Research on the failure causes of no. 7 alkaline battery packs

　　1. Failure during the production process

　　In the production process, personnel, equipment, raw materials, methods, and the environment are the main factors that affect product quality. The production process of lithium iron phosphate and power batteries is no exception. Personnel and equipment belong to the scope of management. Failure of no. 7 alkaline battery packs caused by impurities in electrode active materials. During the production process, in addition to the production process affecting battery performance, the main factors that cause the failure of lithium iron phosphate power batteries include impurities (including water) in the raw materials and the formation process. Therefore, the purity of the material, the control of environmental humidity, the formation Factors such as method are crucial.

　　2. Failure caused by formation methods on lithium iron batteries

　　The irreversible loss of active lithium ions is first reflected in the lithium ions consumed during the formation of the solid electrolyte interface film. During formation, the composition and thickness of the SEI film formed by low-current charging are uniform, but it is time-consuming; high-current charging will cause more side reactions to occur, causing irreversible lithium ion loss to increase, and the negative electrode interface impedance will also increase.

　　3. Failure of batteries caused by moisture in the production environment

　　In actual production, no. 7 alkaline battery packs will inevitably come into contact with the air, because most of the positive and negative electrode materials are micron or nano-sized particles, and the solvent molecules in the electrolyte contain highly electronegative carbonyl groups and metastable carbon. Carbon double bonds easily absorb moisture from the air. Water molecules react with lithium salts (especially LiPF6) in the electrolyte, which not only decomposes and consumes the electrolyte (decomposes to form PF5), but also produces the acidic substance HF. Both PF5 and HF will destroy the SEI film, and HF will also promote the corrosion of LiFePO4 active materials.

　　4. Failure on hold

　　During the service life of power lithium iron batteries, they are in a state of shelving most of the time. Generally, after a long period of shelving, the battery performance will decline, generally showing an increase in internal resistance, a decrease in voltage, and a decrease in discharge capacity. There are many factors that cause the performance degradation of lithium battery packs, among which temperature, state of charge and time are the most obvious factors.

　　5. Failure during recycling

　　Lithium iron phosphate batteries generally release heat during use, so the influence of temperature is very important. In addition, road conditions, usage patterns, ambient temperature, etc. will all have different effects. During use, the degradation of LiFePO4 electrodes, graphite negative electrodes and the continuous growth of the SEI film cause battery failure to varying degrees.

　　6. Failure during charging and discharging

　　Although LiFePO4 has the best thermal stability compared to other cathode materials under different charging states, overcharging can also cause unsafe risks during use of LiFePO4 power batteries. One of the main causes of failure of lithium iron phosphate batteries under overcharge conditions is internal short circuit caused by lithium dendrites puncturing the separator.

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