Repair method and application of degenerated electrode of lithium iron phosphate battery

Abstract

The invention relates to a repairing method and application of a degraded electrode of a lithium iron phosphate battery, and belongs to the technical field of lithium ion battery recycling, the repairing method comprises the following steps: respectively taking lithium acetate, dimethyl sulfoxide and dimethyl ammonia borane, and uniformly stirring to obtain a re-lithiation reaction solution for later use; the method comprises the following steps: providing a lithium iron phosphate battery positive electrode material, mixing the lithium iron phosphate battery positive electrode material in a re-lithiation reaction solution, stirring for 1-3 hours at normal temperature and normal pressure, then carrying out solid-liquid separation to obtain a solid-phase positive electrode material, washing the solid-phase positive electrode material with dimethyl sulfoxide and ethanol in sequence, and carrying out drying treatment to obtain the regenerated LiFePO material. The method for repairing the degenerated electrode of the lithium iron phosphate battery has the characteristics of simplicity in operation, low cost and environment friendliness, and the capacity retention ratio of the prepared regenerated LiFePOmaterial reaches 90% after 100 times of circulation under 1C multiplying power.

Description

Technical Field

[0001] The invention relates to the technical field of coal tar processing, and in particular to a novel high-temperature coal tar fraction separation process and system using vacuum distillation and supercritical extraction processes. Background Art

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

[0003] At present, traditional recycling technologies include pyrometallurgy and hydrometallurgy, which have problems such as high energy consumption, large amount of reagents used, and serious environmental impact. Direct regeneration technology can restore the performance of electrodes under mild conditions by replenishing lithium ions and repairing the electrode structure. It is an important direction for green recycling. However, in the existing technology, the operating conditions of the direct regeneration method include high temperature and high pressure, complex equipment and high cost, which cannot be applied on a large scale. Therefore, it is urgent to develop a low-cost, low-energy, green and environmentally friendly lithium iron phosphate battery regeneration technology. Summary of the invention

[0004] The purpose of the present invention is to provide a method and application for repairing degraded electrodes of lithium iron phosphate batteries, by performing precise re-lithiation reaction at normal temperature and pressure, thereby restoring the electrochemical properties of electrode materials, extending the battery life, and promoting the green recycling and resource utilization of waste batteries.

[0005] The present invention provides a method for repairing a degraded electrode of a lithium iron phosphate battery, which adopts the following technical solution: A method for repairing a degraded electrode of a lithium iron phosphate battery comprises the following steps: S1, respectively taking lithium acetate, dimethyl salinityle and dimethylamine borane, dissolving lithium acetate in dimethyl salinityle, then adding dimethylamine borane, stirring evenly to obtain a relithiation reaction solution for standby use; S2. Provide positive electrode materials for lithium iron phosphate batteries; S3, mixing the lithium iron phosphate battery positive electrode material prepared in step S2 with the relithiation reaction solution prepared in step S1, stirring for 1-3 hours and then performing solid-liquid separation to obtain a solid phase positive electrode material; S4. Use dimethyl sulfide and ethanol to wash the solid phase positive electrode material obtained in step S3 in turn, and obtain the regenerated LiFePO4 material after drying.

[0006] Preferably, the molar ratio of dimethyl sulfide, dimethylamine borane and lithium iron phosphate battery positive electrode material in the relithiation reaction solution in step S3 is 2:1:1.

[0007] Preferably, the amount of lithium acetate in the relithiation reaction solution in step S3 is 10-30% of the positive electrode material of the lithium iron phosphate battery.

[0008] Preferably, in step S3, stirring is performed at room temperature, which is 25-30° C., and the stirring speed is set to 300 rpm.

[0009] Preferably, the drying process in step S4 includes placing the solid-phase positive electrode material obtained in step S3 in a vacuum drying oven, setting the temperature of the vacuum drying oven to 60-80° C. and the drying time to 12 hours.

[0010] Preferably, the capacity retention rate of the regenerated LiFePO4 material in step S4 is ≥90% after 100 cycles at a rate of 1C.

[0011] The present invention also provides an application of a method for repairing a degraded electrode of a lithium iron phosphate battery in lithium ion battery recycling.

[0012] In summary, the present invention includes the following beneficial technical effects: 1. In the present application, lithium acetate is used as a lithium ion donor to provide an efficient and stable lithium source during the reaction process. Its complete dissolution in dimethyl samarium can ensure the 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 can reduce Fe³⁺ in the lithium iron phosphate electrode material to electrochemically active Fe²⁺ during the reaction, thereby restoring the electrochemical properties of the positive electrode material. The mild reducing ability of dimethylamine borane is suitable for realizing the reaction at room temperature and pressure, avoiding the need for high temperature and high pressure conditions.

[0013] 2. The capacity retention rate of the regenerated LiFePO4 material prepared in this application is ≥90% after 100 cycles at a 1C rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of a process of repairing a degraded electrode of a lithium iron phosphate battery according to the present application; Figure 2 This is a discharge cycle comparison chart of the regenerated LiFePO4 material prepared in this application and the degraded electrode of the waste lithium iron phosphate battery. DETAILED DESCRIPTION

[0015] The following is combined with Figure 1 The present invention is further described in detail with reference to the accompanying drawings and examples.

[0016] Example 1 A method for repairing a degraded electrode of a lithium iron phosphate battery, referring to Figure 1 , including the following steps: 1) Take lithium acetate, dimethyl samarium and dimethylamine borane respectively, dissolve lithium acetate in dimethyl samarium, add dimethylamine borane, stir evenly to obtain a relithiation reaction solution for later use; 2) Provide positive electrode materials for lithium iron phosphate batteries; 3) Mix 2 g of the lithium iron phosphate battery positive electrode material prepared in step 2) with 50 mL of the relithiation reaction solution prepared in step S1, stir for 1-3 h at room temperature of 25-30° C., set the stirring speed to 300 rpm, and then perform solid-liquid separation to obtain a solid phase positive electrode material; 4) The solid-phase cathode material obtained in step S3 is cleaned with dimethyl sulfide at least three times, and then the solid-phase cathode material is cleaned with ethanol. After cleaning, the solid-phase cathode material is placed in a vacuum drying oven at a temperature of 60-80° C. and dried for 12 hours to obtain a regenerated LiFePO4 material; Wherein, the molar ratio of dimethyl samarium, dimethylamine borane and lithium iron phosphate battery positive electrode material in the relithiation reaction solution in step 3) 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 positive electrode material; The method for repairing degraded electrodes of lithium iron phosphate batteries in this embodiment 1 is applied to lithium-ion battery recycling.

[0017] Comparative Example 1 A method for repairing a degraded electrode of a lithium iron phosphate battery, which is different from Example 1 in that the lithium acetate in step 1) is replaced by an equal weight portion of dimethyl sulfide, and the remaining steps are the same as in Example 1.

[0018] Comparative Example 2 A method for repairing a degraded electrode of a lithium iron phosphate battery, which is different from Example 1 in that the dimethyl sulfoxide salt in step 1) is replaced by an equal weight portion of lithium acetate, and the remaining steps are the same as in Example 1.

[0019] Comparative Example 3 A method for repairing a degraded electrode of a lithium iron phosphate battery, which is different from Example 1 in that the dimethylamine borane in step 1) is replaced with an equal weight portion of dimethyl sulfoxide, and the remaining steps are the same as Example 1.

[0020] Comparative Example 4 A method for repairing a degraded electrode of a lithium iron phosphate battery uses a high-temperature roasting method or a hydrometallurgical method to repair the degraded electrode of the lithium iron phosphate battery.

[0021] Comparative Example 5 A method for repairing a degraded electrode of a lithium iron phosphate battery, which is different from Example 1 in that in step 3), the positive electrode material of the lithium iron phosphate battery and the relithiation reaction solution react in a high temperature and high pressure environment, and the remaining steps are the same as Example 1.

[0022] Performance test results The regenerated LiFePO4 material prepared in Example 1 was used to form a button cell. The test results showed that the initial discharge capacity reached 143 mAh / g (0.1C rate); after 100 cycles at 1C rate, the capacity retention rate was as high as 90%. Figure 2 , Figure 2 This is a discharge cycle comparison diagram of the regenerated LiFePO4 material prepared in the present application and the degraded electrode of the waste lithium iron phosphate battery. The performance of the regenerated LiFePO4 material prepared in the present application is greatly improved, and the performance is close to that of new materials.

[0023] No significant lithium ion embedding was detected in the regenerated LiFePO4 material prepared in Comparative Example 1, and the capacity recovery rate of the positive electrode material was only about 20%; in the regenerated LiFePO4 material prepared in Comparative Example 2, the electrochemical performance of the positive electrode material was almost not restored 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 prepared in Comparative Example 3 was less than 30%, because the Fe³⁺ of the positive electrode material could not be reduced to Fe²⁺; the capacity recovery rate of the regenerated 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, and the waste liquid produced caused greater environmental pollution; the regenerated LiFePO4 material prepared in Comparative Example 5 was costly and had the phenomenon of crystal structure damage at high temperatures.

[0024] In summary, the repair method of the degraded electrode of the lithium iron phosphate battery in this application has the characteristics of high material recovery rate, green environmental protection, and low operating cost. The capacity and cycle life of the regenerated LiFePO4 material after relithiation are close to the level of new materials; no strong acid, strong alkali or high-temperature roasting is required, no waste liquid is generated, and it meets environmental protection requirements; the reaction is completed at room temperature and pressure, the equipment requirements are simple, and it is suitable for large-scale promotion The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for repairing a degraded electrode of a lithium iron phosphate battery, characterized in that: The following steps are involved: S1, respectively taking lithium acetate, dimethyl salinityle and dimethylamine borane, dissolving lithium acetate in dimethyl salinityle, then adding dimethylamine borane, stirring evenly to obtain a relithiation reaction solution for standby use; S2. Provide positive electrode materials for lithium iron phosphate batteries; S3, mixing the lithium iron phosphate battery positive electrode material prepared in step S2 with the relithiation reaction solution prepared in step S1, stirring for 1-3 hours and then performing solid-liquid separation to obtain a solid phase positive electrode material; S4. The solid phase positive electrode material obtained in step S3 is washed with dimethyl sulfide and ethanol in turn, and the regenerated LiFePO4 material is obtained after drying.

2. The method for repairing a degraded electrode of a lithium iron phosphate battery according to claim 1, characterized in that: The molar ratio of dimethyl sulfide, dimethylamine borane and lithium iron phosphate battery positive electrode material in the relithiation reaction solution in step S3 is 2:1:

1.

3. The method for repairing a degraded electrode of 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 positive electrode material of the lithium iron phosphate battery.

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

5. The method for repairing a degraded electrode of a lithium iron phosphate battery according to claim 1, characterized in that: The drying process in step S4 includes placing the solid phase positive electrode material obtained in step S3 in a vacuum drying oven, setting the temperature of the vacuum drying oven to 60-80° C. and the drying time to 12 hours.

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

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

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