Stripping agent and method for separating spent lithium-ion battery cathode active material from cathode current collector

Abstract

The application provides a stripping agent and method for separating positive active material and positive current collector of waste lithium ion battery, and belongs to the field of lithium ion battery recycling. The stripping agent comprises a foaming component and a solvent component. The foaming component is used to generate gas after electron irradiation treatment. The solvent component is used to dissolve and disperse the foaming component, and also used to swell the binder PVDF in the positive electrode of the waste lithium ion battery, so as to reduce the overflow of the gas. In the stripping method, the stripping agent is used to penetrate the positive electrode of the waste lithium ion battery first, and then the positive electrode of the waste lithium ion battery is subjected to electron irradiation treatment, so as to induce the stripping agent between the positive active material and the current collector to generate gas, and the positive active material and the current collector are forced to separate through the expansion of the gas. The application can solve the problems of the existing recycling method, such as high pollution and energy consumption, low economic and environmental benefits, and the recycled material cannot be directly processed.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery recycling, and more specifically, relates to a stripping agent and stripping method for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries. Background Technology

[0002] The production process and the end of the battery lifecycle inevitably generate a large number of waste lithium battery electrodes. These electrodes contain a large amount of lithium, cobalt, nickel, manganese, aluminum and other metal elements, and recycling these waste lithium battery electrodes has significant value.

[0003] Currently, the mainstream recycling methods in the industry are pyrometallurgical or hydrometallurgical processes. These processes generate high pollution and energy consumption, resulting in low economic and environmental benefits, and yielding only a single element rather than cathode material that can be directly processed further. Therefore, providing a simple and efficient process for stripping cathodes from spent lithium batteries, facilitating subsequent remediation, is of great significance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a stripping agent and stripping method for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries. This invention aims to solve the problems of high pollution and energy consumption, low economic and environmental benefits, and the inability of the recycled materials obtained to be directly processed in existing recycling methods.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a stripping agent for separating the positive electrode active material and the positive electrode current collector of a waste lithium-ion battery is provided, comprising a foaming component and a solvent component, wherein the foaming component and the solvent component are mixed uniformly, the foaming component is used to decompose and generate gas after electron irradiation treatment, and the solvent component is used to dissolve and disperse the foaming component, and also to cause the binder PVDF in the positive electrode of the waste lithium-ion battery to swell, thereby reducing the leakage of the gas.

[0006] Furthermore, the foaming component is one or more of azo foaming agents, sulfonyl hydrazine foaming agents, aminourea foaming agents, and organic peroxide foaming agents, and the solvent component is one or more of ethers, alcohols, ketones, and esters.

[0007] Furthermore, by mass percentage, the foaming component in the stripping agent comprises 2% to 3.2%, and the solvent component comprises 96.8% to 98%.

[0008] Furthermore, the azo blowing agent is one or more of 2,2′-azobisisobutyronitrile, diisopropyl azodicarbonate, and diethyl azodicarbonate; the sulfonyl hydrazine blowing agent is one or more of benzenesulfonyl hydrazine, p-toluenesulfonyl hydrazine, 4,4'-oxobis(benzenesulfonyl hydrazine), 1,3-benzenedisulfonyl hydrazine, and 3,3'-disulfonyl hydrazine diphenyl sulfone; the hydroxyurea blowing agent is one or more of p-toluenesulfonamide, 4,4'-oxobis(benzenesulfonamide), and azodicarbonamide; the ether solvent is one or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, and tert-butyl ether; the alcohol solvent is one or more of ethanol, ethylene glycol, propanol, and glycerol; and the ketone solvent is one or more of acetone, butanone, and N-methylpyrrolidone.

[0009] In fact, azo foaming agents, sulfonyl hydrazine foaming agents, aminourea foaming agents, and organic peroxide foaming agents are not limited to the specific substances listed above. They can all meet the following conditions: (1) They can decompose under the action of free radicals and produce a large amount of gas, including but not limited to nitrogen, carbon dioxide, oxygen, etc.; (2) The decomposition products will not cause significant damage to the positive electrode active material. As long as the above two points are met, they can be used as foaming agents. The solvent components are not limited to one or more of ethers, alcohols, ketones, and esters, nor are they limited to the specific types mentioned above. They can all meet the following conditions: They can fully and effectively dissolve the above foaming agents and do not cause significant damage to the positive electrode active material. They can all be used as solvents.

[0010] According to a second aspect of the present invention, a method for separating the positive electrode active material and the positive electrode current collector of a waste lithium-ion battery is also provided. First, the waste lithium-ion battery positive electrode is permeated with the stripping agent as described above to ensure that there is sufficient stripping agent between the positive electrode active material and the current collector. Then, the waste lithium-ion battery positive electrode is subjected to electron irradiation treatment to induce the generation of gas between the stripping agent and the current collector. The expansion of the gas forces the positive electrode active material and the current collector to separate.

[0011] Furthermore, the positive electrode of the spent lithium-ion battery is immersed in a stripping agent to achieve penetration of the stripping agent into the positive electrode. The immersion time t is related to the coating thickness h of the positive electrode active material, satisfying the following formula:

[0012] t≥A×(e Bh -1)(h)

[0013] Where A and B are constants depending on the type of active material. For nickel-cobalt-manganese ternary active materials, constant A is 2.79 and constant B is 0.0032. For lithium iron phosphate active materials, constant A is 0.92 and constant B is 0.0062. The unit of constant A is square centimeter-hour, abbreviated as cm. 2 ×h, the unit of the constant B is micrometers per square centimeter, abbreviated as (cm).2 μm) -1 , the area S of the positive electrode of the waste lithium-ion battery is in square centimeters, abbreviated as cm 2 , and the unit of the thickness h is micrometers, abbreviated as μm.

[0014] Furthermore, when the soaking time t is greater than or equal to the lower limit of the formula, the stripping rate is greater than or equal to 95%. When the soaking time t is less than the lower limit of the formula, the stripping agent cannot fully penetrate between the positive electrode active material and the current collector, and the stripping rate is less than 95%.

[0015] Furthermore, the waste lithium-ion for which the positive electrode active material is a nickel-cobalt-manganese ternary material and a lithium iron phosphate material. The active material in the positive electrode sheet of the waste lithium-ion battery is a nickel-cobalt-manganese ternary material or / and a lithium iron phosphate material. The chemical formula of the nickel-cobalt-manganese ternary material is LiNi 1-x-y Co x Mn y O2, where 0 < x < 1, 0 < y < 1, and (1 - x - y):x:y is 1:1:1, 4:2:4, 5:2:3, 6:2:2 or 8:1:1. The chemical formula of the lithium iron phosphate material is LiFePO4.

[0016] Furthermore, free radicals are generated by electron beam irradiation to promote the generation of one or more of nitrogen, carbon dioxide, and carbon monoxide in the foaming component of the stripping agent. The electron beam irradiation treatment is the irradiation of the pretreated waste positive electrode sheet with a high-energy electron beam.

[0017] Furthermore, after stripping, the positive electrode active material and the current collector are separated, and the obtained positive electrode active material is washed with a solvent. The solvent is one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Mechanical means can be used to separate the positive electrode active material and the current collector to obtain the stripped waste positive electrode active material. The positive electrode active material obtained after washing with the solvent

[0018] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following

[0019] Advantages are as follows:

[0020] On the one hand, the present invention provides a stripping agent for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries. It is mainly formed by uniformly mixing foaming components and solvent components. The foaming component is used to decompose and generate gas after electron irradiation treatment. The gas expands during the process of its formation, causing the positive electrode active material and the current collector, which are bonded together, to naturally crack and separate. The solvent component is used to dissolve and disperse the foaming component, and also to cause the PVDF binder in the positive electrode of the waste lithium-ion battery to swell. After the PVDF swells, it can form a local closed space for the generated gas, thus providing its benefits, and can also promote the degradation of the positive electrode active material itself, achieving multiple benefits.

[0021] On the other hand, this invention provides a method for separating the positive electrode active material and the positive electrode current collector of waste lithium batteries using the above-mentioned stripping agent. First, the stripping agent is used to permeate the positive electrode of the waste lithium-ion battery, and then the positive electrode of the waste lithium-ion battery is subjected to electron beam irradiation treatment. The electron beam irradiation generates free radicals, which cause the foaming component in the stripping agent to generate one or more of nitrogen, carbon dioxide, and oxygen. Simultaneously, the solvent component causes the PVDF to swell. The swelling of PVDF forms a closed space for the gas. The gas expansion can relatively easily achieve the separation of the positive electrode active material and the positive electrode current collector. This method has simple steps, low energy consumption, and can generate significant economic benefits. It can be effectively promoted and used in engineering practice. Attached Figure Description

[0022] Figure 1 This invention provides a method for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] To illustrate the method of the present invention in more detail, the following detailed description is provided in conjunction with specific embodiments.

[0025] Figure 1 This invention provides a method for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries. As shown in the figure, a stripping agent is first prepared, then the waste electrode sheets are soaked, followed by electron beam irradiation treatment, and finally, the stripped battery positive electrode active material is cleaned with a solvent.

[0026] Example 1

[0027] This example uses nickel-cobalt-manganese ternary LiNi alloy waste from industrial production. 0.5 Co 0.2 Mn0.3 Take O2 (NCM523) material as an example.

[0028] First, a stripping agent is prepared by mixing 2.6% by mass of 2,2′-azobisisobutyronitrile and 97.4% by mass of diethyl ether, and stirring until the 2,2′-azobisisobutyronitrile is completely dissolved.

[0029] Next, the NCM523 electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0030] t≥A×(e Bh -1)(h)

[0031] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given by the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect of the active material. For nickel-cobalt-manganese ternary materials, constant A is approximately 2.79 and B is 0.0032. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0032] The measured value of the scrapped nickel-cobalt-manganese ternary LiNi in this embodiment was... 0.5 Co 0.2 Mn 0.3 The O2 (NCM523) material coating thickness is 300 μm, and based on empirical formulas, the required pretreatment time is predicted to be 4.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0033]

[0034] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0035] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate nitrogen gas. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0036] Finally, the electron beam-irradiated electrode sheets are cleaned with N-methylpyrrolidone, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to finally obtain pure waste positive electrode active material powder.

[0037] Example 2

[0038] This example uses nickel-cobalt-manganese ternary LiNi lithium-ion batteries that have actually been cycled to the point of disposal. 0.4 Co 0.2 Mn 0.4 Take O2 (NCM424) material as an example.

[0039] First, a stripping agent is prepared by mixing 3% by mass of diisopropyl azodicarbonate and 97% by mass of acetone, and stirring until the diisopropyl azodicarbonate is completely dissolved.

[0040] Next, the NCM424 electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0041] t≥A×(e Bh -1)(h)

[0042] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given by the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect of the active material. For nickel-cobalt-manganese ternary materials, constant A is approximately 2.79 and B is 0.0032. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0043] The measured value of the scrapped nickel-cobalt-manganese ternary LiNi in this embodiment was... 0.4 Co 0.2 Mn 0.4 The O2 (NCM424) material coating thickness is 300 μm, and based on empirical formulas, the required pretreatment time is predicted to be 4.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0044] Preprocessing time / h 1 2 3.5 4.5 5 Peeling rate / % 69.1 80.4 86.9 95.2 95.9

[0045] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0046] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate nitrogen gas. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0047] Finally, the electron beam-irradiated electrode sheets are cleaned with dimethylformamide, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to obtain pure waste positive electrode active material powder.

[0048] Example 3

[0049] This example uses nickel-cobalt-manganese ternary LiNi lithium-ion batteries that have actually been cycled to the point of disposal. 1 / 3 Co 1 / 3 Mn 1 / 3 Take O2 (NCM111) material as an example.

[0050] First, a stripping agent is prepared by mixing 2.3% by mass of benzenesulfonyl hydrazine and 97.7% by mass of butanone, and stirring until the benzenesulfonyl hydrazine is completely dissolved.

[0051] Next, the NCM111 electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0052] t≥A×(e Bh -1)(h)

[0053] For nickel-cobalt-manganese ternary materials, the constants A and B are approximately 2.79 and 0.0032, respectively. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0054] The measured value of the scrapped nickel-cobalt-manganese ternary LiNi in this embodiment was... 1 / 3 Co 1 / 3 Mn 1 / 3 The O2 (NCM111) material coating thickness is 200 μm, and based on empirical formulas, the required pretreatment time is predicted to be 2.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0055] Preprocessing time / h 0.5 1.5 2 2.5 3 Peeling rate / % 65.8 81.6 90.1 95.2 96.9

[0056] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0057] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate nitrogen gas. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0058] Finally, the electron beam-irradiated electrode sheets are cleaned with dimethylacetamide, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to obtain pure waste positive electrode active material powder.

[0059] Example 4

[0060] This example uses nickel-cobalt-manganese ternary LiNi lithium-ion batteries discarded in industrial production. 0.6 Co 0.2 Mn 0.2 Take O2 (NCM622) material as an example.

[0061] First, a stripping agent is prepared by mixing 2.0% by mass of p-toluenesulfonamide and 98.0% by mass of tetrahydrofuran, and stirring until the p-toluenesulfonamide is completely dissolved.

[0062] Next, the NCM622 electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0063] t≥A×(e Bh -1)(h)

[0064] For nickel-cobalt-manganese ternary materials, the constants A and B are approximately 2.79 and 0.0032, respectively. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0065] The measured value of the scrapped nickel-cobalt-manganese ternary LiNi in this embodiment was... 0.6 Co 0.2 Mn 0.2The O2 (NCM622) material coating thickness is 300 μm, and based on empirical formulas, the required pretreatment time is predicted to be 4.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0066] Preprocessing time / h 1 2 3.5 4.5 5 Peeling rate / % 72.1 81.8 89.9 95.4 96.1

[0067] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0068] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam, causing the foaming component in the stripping agent to produce nitrogen and carbon dioxide. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0069] Finally, the electron beam-irradiated electrode sheets are cleaned with dimethyl sulfoxide, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to obtain pure waste positive electrode active material powder.

[0070] Example 5

[0071] This example uses nickel-cobalt-manganese ternary LiNi lithium-ion batteries discarded in industrial production. 0.8 Co 0.1 Mn 0.1 Take O2 (NCM811) material as an example.

[0072] First, a stripping agent is prepared by mixing 2.9% by mass of 4,4'-bis(benzenesulfonyl)hydrazine oxide and 97.1% by mass of N-methylpyrrolidone, and stirring until the 4,4'-bis(benzenesulfonyl)hydrazine oxide is completely dissolved.

[0073] Next, the NCM811 electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0074] t≥A×(e Bh -1)(h)

[0075] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given in the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect. For nickel-cobalt-manganese ternary materials, constant A is approximately 2.79 and B is 0.0032; for lithium iron phosphate materials, constant A = 0.92 and constant B is 0.0062. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0076] The measured value of the scrapped nickel-cobalt-manganese ternary LiNi in this embodiment was... 0.8 Co 0.1 Mn 0.1 The O2 (NCM811) material coating thickness is 200 μm, and based on empirical formulas, the required pretreatment time is predicted to be 2.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0077] Preprocessing time / h 0.5 1.5 2 2.5 3 Peeling rate / % 66.7 82.6 89.6 95.1 95.9

[0078] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0079] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate nitrogen gas. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0080] Finally, the electron beam-irradiated electrode sheets are cleaned with N-methylpyrrolidone, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to finally obtain pure waste positive electrode active material powder.

[0081] Example 6

[0082] This example uses lithium iron phosphate (LiFePO4) (LFP) material from scrapped lithium-ion batteries in industrial production.

[0083] First, a stripping agent is prepared by mixing 3.2% by mass of 2,2′-azobisisobutyronitrile and 96.48% by mass of ethanol and stirring until the 2,2′-azobisisobutyronitrile is completely dissolved.

[0084] Next, the LFP electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0085] t≥A×(e Bh -1)(h)

[0086] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given in the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect. For lithium iron phosphate materials, constant A = 0.92 and constant B = 0.0062. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0087] The coating thickness of the scrapped lithium iron phosphate (LiFePO4) (LFP) material from industrial production in this embodiment was measured to be 300 μm. Based on empirical formulas, the required pretreatment time was predicted to be 4.9 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0088] Preprocessing time / h 1 2 3.5 4.5 5 Peeling rate / % 66.1 78.6 89.3 93.5 95.8

[0089] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0090] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate nitrogen gas. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 300 kgy, and the irradiation time was 30 s. Slight shedding of the surface-active material was observed after irradiation.

[0091] Finally, the electron beam-irradiated electrode sheets are cleaned with dimethylformamide, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to obtain pure waste positive electrode active material powder.

[0092] Example 7

[0093] This example uses lithium iron phosphate (LiFePO4) (LFP) material from a lithium-ion battery that has actually been recycled to waste.

[0094] First, a stripping agent is prepared by mixing 2.1% by mass of p-toluenesulfonamide and 97.9% by mass of N-methylpyrrolidone, and stirring until p-toluenesulfonamide is completely dissolved.

[0095] Then, the LFP electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0096] t≥A×(e Bh -1)(h)

[0097] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given in the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect. For lithium iron phosphate materials, constant A = 0.92 and constant B = 0.0062. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0098] The coating thickness of the scrapped lithium iron phosphate (LiFePO4) (LFP) material from industrial production in this embodiment was measured to be 200 μm. Based on empirical formulas, the required pretreatment time was predicted to be 2.5 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0099] Preprocessing time / h 0.5 1.5 2 2.5 3 Peeling rate / % 71.5 88.8 93.4 95.4 96.2

[0100] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0101] Next, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam to induce the foaming component in the stripping agent to generate high-energy electron beam energy of 0.5 MeV, irradiation dose of 300 kgy, and irradiation time of 30 s. Slight shedding of the surface active material was observed after irradiation.

[0102] Finally, the electron beam-irradiated electrode sheets are cleaned with N-methylpyrrolidone, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to finally obtain pure waste positive electrode active material powder.

[0103] Example 8

[0104] This example uses lithium iron phosphate (LiFePO4) (LFP) material from a lithium-ion battery that has actually been recycled to waste.

[0105] First, a stripping agent is prepared by mixing 2.9% by mass of azodicarbonamide and 97.1% by mass of dimethylformamide, and stirring until the azodicarbonamide is completely dissolved.

[0106] Next, the LFP electrode is immersed in the prepared stripping agent. Specifically, the stripping agent pretreatment time t is related to the coating thickness h of the positive electrode active material, satisfying the following empirical formula:

[0107] t≥A×(e Bh -1)(h)

[0108] Where A and B are constants depending on the type of active material. Extensive experiments have shown that the stripping agent treatment time should be greater than or equal to the lower limit given in the above formula to ensure a stripping rate greater than or equal to 95%. If it is less than this value, the stripping agent cannot completely penetrate between the positive electrode active material and the current collector, resulting in poor stripping effect. For lithium iron phosphate materials, constant A = 0.92 and constant B = 0.0062. These values ​​were obtained through extensive experiments. The unit of constant A is square centimeter-hour (cm²). 2 ×h), the unit of the constant B is micrometers per square centimeter (cm). 2 μm) -1 The area S of the waste electrode sheet is measured in square centimeters (cm²). 2 The thickness h is in micrometers (μm).

[0109] The coating thickness of the scrapped lithium iron phosphate (LiFePO4) (LFP) material from industrial production in this embodiment was measured to be 300 μm. Based on empirical formulas, the required pretreatment time was predicted to be 4.9 h. Further actual testing revealed the relationship between different pretreatment times and peeling rates, as shown in the table below.

[0110] Preprocessing time / h 1 2 3.5 4.5 5 Peeling rate / % 66.7 79.3 91.6 94.5 95.8

[0111] The actual test results show that they match the theoretical expectations, indicating that the empirical formula is reliable.

[0112] Then, after pretreatment, the surface of the pretreated positive electrode was irradiated with a high-energy electron beam, causing the foaming component in the stripping agent to generate nitrogen and carbon monoxide. The high-energy electron beam irradiation energy was 0.5 MeV, the irradiation dose was 290 kgy, and the irradiation time was 35 s. Slight shedding of the surface-active material was observed after irradiation.

[0113] Finally, the electron beam-irradiated electrode sheets are cleaned with dimethylformamide, and the positive electrode active material and current collector are separated by mechanical means. The stripped positive electrode active material is further crushed by mechanical means to obtain pure waste positive electrode active material powder.

[0114] In the above embodiments, the azo blowing agents involved are 2,2′-azobisisobutyronitrile and diisopropyl azodicarboxylate. In fact, diethyl azodicarboxylate, which decomposes to produce nitrogen gas, can also be used. The sulfonyl hydrazine blowing agents involved are benzenesulfonyl hydrazine and 4,4'-oxobis(benzenesulfonyl hydrazine). In fact, p-toluenesulfonyl hydrazine, 1,3-benzenedisulfonyl hydrazine, and 3,3'-disulfonyl hydrazine diphenyl sulfone are also acceptable, because p-toluenesulfonyl hydrazine, 1,3-benzenedisulfonyl hydrazine, and 3,3'-disulfonyl hydrazine diphenyl can all decompose to produce nitrogen gas and carbon dioxide. The hydroxyurea blowing agent involved is p-toluenesulfonamide. In fact, 4,4'-oxobis(benzenesulfonamide) and azodicarbonamide are also feasible, because they all decompose to produce nitrogen gas. The ether solvents involved are diethyl ether and tetrahydrofuran. In fact, methyl tert-butyl ether and tert-butyl ether are also suitable, as they can dissolve the aforementioned blowing agent components. The alcohol solvent involved is ethanol. In fact, ethylene glycol, propanol, and glycerol are also suitable, as they can dissolve the aforementioned blowing agent components.

[0115] The method of this invention can separate the positive electrode sheet of waste lithium-ion batteries to obtain waste lithium-ion battery positive electrode active material and aluminum foil in powder form. (The aluminum foil has been removed.) The powder can be reused after further repair processing.

[0116] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A stripping agent for separating the positive electrode active material from the positive electrode current collector of waste lithium-ion batteries, characterized in that, The mixture includes a foaming component and a solvent component, which are uniformly mixed. The foaming component is used to decompose and generate gas after electron irradiation treatment. The solvent component is used to dissolve and disperse the foaming component, and also to cause the binder in the positive electrode of spent lithium-ion batteries to swell, thereby reducing the leakage of the gas. The foaming component is one or more of the following: azo foaming agents, sulfonyl hydrazine foaming agents, aminourea foaming agents, and organic peroxide foaming agents.

2. The stripping agent as described in claim 1, characterized in that, The solvent component is one or more of ethers, alcohols, ketones, and esters.

3. The stripping agent as described in claim 2, characterized in that, The foaming component in the stripping agent has a mass percentage of 2% to 3.2%, and the solvent component has a mass percentage of 96.8% to 98%.

4. The stripping agent as described in claim 3, characterized in that, The azo foaming agent is one or more of 2,2′-azobisisobutyronitrile, diisopropyl azodicarbonate, and diethyl azodicarbonate. Sulfonyl hydrazide foaming agents include one or more of benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, 4,4'-oxobisbenzenesulfonyl hydrazide, 1,3-benzenedisulfonyl hydrazide, and 3,3'-disulfonyl hydrazide diphenyl sulfone. Aminourea foaming agents are one or more of p-toluenesulfonamide, 4,4'-oxobis(benzenesulfonamide), and azodicarbonamide. The ether solvent is one or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, and tert-butyl ether. The alcohol solvent is one or more of ethanol, ethylene glycol, propanol, and glycerol. The ketone solvent is one or more of acetone, butanone, and N-methylpyrrolidone.

5. A method for separating the positive electrode active material and the positive electrode current collector of waste lithium-ion batteries, characterized in that, First, the waste lithium-ion battery positive electrode is permeated with the stripping agent as described in any one of claims 1-4 to ensure sufficient stripping agent between the positive electrode active material and the current collector. Then, the waste lithium-ion battery positive electrode is subjected to electron irradiation treatment to induce the generation of gas between the stripping agent between the positive electrode active material and the current collector. The expansion of the gas forces the positive electrode active material and the current collector to separate.

6. The method as described in claim 5, characterized in that, The positive electrode of the spent lithium-ion battery is immersed in a stripping agent to allow the stripping agent to penetrate the positive electrode of the spent lithium-ion battery. The immersion time t is related to the coating thickness h of the positive electrode active material, and satisfies the following formula: Where A and B are constants depending on the type of active material. For nickel-cobalt-manganese ternary active materials, constant A is 2.79 and constant B is 0.0032. For lithium iron phosphate active materials, constant A is 0.92 and constant B is 0.0062. The unit of constant A is square centimeter-hour, and the unit of constant B is micrometer per square centimeter. The unit of positive electrode area S of waste lithium-ion batteries is square centimeters, and the unit of thickness h is micrometer.

7. The method as described in claim 6, characterized in that, When the soaking time t is greater than or equal to the lower limit of the formula, the peeling rate is greater than or equal to 95%. When the soaking time t is less than the lower limit of the formula, the peeling agent cannot completely penetrate between the positive electrode active material and the current collector, and the peeling rate is less than 95%.

8. The method as described in claim 7, characterized in that, The positive electrode active materials used are waste nickel-cobalt-manganese ternary materials and waste lithium iron phosphate materials.

9. The method as described in claim 5, characterized in that, Free radicals are generated by electron beam irradiation, which causes the foaming components in the stripping agent to produce one or more of nitrogen, carbon dioxide, and carbon monoxide.

10. The method as described in claim 8 or 9, characterized in that, After stripping, the positive electrode active material and the current collector are separated, and the obtained positive electrode active material is cleaned with a solvent, wherein the solvent is one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

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