Study of rate dependence of impedance of lithium ion batteries

Impedance as one of the most important parameters of a battery has been studied a lot. While most works only consider the impedance is related with the state-of-charge (SOC), very little attention has been put upon the rate dependence of impedance. In this work, the impedance of a battery has been considered to be dependent on the SOC and the charging or discharging rate. A series of charging and discharging tests are proposed to extract the impedance values based on an equivalent circuit model without electrochemical impedance spectroscopic measurement. The rate dependence of impedance has been analysed in detail, and the results show that it cannot be neglected for some applications which involve charging or discharging at different rates if high accuracy is required.