温度对磷酸铁锂电池化成效果的影响

Effect of Temperature on the Formation Result of Lithium Iron Phosphate Battery

为优化磷酸铁锂电池化成工艺参数,对比了25℃和20℃2个温度对化成效果的影响,从电解液黏度及电导率、容量-电压微分曲线、电极片和卷芯厚度、负极形貌及元素成分、负极粉料热稳定性方面进行了对比。结果表明:化成温度降低,化成效果较差,电解液黏度增大35.2%,电导率降低7.1%,容量-电压微分曲线峰位1降低,峰位2升高,负极片厚度增加12.9%,卷芯厚度增加3.4%,负极片表面有明显的颗粒凸起,出现大量的氧元素,且从箔材侧到隔膜侧含量递增,出现明显的放热峰,初步认为是受负极成膜时电解液去溶剂化困难导致锂离子与溶剂共嵌入石墨的影响。采用对卷芯施加力的方法可改善化成温度降低引起的化成不良。该结果对于商业生产中化成工艺参数的设定、过程控制、失效分析等方面具有重要指导意义。

In order to optimize the formation process parameters of lithium iron phosphate battery,the effects of 25℃and20℃on the formation result were compared,the viscosity and conductivity of electrolyte,capacity-voltage differential curve,thickness of negative electrode and jelly roll,morphology and element composition of negative electrode,thermal stability of negative powders were analyzed.The results showed that the viscosity and conductivity of electrolyte increased by 35.2%and decreased by 7.1%,respectively,the peak 1 of capacity-voltage differential curve decreased,the peak 2 increased,and the thickness of negative electrode increased by 12.9%,the thickness of the jelly roll increased by 3.4%,the surface of the negative electrode had obvious particle bulge,a large amount of oxygen element appeared,and the content of oxygen increased from the foil side to the separator side,and an obvious exothermic peak appeared,it is believed preliminarily that the co-intercalation of lithium ion and solvents into graphite is caused by the difficulty of electrolyte desolvation during the formation.The formation defect caused by low formation temperature could be improved by applying force on the jelly roll.The results have important guiding significance for the setting of process parameters,process control and failure analysis in commercial production.