A method for recovering aluminum foil and boehmite from lithium-ion batteries

Abstract

This application relates to a method for recovering aluminum foil and boehmite from lithium-ion batteries. The method includes: obtaining a current collector aluminum foil with an insulating coating from the lithium-ion battery; heat-treating the current collector aluminum foil to decompose the insulating coating, obtaining a material; mixing the material with a solution containing additives, followed by ultrasonic treatment to decompose any remaining insulating coating and completely separate the insulating coating from the aluminum foil, obtaining aluminum foil and a solution containing high-purity boehmite. This application solves the technical problem of the difficulty in effectively separating the insulating coating from the current collector in existing lithium-ion batteries.

Description

Technical Field

[0001] This application relates to the field of waste battery material recycling technology, and in particular to a method for recovering aluminum foil and boehmite from lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, with their high energy density, light weight, and high safety, are widely used in electronic devices, electric vehicles, and industrial energy storage. With the rapid growth in the production and use of lithium-ion batteries, the number of waste lithium-ion batteries is also increasing dramatically. These waste lithium-ion batteries contain a large amount of non-renewable and economically valuable metal resources, such as aluminum or copper foil used as current collectors, electrode powder, and coating materials like boehmite. Therefore, the effective recycling of waste lithium-ion batteries is crucial for alleviating resource pressure and achieving sustainable development in the lithium-ion battery industry.

[0003] Lithium-ion batteries commonly use multi-tab wound positive electrode sheets. An insulating material is coated on the empty foil area near the tabs as a safety zone to prevent contact between the positive electrode tab empty foil area and the negative electrode sheet after winding or stacking, thus providing insulation. However, during the recycling of existing electrode sheets, it has been found that the insulating layer located at the edge of the current collector is difficult to peel off from the current collector, making it difficult to fully and efficiently recycle the current collector, resulting in a low recovery rate of the electrode sheets. Therefore, how to effectively separate the insulating layer from the current collector, thereby efficiently recycling both the insulating coating and the current collector, is an urgent problem to be solved. Summary of the Invention

[0004] This application provides a method for recovering aluminum foil and boehmite from lithium-ion batteries, thereby solving the existing technical problem of the difficulty in effectively separating the insulating coating from the current collector in lithium-ion batteries.

[0005] In a first aspect, this application provides a method for recovering aluminum foil and boehmite from lithium-ion batteries, the method comprising:

[0006] A current collector aluminum foil with an insulating coating is obtained for use in lithium-ion batteries;

[0007] The current collector aluminum foil is heat-treated to decompose the insulating coating and obtain the material.

[0008] The material is mixed with a solution containing additives and then subjected to ultrasonic treatment to decompose the residual insulating coating and completely separate the insulating coating from the aluminum foil, resulting in aluminum foil and a solution containing high-purity boehmite.

[0009] Optionally, the process parameters for the heat treatment include: temperature 290℃~480℃, time 10min~150min.

[0010] Optionally, the process parameters for the ultrasonic treatment include:

[0011] Power 5W~60W, frequency 20kHz~40kHz, time 1s~30s.

[0012] Optionally, the additive includes at least one of the following: alcohols, surfactants, and amino acids.

[0013] Optionally, the alcohols include at least one of the following: ethanol and methanol.

[0014] Optionally, the surfactant includes at least one of the following: sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

[0015] Optionally, the amino acid class includes at least one of the following: glycine, alanine, valine, leucine, glutamic acid, and lysine.

[0016] Optionally, the additive is 0.001 to 0.01 parts by weight relative to 1000 parts by weight of the material.

[0017] Optionally, the insulating coating may include polyvinylidene fluoride as a component.

[0018] Optionally, the process of mixing the material with a solution containing additives and then subjecting it to ultrasonic treatment to decompose the residual insulating coating, thereby obtaining aluminum foil and a solution containing high-purity boehmite, further includes:

[0019] The solution containing high-purity boehmite was filtered to obtain filtrate and high-purity boehmite wet cake.

[0020] The high-purity boehmite wet cake is dried to obtain high-purity boehmite;

[0021] The aluminum foil was washed with the filtrate to obtain high-purity aluminum foil;

[0022] The filtrate after washing the aluminum foil is returned to the ultrasonic treatment to achieve the recycling of the filtrate.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art:

[0024] The method for recovering aluminum foil and boehmite from lithium-ion batteries provided in this application involves heat-treating the current collector aluminum foil with an insulating coating. This heat treatment decomposes the insulating coating adhesive with low energy consumption. Then, with the aid of additives, the heat-treated material is further processed using ultrasound. This process further dissolves the residual coating adhesive and completely separates the insulating coating from the aluminum foil without damaging the aluminum foil due to the high intensity and duration of ultrasound, ensuring the recovery of high-purity boehmite and aluminum foil. Therefore, this method achieves efficient separation and high-value recycling of lithium-ion battery current collector aluminum foil with an insulating coating under low energy consumption and a shorter process flow. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic flowchart illustrating a method for recovering aluminum foil and boehmite from lithium-ion batteries, provided in an embodiment of this application.

[0028] Figure 2 An XRD pattern of high-purity boehmite provided for an embodiment of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0031] In this application, and in the description of this specification, the terms "comprising," "including," etc., mean "including but not limited to." In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0033] Figure 1 A schematic flowchart illustrating a method for recovering aluminum foil and boehmite from lithium-ion batteries, provided in this application embodiment; please refer to [link / reference]. Figure 1 This application provides a method for recovering aluminum foil and boehmite from lithium-ion batteries, the method comprising:

[0034] S1. Obtain a current collector aluminum foil with an insulating coating for use in lithium-ion batteries;

[0035] In some embodiments, the insulating coating comprises polyvinylidene fluoride.

[0036] In this embodiment of the application, the current collector aluminum foil with an insulating coating in the lithium-ion battery is the empty foil area of ​​the positive electrode sheet of the lithium battery with an insulating coating, and the composition of the insulating coating may include polyvinylidene fluoride.

[0037] S2. The current collector aluminum foil is heat-treated to decompose the insulating coating and obtain the material;

[0038] In some embodiments, the process parameters of the heat treatment include: temperature 290℃~480℃, time

[0039] 10 min to 150 min.

[0040] In this embodiment, the current collector aluminum foil with an insulating coating is directly subjected to heat treatment at a lower temperature and for a shorter time, which can achieve the decomposition of the insulating coating adhesive with low energy consumption. Within the aforementioned heat treatment temperature and time ranges, the separation of the coating from the aluminum foil is promoted to be thorough, improving the boehmite recovery rate and aluminum foil purity, while avoiding the decomposition of boehmite in the coating. This avoids excessive adhesive residue in the coating and alleviates the pressure of subsequent weak ultrasonic treatment to decompose the adhesive. For example, the aforementioned temperatures can be 290℃, 300℃, 310℃, 320℃, 330℃, 350℃, 370℃, 390℃, 410℃, 430℃, 450℃, 480℃, etc., and the aforementioned times can be 10min, 20min, 30min, 40min, 50min, 60min, 70min, 90min, 110min, 130min, 150min, etc.

[0041] S3. The material is mixed with a solution containing additives and then subjected to ultrasonic treatment to decompose the residual insulating coating and completely separate the insulating coating from the aluminum foil, thereby obtaining aluminum foil and a solution containing high-purity boehmite.

[0042] In some embodiments, the process parameters of the ultrasonic treatment include:

[0043] Power 5W~60W, frequency 20kHz~40kHz, duration 1s~30s.

[0044] In this embodiment, under the action of the ultrasonic treatment additive, and combined with the use of weak ultrasound to perform a short-term ultrasonic treatment on the heat-treated material, the residual coating adhesive after heat treatment is further dissolved and separated without damaging the aluminum foil due to high ultrasonic intensity and long duration, thus ensuring the recovery of high-purity boehmite and aluminum foil. Using the ultrasonic intensity, frequency, and processing time within the aforementioned range protects the surface of the current collector aluminum foil, preventing unevenness caused by ultrasonic waves and reducing the risk of foil breakage. This ensures effective separation of the adhesive on the insulating layer, protects the integrity of the aluminum foil, and ultimately guarantees the purity and recovery rate of the recovered boehmite. For example, the power can be 5W, 10W, 15W, 20W, 25W, 30W, 40W, 50W, 60W, etc., the frequency can be 20kHz, 25kHz, 30kHz, 35kHz, 40kHz, etc., and the time can be 1s, 2s, 3s, 4s, 5s, 10s, 15s, 20s, 25s, 30s, etc.

[0045] In some embodiments, the additive includes at least one of the following: alcohols, surfactants, and amino acids.

[0046] In some embodiments, the alcohols include at least one of the following: ethanol and methanol.

[0047] In some embodiments, the surfactant includes at least one of the following: sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0048] In some embodiments, the amino acid class includes at least one of the following: glycine, alanine, valine, leucine, glutamic acid, and lysine.

[0049] In this embodiment, the above-mentioned materials are mixed with a solution containing additives for the aforementioned ultrasonic treatment. The solution containing additives can be prepared with water, which serves to uniformly disperse the additives and materials. Water is a clean energy source and will not chemically react with the additives and materials. The additives react with the adhesive on the insulating coating of the material surface due to the principle of like dissolves like, and can activate the surface of the insulating coating to promote the decomposition of any remaining insulating coating. Exemplarily, alcohols, surfactants, and amino acid additives can be used. Alcohols can be ethanol or methanol, surfactants can be sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, and amino acids can be glycine, alanine, valine, leucine, glutamic acid, or lysine.

[0050] In some embodiments, the additive is 0.001 to 0.01 parts by weight relative to 1000 parts by weight of the material.

[0051] In this embodiment, the dosage of the above-mentioned additive is limited to promote the separation of the coating from the aluminum foil, ensure complete decomposition of the coating adhesive, and without affecting the purity, recovery rate, and aluminum foil purity of the boehmite. Generally, the dosage of the additive is calculated relative to the material after heat treatment and cooling to room temperature. For example, relative to 1000 parts by weight of the material, the above-mentioned additive can be 0.001 parts by weight, 0.002 parts by weight, 0.003 parts by weight, 0.004 parts by weight, 0.005 parts by weight, 0.006 parts by weight, 0.007 parts by weight, 0.008 parts by weight, 0.009 parts by weight, 0.01 parts by weight, etc.

[0052] In some embodiments, the process of mixing the material with a solution containing additives, followed by ultrasonic treatment to decompose the residual insulating coating, yielding aluminum foil and a solution containing high-purity boehmite, further includes:

[0053] S4. Filter the solution containing high-purity boehmite to obtain filtrate and high-purity boehmite wet cake.

[0054] The high-purity boehmite wet cake is dried to obtain high-purity boehmite;

[0055] S5. Wash the aluminum foil with the filtrate to obtain high-purity aluminum foil;

[0056] The filtrate after washing the aluminum foil is returned to the ultrasonic treatment to achieve the recycling of the filtrate.

[0057] In this embodiment, after the ultrasonic treatment, the aluminum foil is retrieved, and the solution containing high-purity boehmite is filtered to obtain filtrate and a high-purity boehmite wet cake. The high-purity boehmite wet cake is dried at ≤105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The retrieved aluminum foil is washed clean with the filtrate to obtain high-purity aluminum foil, and the washing solution is recycled into the ultrasonic treatment process. The recovered high-purity boehmite is mainly composed of boehmite, with a mass fraction greater than 99.9%, and contains trace amounts of Si, Fe, Na, and Ca impurities. It can be reused as a raw material for the positive electrode insulating coating of lithium batteries. Figure 2 For an XRD pattern of high-purity boehmite provided in this application embodiment, please refer to [link to XRD pattern]. Figure 2 This indicates fewer impurity peaks and higher purity. The recovered high-purity aluminum foil is mainly composed of aluminum, with a mass fraction greater than 99.8%, and contains trace amounts of Si, Fe, and Cu impurities. It can be recycled as a raw material for battery-grade aluminum foil.

[0058] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0059] Example 1

[0060] Weigh out the empty foil area of ​​the positive electrode of a lithium battery with an insulating coating, i.e., the current collector aluminum foil with an insulating coating. Heat-treat at 290℃ for 150 min, cool to room temperature, and then place it in deionized water containing 0.01‰ of the total weight of the heat-treated and cooled materials in a mixture of ethanol and sodium dodecyl sulfate (mass ratio 1:2). Ultrasonically treat for 15 s at an ultrasonic intensity of 30 W and a frequency of 25 kHz. Remove the aluminum foil, filter the ultrasonically treated aqueous solution, and dry the filter cake at 105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The removed aluminum foil is washed clean with the filtrate to obtain high-purity aluminum foil. The washing solution is recycled into the ultrasonic treatment process.

[0061] Example 2

[0062] Weigh out the empty foil area of ​​the positive electrode of a lithium battery with an insulating coating, i.e., the current collector aluminum foil with an insulating coating. Heat-treat at 480℃ for 10 minutes, cool to room temperature, and then place it in deionized water containing 0.001‰ of the total weight of the materials after heat treatment and cooling to room temperature, a mixture of sodium dodecylbenzenesulfonate, glycine, and alanine (mass ratio 1:2:3). Ultrasonically treat for 1 second at an ultrasonic intensity of 5W and a frequency of 20kHz. Remove the aluminum foil, filter the ultrasonically treated aqueous solution, and dry the filter cake at 105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The removed aluminum foil is washed clean with the filtrate to obtain high-purity aluminum foil. The washing solution is recycled into the ultrasonic treatment process.

[0063] Example 3

[0064] Weigh out the empty foil area of ​​the positive electrode of a lithium battery with an insulating coating, i.e., the current collector aluminum foil with an insulating coating. Heat-treat at 450℃ for 120 minutes, cool to room temperature, and then put it into deionized water containing 0.002‰ of the total weight of the heat-treated and cooled materials in a mixture of ethanol and alanine (mass ratio 10:1). Ultrasonically treat for 30 seconds at an ultrasonic intensity of 60W and a frequency of 40kHz. Remove the aluminum foil, filter the ultrasonically treated aqueous solution, and dry the filter cake at 105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The removed aluminum foil is washed clean with the filtrate to obtain high-purity aluminum foil. The washing solution is recycled into the ultrasonic treatment process.

[0065] Example 4

[0066] Weigh out the empty foil area of ​​the positive electrode sheet of a lithium battery with an insulating coating, i.e., the current collector aluminum foil with an insulating coating. Heat treat it at 350℃ for 100 minutes. After cooling to room temperature, put it into deionized water with 0.005‰ of leucine added to the total weight of the heat-treated material cooled to room temperature. Ultrasonically treat it for 20 seconds at an ultrasonic intensity of 50W and a frequency of 35kHz. Take out the aluminum foil, filter the ultrasonically treated aqueous solution, and dry the filter cake at 105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The aluminum foil taken out is washed clean with the filtrate to obtain high-purity aluminum foil. The washing solution is recycled into the ultrasonic treatment process.

[0067] Example 5

[0068] Weigh out the empty foil area of ​​the positive electrode of a lithium battery with an insulating coating, i.e., the current collector aluminum foil with an insulating coating. Heat treat it at 400℃ for 50 minutes, cool it to room temperature, and then put it into deionized water containing 0.008‰ of the total weight of the heat-treated and cooled materials in a mixture of ethanol, glutamic acid and lysine (mass ratio 1:2:1). Ultrasonically treat it for 5 seconds at an ultrasonic intensity of 15W and a frequency of 30kHz. Remove the aluminum foil, filter the ultrasonically treated aqueous solution, and dry the filter cake at 105℃ to obtain high-purity boehmite. The filtrate is recycled into the aluminum foil washing process. The aluminum foil is washed clean with the filtrate to obtain high-purity aluminum foil. The washing solution is recycled into the ultrasonic treatment process.

[0069] Comparative Example 1

[0070] The amount of the weak ultrasonic treatment additive in this comparative example is 0.0005‰ of the total weight of the material after heat treatment and cooling to room temperature. All other steps are the same as in Example 1.

[0071] Comparative Example 2

[0072] The amount of the weak ultrasonic treatment additive in this comparative example is 0.06‰ of the total weight of the material after heat treatment and cooling to room temperature. All other steps are the same as in Example 1.

[0073] Comparative Example 3

[0074] The heat treatment temperature in this comparative example is 260°C, and all other steps are the same as in Example 1.

[0075] Comparative Example 4

[0076] The heat treatment temperature in this comparative example is 500°C, and all other steps are the same as in Example 1.

[0077] Comparative Example 5

[0078] The ultrasonic intensity described in this comparative example is 3W, and all other steps are the same as in Example 1.

[0079] Comparative Example 6

[0080] The ultrasonic intensity described in this comparative example is 80W, and all other steps are the same as in Example 1.

[0081] Comparative Example 7

[0082] The ultrasonic frequency described in this comparative example is 15kHz, and all other steps are the same as in Example 1.

[0083] Comparative Example 8

[0084] The ultrasonic frequency described in this comparative example is 45kHz, and all other steps are the same as in Example 1.

[0085] Comparative Example 9

[0086] The ultrasonic treatment time in this comparative example is 0.5s, and all other steps are the same as in Example 1.

[0087] Comparative Example 10

[0088] The ultrasonic treatment time in this comparative example is 40 seconds, and all other steps are the same as in Example 1.

[0089] Comparative Example 11

[0090] The heat treatment time in this comparative example is 5 minutes, and all other steps are the same as in Example 1.

[0091] Comparative Example 12

[0092] The heat treatment time in this comparative example is 180 min, and all other steps are the same as in Example 1.

[0093] The reaction conditions and purity of the final products in Examples 1-5 and Comparative Examples 1-12 are statistically analyzed as shown in Table 1.

[0094] Table 1. Statistical results of reaction conditions and purity of final products in the examples and comparative examples.

[0095]

[0096]

[0097] The data in Table 1 shows that:

[0098] In Comparative Example 1, the amount of the weak ultrasonic treatment additive added was 0.0005‰ of the total weight of the material after heat treatment and cooling to room temperature. Because the amount of weak ultrasonic treatment additive in this comparative example was too small, the additive did not have a sufficient effect on promoting the decomposition and peeling of the coating adhesive, resulting in incomplete decomposition and peeling of the coating adhesive and low purity of the recovered boehmite and aluminum foil.

[0099] In Comparative Example 2, the amount of weak ultrasonic treatment additive added was 0.06‰ of the total weight of the material after heat treatment and cooling to room temperature. Because the amount of weak ultrasonic treatment additive in this comparative example was too high, the residual amount of the additive in the recovered boehmite was too high, and the purity of the recovered boehmite was low.

[0100] In Comparative Example 3, the heat treatment temperature was 260℃. Because the heat treatment temperature in this comparative example was too low, the decomposition rate of the coating adhesive was too low, which caused too much decomposition pressure to the subsequent weak ultrasonic treatment. As a result, the decomposition and peeling of aluminum by the coating adhesive was too low, and the purity of the recovered boehmite and aluminum foil was low.

[0101] In Comparative Example 4, the heat treatment temperature was 500℃. Due to the excessively high heat treatment temperature in this comparative example, some boehmite decomposed, resulting in a lower recovery rate of boehmite.

[0102] In Comparative Example 5, the ultrasonic intensity was 3W. Due to the low ultrasonic intensity in this comparative example, the effect of further promoting the decomposition and peeling of the coating adhesive was insufficient, resulting in incomplete decomposition and peeling of the coating adhesive and low purity of the recovered boehmite and aluminum foil.

[0103] In Comparative Example 6, the ultrasonic intensity was 80W. Due to the excessively high ultrasonic intensity in this comparative example, the aluminum foil of the current collector was damaged, causing some aluminum particles or powder to enter the aqueous solution and then into the recovered boehmite, resulting in low purity of the recovered boehmite.

[0104] In Comparative Example 7, the ultrasonic frequency was 15kHz. Because the ultrasonic frequency in this comparative example was too low, the effect of further promoting the decomposition and peeling of the coating adhesive was insufficient, resulting in incomplete decomposition and peeling of the coating adhesive and low purity of the recovered boehmite and aluminum foil.

[0105] In Comparative Example 8, the ultrasonic frequency was 45kHz. Because the ultrasonic frequency in this comparative example was too high, it damaged the aluminum foil of the current collector, causing some aluminum particles or powder to enter the aqueous solution and then enter the recovered boehmite, resulting in low purity of the recovered boehmite.

[0106] In Comparative Example 9, the ultrasonic treatment time was 0.5s. Because the ultrasonic treatment time in this comparative example was too short, the effect of further promoting the decomposition and peeling of the coating adhesive was insufficient, resulting in incomplete decomposition and peeling of the coating adhesive and low purity of the recovered boehmite and aluminum foil.

[0107] In Comparative Example 10, the ultrasonic treatment time was 40 seconds. Because the ultrasonic treatment time in this comparative example was too long, it damaged the aluminum foil of the current collector, causing some aluminum particles or powder to enter the aqueous solution and then enter the recovered boehmite, resulting in low purity of the recovered boehmite.

[0108] In Comparative Example 11, the heat treatment time was 5 minutes. Because the heat treatment time in this comparative example was too short, the decomposition rate of the coating adhesive was too low, which caused too much decomposition pressure to the subsequent weak ultrasonic treatment. As a result, the decomposition and peeling of aluminum by the coating adhesive was too low, and the purity of the recovered boehmite and aluminum foil was low.

[0109] In Comparative Example 12, the heat treatment time was 180 minutes. This heat treatment time was too long and the energy consumption was too high.

[0110] In Examples 1-5, the purity of the recovered boehmite was higher than 99.9%, and the purity of the recovered aluminum foil was higher than 99.8%.

[0111] In summary, the present application provides a method for recovering aluminum foil and boehmite from lithium-ion batteries: (1) Low-energy decomposition of insulating coating adhesive is achieved by using low-temperature, short-time heat treatment, and weak ultrasonic treatment is assisted by additives to further promote the decomposition of adhesive, thereby achieving efficient separation of coating material and aluminum foil.

[0112] (2) High added value of recycled products: The main component of the recycled high-purity boehmite is boehmite, with a mass fraction greater than 99.9%. It can be reused as a raw material for the insulating coating of lithium battery positive electrode; the main component of the recycled high-purity aluminum foil is aluminum, with a mass fraction greater than 99.8%, and it can be recycled as a raw material for battery-grade aluminum foil.

[0113] (3) The solution is recycled throughout the process with no wastewater discharge.

[0114] (4) It features low energy consumption, short process, simple operation, easy industrialization and stable production, and zero waste discharge.

[0115] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for recovering aluminum foil and boehmite from lithium-ion batteries, characterized in that, The method includes: A current collector aluminum foil with an insulating coating is obtained for use in lithium-ion batteries; The current collector aluminum foil is heat-treated to decompose the insulating coating and obtain the material. The material is mixed with a solution containing additives and then subjected to ultrasonic treatment to decompose the residual insulating coating and completely separate the insulating coating from the aluminum foil, resulting in aluminum foil and a solution containing high-purity boehmite. The heat treatment process parameters include: temperature 290℃~480℃, time 10min~150min; The ultrasonic treatment process parameters include: power 5W~60W, frequency 20kHz~40kHz, and time 1s~30s. The additive includes at least one of the following: alcohols, surfactants, and amino acids; the additive is 0.001 parts by weight to 0.01 parts by weight relative to 1000 parts by weight of the material. The alcohols include at least one of the following: ethanol and methanol; The surfactant includes at least one of the following: sodium dodecyl sulfate and sodium dodecylbenzene sulfonate; The amino acids include at least one of the following: glycine, alanine, valine, leucine, glutamic acid, and lysine.

2. The method according to claim 1, characterized in that, The insulating coating comprises polyvinylidene fluoride.

3. The method according to claim 1, characterized in that, The process involves mixing the material with a solution containing additives, followed by ultrasonic treatment to decompose the residual insulating coating and completely separate the insulating coating from the aluminum foil, yielding aluminum foil and a solution containing high-purity boehmite. The process further includes: The solution containing high-purity boehmite was filtered to obtain filtrate and high-purity boehmite wet cake. The high-purity boehmite wet cake is dried to obtain high-purity boehmite; The aluminum foil was washed with the filtrate to obtain high-purity aluminum foil; The filtrate after washing the aluminum foil is returned to the ultrasonic treatment to achieve the recycling of the filtrate.

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