A method for repairing degraded electrodes of lithium iron phosphate batteries and applications thereof

Abstract

The application relates to a lithium iron phosphate battery degraded electrode repairing method and application, and belongs to the lithium ion battery recycling technical field, and comprises the following steps: respectively taking lithium acetate, dimethyl sulfoxide and dimethyl borane amine, stirring uniformly to obtain a re-lithiation reaction solution for standby; providing a lithium iron phosphate battery positive electrode material, mixing in the re-lithiation reaction solution, stirring for 1-3 hours under normal temperature and normal pressure, then carrying out solid-liquid separation to obtain a solid positive electrode material, sequentially cleaning the solid positive electrode material by using dimethyl sulfoxide and ethanol, and carrying out drying treatment to obtain regenerated LiFePO4 material. The lithium iron phosphate battery degraded electrode repairing method has the characteristics of simple operation, low cost and green environmental protection, and the capacity retention rate of the prepared regenerated LiFePO4 material reaches 90% after 100 cycles under 1C rate.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, and in particular to a method and application for repairing degraded electrodes of lithium iron phosphate batteries. Background Technology

[0002] With the widespread use of lithium-ion batteries in electric vehicles, energy storage devices, and other fields, the number of used batteries has increased dramatically. Lithium iron phosphate batteries are widely used due to their high safety and long lifespan, but if retired batteries are not properly recycled, they will impose a significant burden on the environment.

[0003] Currently, traditional recycling technologies, including pyrometallurgy and hydrometallurgy, suffer from high energy consumption, large reagent usage, and severe environmental impact. Direct regeneration technology, by replenishing lithium ions and repairing electrode structure, can restore electrode performance under mild conditions, representing an important direction for green recycling. However, existing direct regeneration methods are hampered by high temperature and pressure, complex equipment, and high costs, hindering large-scale application. Therefore, there is an urgent need to develop a low-cost, low-energy, and environmentally friendly lithium iron phosphate battery regeneration technology. Summary of the Invention

[0004] The purpose of this invention is to provide a method and application for repairing degraded electrodes of lithium iron phosphate batteries. By carrying out a precise relithiation reaction at room temperature and pressure, the electrochemical performance of the electrode material is restored, the battery life is extended, and the green recycling and resource utilization of waste batteries are promoted.

[0005] The present invention provides a method for repairing degraded electrodes in lithium iron phosphate batteries, which adopts the following technical solution:

[0006] A method for repairing degraded electrodes in lithium iron phosphate batteries includes the following steps:

[0007] S1. Take lithium acetate, dimethyl sulfoxide and dimethylaminoborane respectively. Dissolve lithium acetate in dimethyl sulfoxide, then add dimethylaminoborane and stir until homogeneous to obtain a relithiation reaction solution for later use.

[0008] S2, providing cathode materials for lithium iron phosphate batteries;

[0009] S3. The lithium iron phosphate battery cathode material prepared in step S2 is mixed in the relithiation reaction solution prepared in step S1, stirred for 1-3 hours and then separated into solid and liquid phases to obtain solid cathode material.

[0010] S4. The solid-phase cathode material obtained in step S3 is washed sequentially with dimethyl sulfoxide and ethanol, and then dried to obtain regenerated LiFePO4 material.

[0011] Preferably, in step S3, the molar ratio of dimethyl sulfoxide, dimethylaminoborane, and lithium iron phosphate battery cathode material in the relithiation reaction solution is 2:1:1.

[0012] Preferably, the amount of lithium acetate in the relithiation reaction solution in step S3 is 10-30% of the lithium iron phosphate battery cathode material.

[0013] Preferably, in step S3, stirring is performed at room temperature (25-30°C) and the stirring speed is set to 300 rpm.

[0014] Preferably, the drying process in step S4 includes placing the solid-phase cathode material obtained in step S3 into a vacuum drying oven, setting the temperature of the vacuum drying oven to 60-80℃, and the drying time to 12h.

[0015] Preferably, the regenerated LiFePO4 material in step S4 retains ≥90% of its capacity after 100 cycles at a 1C rate.

[0016] The present invention also provides an application of a method for repairing degraded electrodes of lithium iron phosphate batteries in lithium-ion battery recycling.

[0017] In summary, the present invention has the following beneficial technical effects:

[0018] 1. In this application, lithium acetate serves as a lithium-ion donor, providing an efficient and stable lithium source during the reaction. Its complete dissolution in dimethyl sulfoxide ensures a uniform distribution of lithium ions, thereby promoting the rapid embedding of lithium ions into the lattice of the degraded electrode material and restoring its lithium-ion storage capacity. Dimethylamine borane, during the reaction, can remove Fe from the lithium iron phosphate electrode material... 3+ Reduced to electrochemically active Fe 2+ This restores the electrochemical performance of the cathode material, and the mild reducing ability of dimethylamine borane is suitable for the reaction to be carried out at room temperature and pressure, avoiding the need for high temperature and high pressure conditions.

[0019] 2. The recycled LiFePO4 material prepared in this application retains ≥90% capacity after 100 cycles at 1C rate. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a method for repairing degraded electrodes in a lithium iron phosphate battery according to this application.

[0021] Figure 2 This is a comparison diagram of the discharge cycle of the recycled LiFePO4 material prepared in this application and the degraded electrode of a waste lithium iron phosphate battery. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1-2 The present invention will be further described in detail with reference to the embodiments. Example

[0023] A method for repairing degraded electrodes in lithium iron phosphate batteries, referring to... Figure 1 This includes the following steps:

[0024] 1) Take lithium acetate, dimethyl sulfoxide and dimethylaminoborane respectively. Dissolve lithium acetate in dimethyl sulfoxide, then add dimethylaminoborane and stir until homogeneous to obtain a relithiation reaction solution for later use.

[0025] 2) Provide cathode materials for lithium iron phosphate batteries;

[0026] 3) Mix 2g of lithium iron phosphate battery cathode material prepared in step 2) into 50mL of relithiation reaction solution prepared in step S1, stir for 1-3h at room temperature (25-30℃) with a stirring speed of 300rpm, and then perform solid-liquid separation to obtain solid cathode material.

[0027] 4) The solid cathode material obtained in step S3 is cleaned with dimethyl sulfoxide. The solid cathode material is cleaned with dimethyl sulfoxide at least three times. Then, the solid cathode material is cleaned with ethanol. After cleaning, it is placed in a vacuum drying oven at 60-80℃ and dried for 12 hours to obtain regenerated LiFePO4 material.

[0028] In step 3), the molar ratio of dimethyl sulfoxide, dimethylaminoborane, and lithium iron phosphate battery cathode material in the relithiation reaction solution is 2:1:1; the amount of lithium acetate in the relithiation reaction solution in step 3) is 10-30% of the lithium iron phosphate battery cathode material.

[0029] The method for repairing degraded electrodes in lithium iron phosphate batteries described in Example 1 is applied to lithium-ion battery recycling.

[0030] Comparative Example 1

[0031] A method for repairing degraded electrodes of lithium iron phosphate batteries, which differs from Example 1 in that lithium acetate in step 1) is replaced with an equal part by weight of dimethyl sulfoxide, while the remaining steps are the same as in Example 1.

[0032] Comparative Example 2

[0033] A method for repairing degraded electrodes of lithium iron phosphate batteries, which differs from Example 1 in that the dimethyl sulfoxide in step 1) is replaced with an equal part by weight of lithium acetate, while the remaining steps are the same as in Example 1.

[0034] Comparative Example 3

[0035] A method for repairing degraded electrodes of lithium iron phosphate batteries, which differs from Example 1 in that the dimethylamine borane in step 1) is replaced with an equal part by weight of dimethyl sulfoxide, while the remaining steps are the same as in Example 1.

[0036] Comparative Example 4

[0037] A method for repairing degraded electrodes of lithium iron phosphate batteries, using high-temperature calcination or hydrometallurgical methods.

[0038] Comparative Example 5

[0039] A method for repairing degraded electrodes of lithium iron phosphate batteries, which differs from Example 1 in that, in step 3), the lithium iron phosphate battery cathode material and the relithiation reaction solution react in a high temperature and high pressure environment, while the remaining steps are the same as in Example 1.

[0040] Performance test results

[0041] A coin cell was constructed using the recycled LiFePO4 material obtained in Example 1. Test results showed an initial discharge capacity of 143 mAh / g (0.1C rate); after 100 cycles at 1C rate, the capacity retention was as high as 90%. (Refer to...) Figure 2 , Figure 2 The diagram shows a comparison of the discharge cycle performance of the recycled LiFePO4 material prepared in this application and the degraded electrode of a waste lithium iron phosphate battery. The performance of the recycled LiFePO4 material prepared in this application is greatly improved and is close to that of the new material.

[0042] In Comparative Example 1, no significant lithium-ion intercalation was detected in the regenerated LiFePO4 material, and the capacity recovery rate of the cathode material was only about 20%. In Comparative Example 2, the electrochemical performance of the cathode material was almost not recovered because the aqueous solution could not effectively disperse the electrode material and the impurity removal effect was poor. The capacity recovery rate of the regenerated LiFePO4 material in Comparative Example 3 was less than 30%, because the Fe in the cathode material was... 3+ Unable to be reduced to Fe 2+ The capacity recovery rate of the recycled LiFePO4 material prepared in Comparative Example 4 reached 85%, but the operation required high-temperature and high-pressure equipment, and the energy consumption was significantly higher than that of the present invention. At the same time, the waste liquid generated caused significant environmental pollution. The recycled LiFePO4 material prepared in Comparative Example 5 was expensive, and crystal structure damage occurred at high temperatures.

[0043] In summary, the method for repairing degraded electrodes in lithium iron phosphate batteries presented in this application features high material recovery rate, environmental friendliness, and low operating costs. The capacity and cycle life of the regenerated LiFePO4 material after relithiation are close to those of virgin materials. It eliminates the need for strong acids, strong alkalis, or high-temperature calcination, producing no waste liquid and meeting environmental protection requirements. The reaction is completed at room temperature and pressure, requiring simple equipment and making it suitable for large-scale deployment.

[0044] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for repairing degraded electrodes in a lithium iron phosphate battery, characterized in that, Includes the following steps: S1. Take lithium acetate, dimethyl sulfoxide and dimethylaminoborane respectively. Dissolve lithium acetate in dimethyl sulfoxide, then add dimethylaminoborane and stir until homogeneous to obtain a relithiation reaction solution for later use. S2, providing cathode materials for lithium iron phosphate batteries; S3. The lithium iron phosphate battery cathode material prepared in step S2 is mixed in the relithiation reaction solution prepared in step S1, stirred for 1-3 hours and then separated into solid and liquid phases to obtain solid cathode material. S4. The solid-phase cathode material obtained in step S3 is sequentially cleaned with dimethyl sulfoxide and ethanol, and then dried to obtain regenerated LiFePO4 material.

2. The method for repairing degraded electrodes in a lithium iron phosphate battery according to claim 1, characterized in that, In step S3, the molar ratio of dimethyl sulfoxide, dimethylaminoborane, and lithium iron phosphate battery cathode material in the relithiation reaction solution is 2:1:

1.

3. The method for repairing degraded electrodes in a lithium iron phosphate battery according to claim 1, characterized in that, The amount of lithium acetate in the relithiation reaction solution in step S3 is 10-30% of the lithium iron phosphate battery cathode material.

4. The method for repairing degraded electrodes in a lithium iron phosphate battery according to claim 1, characterized in that, In step S3, stirring is performed at room temperature with a stirring speed of 300 rpm.

5. A method for repairing degraded electrodes in a lithium iron phosphate battery according to claim 1, characterized in that, The drying process in step S4 includes placing the solid cathode material obtained in step S3 into a vacuum drying oven, setting the temperature of the vacuum drying oven to 60-80℃, and the drying time to 12h.

6. The method for repairing degraded electrodes in a lithium iron phosphate battery according to claim 1, characterized in that, The regenerated LiFePO4 material in step S4 retains ≥90% of its capacity after 100 cycles at 1C rate.

7. The application of the method for repairing degraded electrodes of lithium iron phosphate batteries according to any one of claims 1-6 in lithium-ion battery recycling.

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