Analysis on cycle degradation of lithium-ion secondary batteries by applying current interruption methods

The correlation between the current interrupted transient response and the cycle deterioration of a commercially available lithium-ion secondary battery have been analyzed by applying a two-stage distributed constant circuit. It was better to take cycle deterioration by elapsed time rather than the charge/discharge cycles. The capacity deterioration rate depends on the upper limit of SOC. The capacity deterioration rate of SOC = 0-70 % and 0-90 % was similar but increased at SOC = 0-100 %. In the transient response analysis, the iR jump and the overvoltage at the composite electrode was similar for SOC = 50 % charge, 100 % charge, and 50 % discharge, but the iR jump at SOC = 0 % discharge was 1.7 times larger, and the overvoltage of the composite electrode was about 6 times larger. Contrary to the hypothesis that the overvoltage at both of the composite electrode and of iR jump increases with the capacity deterioration, only the conductance as the reciprocal of the iR jump showed good linear correlation to deterioration. The conductance of iR jump became the half of the initial value, the capacity loss became 25 %. On the other hand, there was no correlation with the overvoltage and conductance of the composite electrode. From these results, it was concluded that it was recommended to adopt the conductance of iR jump as the control item of BMS.