Abstract:

The influence of copper foil microscopic appearance on Li-ion battery performance was discussed. Scanning electron microscope (SEM) results showed that there was a spot-like flaw on the defective copper film. Soft-package battery was prepared with the defective and qualified copper foils, respectively. The batteries' performance was evaluated, including electrochemical impedance spectra (EIS) analysis,discharging at both low temperature and room temperature, and cycle performance. It has been concluded from the EIS simulation result that the defective copper foil could have a severe influence on ohm impedance values, which are 31.95 mΩ and 11.78 mΩ for defective and qualified copper film, respectively. Besides, the low-temperature discharge and cycle performance of defective copper film batteries are inferior to that of the qualified copper film battery. It was also found from the disassembled battery that the anode electrode coated by the defective copper foil has poor adherence. The phenomenon also happened in the freshly prepared anode electrode.

Key words: copper foil, Li-ion power battery, low temperature discharge