Method for recycling lithium battery slurry in waste filter element

Abstract

The invention relates to the field of battery slurry recovery, in particular to a method for recycling lithium battery slurry in a waste filter element. The method comprises the following steps: carrying out graded cutting and stripping according to a multi-layer composite material of the cyst filter element, sequentially recovering a filter element shell, a supporting layer, a central drainage tube and other structural parts, carrying out low-temperature freezing embrittlement on a core filter membrane layer, stripping recyclable slurry, carrying out solid-liquid separation to obtain a slurry solution, filtering, drying and purifying, and recovering positive and negative electrode slurry. The method is convenient to operate, the structural part of the scrapped cyst filter element and the slurry attached to the surface of the scrapped cyst filter element can be recycled at the same time, the problem that due to the multi-layer composite structure of the cyst filter element, slurry stripping is not thorough is effectively solved, the structural part can be used for new filter element production after being recycled, and a solution in the process is recycled conveniently, can be reused and is harmless to the environment; recycled slurry can be directly added for lithium battery production through a specific process, and material loss is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of battery slurry recycling, and more particularly to a method for recycling and reusing lithium battery slurry from waste filter cartridges. Background Technology

[0002] In the production process of lithium-ion batteries, both the positive and negative electrode slurries need to be filtered multiple times through filter cartridges to remove impurities before being conveyed to the coating die. As filtration time increases, the amount of impurities adsorbed by the filter cartridges increases until they become clogged and fail, requiring replacement. The replaced waste filter cartridges contain a large amount of residual slurry (including the main positive and negative electrode materials, conductive agents, binders, dispersants, etc.). The traditional industry method is to directly discard the filter cartridges, resulting in the waste of valuable metal resources such as lithium, cobalt, and manganese. Furthermore, the waste filter cartridges contain organic solvents such as NMP, which are corrosive and pollute the environment, posing environmental risks. Commonly used NMP filters in the industry are generally made of plastic (PP / nylon). Recycling them involves directly using mechanical stripping to remove the slurry from the filter cartridge surface, which is inefficient and easily damages the slurry composition. Directly landfilling the waste filter cartridges without recycling leads to environmental pollution, as each waste filter cartridge contains 1-4 kg of positive and negative electrode slurry, resulting in significant waste. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for recycling and reusing lithium battery slurry from waste filter cartridges.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for recycling and reusing lithium battery slurry from waste filter cartridges is provided, comprising the following steps:

[0006] S1. After disassembling the waste filter element, the filter membrane is subjected to low-temperature freezing treatment to obtain agglomerated slurry.

[0007] S2. Dissolve the agglomerated slurry in a solvent, and then perform ultrasonic treatment, impurity removal treatment and purification treatment in sequence to obtain the slurry.

[0008] S3. Perform performance testing on the slurry. If the performance does not meet the standard, repeat step S2 until the slurry performance meets the standard, and then qualified recycled slurry is obtained.

[0009] S4. In the lithium battery slurry dispersion step, the qualified recycled slurry is mixed with the conventional slurry to obtain qualified lithium battery slurry, which can then be discharged for the next step.

[0010] Preferably, in step S1, the disassembly process includes: using a crusher to break open the surface layer of the filter element, recovering the filter element shell, and then using a cutting machine to cut the drainage pipe and support keel, recovering the drainage pipe and support layer.

[0011] More preferably, the crusher speed is 500-1000 rpm and the cutter gap is 0.5-2 mm.

[0012] Preferably, in step S1, the temperature of the low-temperature freezing treatment is -20°C.

[0013] Preferably, in step S2, the solvent is an N-methylpyrrolidone solvent or a water-based solvent.

[0014] Preferably, in step S2, the ultrasonic treatment includes: treating with ultrasound at 20-40 kHz at 60-70°C for 30-40 minutes.

[0015] Preferably, in step S2, the impurity removal process includes: filtering twice with a 150-mesh sieve, and then filtering once with a 12000GS strong magnetic rod.

[0016] Preferably, in step S2, the purification process includes distillation at 170-180°C.

[0017] Preferably, in step S3, the performance testing standards are: positive electrode slurry fineness ≤ 10 μm, ICP ≤ 1 ppm; negative electrode slurry fineness 30 μm, ICP ≤ 1 ppm.

[0018] Preferably, in step S4, the proportion of qualified recycled slurry in the qualified lithium battery slurry is ≤5%, and the weight of qualified recycled slurry added at one time is ≤50kg.

[0019] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0020] This invention utilizes a graded cutting and peeling process based on the multi-layered composite material of the nacelle filter element. The filter element shell, support layer, and central drainage tube are recovered sequentially. The core filter membrane layer is then cryogenically frozen to remove recyclable slurry. A slurry solution is obtained through solid-liquid separation, and after filtration, drying, and purification, the positive and negative electrode slurries are recovered. This method is easy to operate and can simultaneously recover the structural components and surface slurry of discarded nacelle filter elements. It effectively solves the problem of incomplete slurry peeling caused by the multi-layered composite structure of the nacelle filter element. The recovered structural components can be used in the production of new filter elements. The solution obtained during the process is easily recoverable and reusable, and is environmentally friendly. The recovered slurry can be directly added to lithium battery production through a specific process, greatly reducing material loss. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the technical route of a method for recycling and reusing lithium battery slurry in waste filter cartridges according to an embodiment of the present invention.

[0022] Figure 2 shows the SEM analysis of the positive electrode; in which... Figure 2a It is a conventional positive electrode plate. Figure 2bFor adding recycled slurry to the positive electrode sheet;

[0023] Figure 3 shows the SEM analysis image of the negative electrode; among which... Figure 3a It is a conventional negative electrode. Figure 3b For the negative electrode sheet with added recycled slurry;

[0024] Figure 4 Comparison of battery cycle data between conventional slurry and slurry with added recycled slurry;

[0025] Figure 5 The results show the solid content test results for conventional slurry, the slurry of the examples, and the slurry of the comparative examples;

[0026] Figure 6 Viscosity test results for conventional slurry, example slurry, and comparative slurry;

[0027] Figure 7 The results show the fineness test results for conventional slurry, the slurry of the examples, and the slurry of the comparative examples. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0031] Example

[0032] This embodiment provides a method for recycling and reusing lithium battery slurry from waste filter cartridges, the steps of which include:

[0033] S1. Based on the material composition of the waste filter element, adjust the crusher parameters to break the surface layer using a low speed (500-1000rpm) and small blade gap (0.5-2mm) method, and recover the filter element shell; use a cutting machine to cut the drainage pipe and support keel, and recover the central drainage pipe and support layer in sequence; the remaining core filter membrane covered with slurry is embrittled by low-temperature freezing (-20℃), and then the agglomerated slurry is manually peeled off to recover the core filter membrane.

[0034] S2. Dissolve the agglomerated slurry in a solvent. Soak the positive electrode slurry in N-methylpyrrolidone (NMP) solvent and the negative electrode slurry in a water-based solvent to dissolve the binder in the slurry and ensure that the slurry and solvent are fully dissolved. Apply ultrasound (frequency 20-40kHz) and soak at 70℃ for 30 minutes to accelerate the dissolution of the slurry and improve the recovery efficiency, obtaining positive and negative electrode slurry solutions. Filter twice with a 150-mesh metal sieve and then once with a 12000GS strong magnetic rod to remove impurities. Then, distill at 180℃ to obtain purified slurry. The NMP can be recovered after distillation of the positive electrode slurry solution, and the water-based solvent can be recovered after distillation of the negative electrode slurry solution, realizing closed-loop utilization and being harmless to the environment.

[0035] S3. Perform performance testing on the slurry. After purification, measure the fineness and ICP of the slurry. The fineness of the positive electrode slurry should be ≤10μm and the ICP should be ≤1ppm. The fineness of the negative electrode slurry should be ≤30μm and the ICP should be ≤1ppm. If the test fails, the slurry should be distilled again.

[0036] S4. In the lithium battery slurry dispersion step, add qualified recycled slurry. The proportion of recycled slurry added at one time should be ≤5%, and the weight of recycled slurry added at one time should be ≤50kg. Complete the slurry preparation test according to the process to determine the viscosity, fineness, solid content and other indicators. After all indicators are qualified, the slurry can be discharged for use, thus completing the slurry recycling and reuse.

[0037] Comparative Example

[0038] This comparative example provides a method for recycling and reusing lithium battery slurry from waste filter cartridges;

[0039] In step S4, the proportion of recycled slurry added is 7%.

[0040] The rest are the same as in the example.

[0041] Detection Examples

[0042] SEM analysis was performed on conventional positive electrode, conventional negative electrode, positive electrode with added recycled slurry, and negative electrode with added recycled slurry, as shown in Figures 2-3. After adding recycled slurry, the particle size distribution of the positive and negative electrodes was relatively large, but the dispersion effect between particles was good and there was no abnormal agglomeration. This indicates that under the addition ratio specified in this patent, adding recycled slurry will not affect the microstructure of the electrode.

[0043] Cyclic tests were conducted on batteries made with conventional slurry and batteries made with recycled slurry, respectively. The results are as follows: Figure 4 As shown, the cycle performance of the cells produced from recycled slurry is not significantly different from that of conventional cells, meeting the requirements of mass production processes.

[0044] Solid content, viscosity, and fineness were tested on the conventional slurry, the slurry of the example, and the comparative slurry, respectively. The results are as follows: Figure 5-7As shown, adding different proportions of recycled slurry does not affect the solid content of the product. However, as the proportion increases, the product viscosity decreases and the fineness increases, showing a worsening trend. The viscosity / fineness test of the comparative case (7%) was unqualified.

[0045] In summary, this invention utilizes a graded cutting and peeling process based on the multi-layered composite material of the nacelle filter element. The filter element shell, support layer, and central drainage tube are recovered sequentially. The core filter membrane layer is then subjected to low-temperature cryogenic embrittlement to peel off the recyclable slurry. A slurry solution is obtained through solid-liquid separation, and after filtration, drying, and purification, the positive and negative electrode slurries are recovered. This method is easy to operate and can simultaneously recover the structural components and surface slurry of discarded nacelle filter elements. It effectively solves the problem of incomplete slurry peeling caused by the multi-layered composite structure of the nacelle filter element. The recovered structural components can be used in the production of new filter elements. The solution obtained during the process is easily recoverable and reusable, and is environmentally friendly. The recovered slurry can be directly added to lithium battery production through a specific process, greatly reducing material loss.

[0046] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling and reusing lithium battery slurry from waste filter cartridges, characterized in that the steps include... include: S1. After disassembling the waste filter element, the filter membrane is subjected to low-temperature freezing treatment to obtain agglomerated slurry. S2. Dissolve the agglomerated slurry in a solvent, and then perform ultrasonic treatment, impurity removal treatment and purification treatment in sequence to obtain the slurry. S3. Perform performance testing on the slurry. If the performance does not meet the standard, repeat step S2 until the slurry performance meets the standard, and then qualified recycled slurry is obtained. S4. In the lithium battery slurry dispersion step, the qualified recycled slurry is mixed with the conventional slurry to obtain qualified lithium battery slurry, which can then be discharged for the next step.

2. The method according to claim 1, characterized in that, In step S1, the disassembly process includes: using a crusher to break open the surface layer of the filter element, recovering the filter element shell, and then using a cutting machine to cut open the drainage pipe and the support keel, recovering the drainage pipe and the support layer.

3. The method according to claim 2, characterized in that, The crusher operates at a speed of 500-1000 rpm and has a blade gap of 0.5-2 mm.

4. The method according to claim 1, characterized in that, In step S1, the temperature for low-temperature freezing is -20℃.

5. The method according to claim 1, characterized in that, In step S2, the solvent is N-methylpyrrolidone solvent or water-based solvent.

6. The method according to claim 1, characterized in that, In step S2, the ultrasonic treatment includes: treating with ultrasound at 20-40 kHz at 60-70°C for 30-40 minutes.

7. The method according to claim 1, characterized in that, In step S2, the impurity removal process includes: filtering twice with a 150-mesh sieve, and then filtering once with a 12000GS strong magnetic rod.

8. The method according to claim 1, characterized in that, In step S2, the purification process includes distillation at 170-180℃.

9. The method according to claim 1, characterized in that, In step S3, the performance testing standards are: positive electrode slurry fineness ≤ 10 μm, ICP ≤ 1 ppm; negative electrode slurry fineness 30 μm, ICP ≤ 1 ppm.

10. The method according to claim 1, characterized in that, In step S4, the proportion of qualified recycled slurry in the qualified lithium battery slurry is ≤5%, and the weight of qualified recycled slurry added at one time is ≤50kg.

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