LiFePO4极片真空干燥特性及动力学

Vacuum Drying of Flexible LiFePO4 Electrode for Lithium Ion Battery:An Experimental Study

探讨了不同温度、不同真空度对LiFePO4极片材料烘烤水分的影响,并对LiFePO4极片材料真空干燥实验数据进行线性回归分析,得到LiFePO4极片材料水分扩散系数以及活化能等动力学参数。结果表明:烘烤系统真空度越高,温度越高,极片的水分比越低,干燥效果越好。烘烤温度越低,系统真空度差异对极片干燥效果有明显的区别。在实验条件下LiFePO4极片材料水分扩散系数处在(1.11~1.86)×10^-9 m^2/s,真空度越高,温度越高,水分扩散系数越大,水分的蒸发快慢受制于水分的扩散迁移速度。LiFePO4极片材料水分活化能在9.70~19.83 kJ/mol,真空度越高,水分活化能越低。应用Fick扩散定律以及Arrhenius方程,薄层干燥模型Henderson(MR=Aexp(-zt))描述LiFePO4极片水分迁移规律取得良好拟合效果,对预测LiFePO4极片干燥过程具有重要指导意义。

We reported the vacuum drying of flexible Li-ion battery electrode of LiFePO4 coatings,deposited on Al-foil by spray painting.The influence of the drying pressure and temperature on moisture evaporation-rate of LiFePO4 coating electrode was investigated.The results show that the pressure and temperature had a major impact.To be specific,the moisture evaporation-rate increased with an increase of temperature and/or a decrease of pressure,because of the significant increase of moisture diffusion-coefficient of LiFePO4 electrode,estimated to be in 1.11×10^-9 to 1.86×10^-9 m^2/s range.Depending on the pressure,the moisture activation energy was in 9.70~19.83 kJ/mol range.Henderson model was found to well describe the vacuum drying of LiFePO4 coating.We suggest that the vacuum drying of LiFePO4 electrode be of some technological interest in industrial production of Li-ion battery.