Electrochemical Impedance Spectra for Lithium-ion Battery Ageing Considering the Rate of Discharge Ability

Abstract

Abstract The state of health (SOH) of lithium-ion battery is a critical index for the characteristic of the batteries. It is important to evaluate the SOH of lithium-ion cells to avoid dangerous operating conditions and to extend the useful life. The study about the electrochemical impedance characteristics plays an important role for diagnosing the ageing cells. After electrochemical impedance spectra (EIS) tests and the rate of discharge ability tests at various temperatures following cycle life tests, the relation between the electrochemical impedance and the capacity of the ageing batteries is presented in this paper. The batteries experience the same ageing process, but the available capacities at high discharge rate present evident differences while they are similar at low discharge rate. Considering the characteristic demanded in practical applications such as the rate of discharge ability, both impedance and the available capacity of the battery should be taken into account in the evaluation of SOH.