Deterioration analysis in cycling test at high temperature of 60°C for Li-ion cells using SiO anode

We carried out a deterioration analysis in Li-ion cells using SiO anode at high temperature, i.e., 60°C. The capacity retention at the upper cutoff voltage (UCV) of 4.0, 4.1, and 4.2 V after 400 cycles was about 80, 80, and 20%, respectively. The cell deterioration depended strongly on the upper cutoff voltage and proceeded drastically at 4.2 V. This was because the internal resistance of cell increased by the decomposition of the electrolytic solution during cycles. From depth profile of XPS on the anode, the thick layer containing Li and F has been formed only for UCV = 4.2 V, implying that the electrolyte of LiPF6 is enough to break down carbonate electrolyte at 60°C. Therefore, we found that the optimization of the threshold of UCV for high temperature need to attain the good cycle performance at high temperature in a Li-ion battery using a SiO anode.