关键词: 水分, 磷酸亚铁锂, 软包电池, 循环性能

Abstract:

Through different dry conditions and measuring by moisture test instrument, cathode pole pieces with different water contents of 0.3‰ ~ 0.7‰ were obtained to prepare lithium-ion batteries. Cycling performance and high rate performance at 1C ~ 5C discharge rates were tested. Moreover, ASR performances of LiFePO4 base lithium-ion batteries after 200 cycles with different water contents were investigated by EIS. The results showed that the cycle performance and rate performance were closely related to the water content of the electrode. When the water content went up to 0.6‰ the cycle stability and rate performance fell. Meanwhile, the internal resistance and the electrochemical reaction impedance increased after 200 cycles. The cells after running 200 cycles were dismantled to obtain the powder material which was studied by laser particle size analyzer, XRD and SEM to research the microstructure. The results revealed that when the water content exceeded 0.6‰ the obvious particle fracture phenomenon appeared. The XRD data indicated that the position of the main diffraction peak kept nearly the same and the crystal phase of the cathode material remained unchanged.

Key words: water content, lithium iron phosphate, full cell, cycle performance