporation temperature, and is environmentally friendly and safe. We use 0.1~0.5M citric acid solution, with a pH range of 1.88~2.23 measured in the laboratory. The acidity is relatively weak, and the requirements for the acid resistance of equipment are relatively low in actual industrial production.

[0065] In addition, we used a solvent mixture of ethanol and DMSO to reduce the absorption of DMSO by the electrode and thus reduce costs. However, through this implementation case, we can also see that the DMSO we use has a very low dependence on purity, and even recycled DMSO can be used for stripping.

[0066] In addition, the double-distilled water used in the stripping process does not participate in the reaction and can be reused multiple times, and the citric acid from the acid washing step can be reused.

[0067] Furthermore, our DMSO does not participate in any chemical reaction throughout the process. In the DMSO impregnation step, only the physical change of DMSO swelling PVDF occurs. We compared the electrode weight before and after impregnation with the DMSO-ethanol swelling agent and found that after impregnation with 0.1M acid for five minutes, followed by impregnation with a 7:3 (DMSO:ethanol) solution for ten minutes, the surface bulged. After wiping away the residual solvent with lint-free paper, the electrode weight increased by 28%, meaning the electrode only absorbed 28% of its own weight in DMSO. Moreover, residual DMSO remains on the surface of the swollen electrode. Direct heating accelerates evaporation, and the vapor is then recovered. Therefore, DMSO can be recovered from the swollen electrode using a vacuum drying oven, similar to how NMP is recovered through drying in power battery production lines, further reducing costs.

[0068] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for peeling the positive electrode material of waste lithium batteries from aluminum foil, characterized in that, Includes the following steps: Step S1: Disassemble the waste lithium battery in the air to obtain positive electrode material containing aluminum foil; Step S2: The positive electrode material containing aluminum foil is cleaned and dried to obtain the dried material; Step S3: Immerse the dried material in a 0.1M to 0.5M citric acid solution at 50℃ to 60℃ for a first predetermined time to obtain the acid-washed material. Step S4: The acid-washed material is cleaned until there is no residual acid on the surface and dried until there is no residual liquid on the surface to obtain an electrode containing acid inside. After step S5 and step S4 are completed, the electrode containing the acid solution is immediately immersed in dimethyl sulfoxide or a mixed solvent system of dimethyl sulfoxide and ethanol, and kept at 50°C to 60°C for a second predetermined time until the surface of the electrode has uniform bulges, thus obtaining the soaking material. Step S6: Separate the soaked material by mechanical force or dry it in a vacuum drying oven to obtain the positive electrode material and aluminum foil.

2. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, The specific operation of step S2 is as follows: the positive electrode material containing aluminum foil is washed with anhydrous ethanol 3 to 5 times, then washed with water until the solution is neutral, and then vacuum dried at a temperature of 50℃ to 70℃ for 12h to 24h to obtain the dried material.

3. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, In step S3, the first predetermined time is 3 to 5 minutes; in step S5, the second predetermined time is 5 to 15 minutes.

4. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, In step S4, the drying method is any one or more of hot air drying, oven drying, or natural air drying.

5. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, In step S5, when using a mixed solvent system of dimethyl sulfoxide and ethanol, the volume ratio of dimethyl sulfoxide to ethanol is 9:1 to 7:

3.

6. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, In step S6, the soaking material is separated using a soft brush or ultrasound to obtain the positive electrode material and the aluminum foil.

7. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 6, characterized in that: in, The specific operation of using ultrasound in step S6 is as follows: the soaking material is immersed in double-distilled water and ultrasonically sonicated to obtain the positive electrode material and the aluminum foil.

8. The method for peeling the cathode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, In step S6, when drying and separating the electrode sheets using a vacuum drying oven, the temperature is between 50℃ and 70℃, and the drying time is 12h to 24h. After drying, the positive electrode material and aluminum foil can be separated using tweezers.

9. The method for peeling the positive electrode material of waste lithium batteries from aluminum foil according to claim 1, characterized in that: in, The cathode material is any one of ternary materials, lithium cobalt oxide, or lithium iron phosphate.

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