MEI Jian, QIU Lvchao, HUI Yang, ZHAO Zhoufeng, ZOU Junwen
With a retired lithium iron phosphate pouch batteries as an object, the discharge capacity, internal resistance and self-discharge were analyzed, the AC impedance characteristics under different charged state were tested, the charging and discharging characteristics of the different rate and different temperature conditions were researched, the cycle life and calendar life were tested and the security performance of the battery under the abuse condition were researched. The results show that the capacity of the battery in about 85% of the rated capacity, the majority of battery internal resistance between 2.4~3.4 mΩ, after 28 days standing, the capacity retention ratio is above 97%, with the decrease of the SOC, the charge transfer impedance begins to increase gradually. At 25 ℃, it has a good cycle performance, but at 45 ℃, the cycle performance is significantly reduced. At room temperature, it has a good calendar life. When the temperature is 0 ℃ or above, the battery has good rated charging-discharge characteristics. The battery can pass many safety tests and show good safety performance.
