化成充电SOC对软包磷酸铁锂电池性能的影响

Influence of the Formation SOC on the Performance of Pouch Lithium Ion Battery

在锂离子电池生产制造中,化成是最重要的工序之一。化成工艺决定了电池内部固态电解质膜的质量,进而影响到电池各项终端性能。然而,电池化成后充电到多少荷电状态(SOC)性能最佳,一直未能有较为统一的结论。本文通过实验研究了不同化成充电SOC对软包磷酸铁锂锂离子电池的容量、首次库伦效率、高低温放电性能、倍率充放电性能、循环性能的影响。不同组的实验电池化成SOC分别采用10%、40%、70%、100%。结果表明,化成SOC越高,电池首次库伦效率及容量越低;化成SOC为100%时,电池高低温放电性能最佳;化成SOC为70%时,电池倍率充电及倍率放电性能均最佳;化成SOC为70%或100%时,电池循环寿命最佳。因此,化成充电SOC为70%或100%时电池综合性能最佳。其中化成充电SOC为70%时,倍率充放电性能更好且成本更低;化成充电SOC为100%时,高低温充放电性能更好。

Formation is one of the most important processes in lithium ion battery production. Formation process determines the quality of solid electrolyte interface(SEI), and then affects the terminal performance of the battery. However, there is not a relatively unified conclusion that which state of charge(SOC) after formation process can lead to the best performance. In this paper, the effects of different charging SOC on the battery capacity, first Coulomb efficiency, high and low temperature discharge performance, rate charge and discharge performance, and cycle performance of the pouch lithium iron phosphate battery were studied experimentally. Formation SOCs of different groups of experimental batteries were set to 10 %, 40 %, 70 % and 100 % respectively. Experimental results show that higher formation SOC leads to a lower first Coulomb efficiency and battery capacity. The performance of high and low temperature discharge is the best when the formation SOC is 100 %. The performance of rate charge and discharge is the best when the formation SOC is 70 %. The cycle life of the battery is longer when the formation SOC is 70 % or 100 %. Therefore, the recommended formation SOC is 70 % or 100 % for the comprehensive performance of the battery. To maintain higher rate performance while reducing battery cost, SOC can be set to 70 %. To maintain higher discharge performance at high and low temperature, SOC can be set to 70 %.