Effect of pretreatment process on performance of lithium iron phosphate battery

　　Lithium iron phosphate batteries have become the focus of many battery companies and automobile manufacturing companies due to their good safety and comprehensive electrochemical properties. If there are trace amounts of moisture and free acid in the organic electrolyte of a lithium-ion battery, it will react with the lithium salt in the electrolyte to form fluoride and deposit on the surface of the negative electrode. The existence of this deposit will play an important role in the formation of the SEI film. .

　　Lithium iron phosphate batteries have become the focus of many battery companies and automobile manufacturing companies due to their good safety and comprehensive electrochemical properties. If there are trace amounts of moisture and free acid in the organic electrolyte of a lithium-ion battery, it will react with the lithium salt in the electrolyte to form fluoride and deposit on the surface of the negative electrode. The existence of this deposit will play an important role in the formation of the SEI film. .

　　However, excessive water and acid content will not only cause the decomposition of the lithium salt LiPF6, but also damage the SEI film. The reaction rate between LiPF6 and water increases as the temperature increases. The reaction rate constant at 40°C is 3 to 4 times that at 20°C, and at 60°C it increases to 8 to 12 times that at 20°C. The decomposition of lithium salt and the generation of HF gas will cause the battery cycle life to decay, cause serious gas swelling, and pose certain safety issues.

　　This article focuses on the lithium iron phosphate 20Ah power battery with high moisture content and difficult to dry. It uses the SEI film-forming reaction that occurs on the electrode surface during the first charge to remove the moisture inside the battery, and studies the effect of different pretreatment processes on battery moisture removal. Investigate the effects of preformation process and high-temperature storage on battery performance (capacity, pole piece status, battery thickness, and internal resistance).

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