Fatigue damage approach applied to Li-ion batteries ageing characterization

Abstract Reliability of energy storage devices is one of the foremost concerns in electric vehicles (EVs) development. Battery ageing, i.e. the degradation of battery energy and power, depends mainly on time, on the environmental conditions and on the in-use solicitations endured by the storage system. In case of EV, the heavy dependence of the battery use with the car performance, the driving cycles, and the weather conditions make the battery life prediction an intricate issue. Mechanical physicists have developed a quick and exhaustive methodology to diagnose reliability of complex structures enduring complex loads. This “fatigue” approach expresses the performance fading due to a complex load through the evolution corresponding to basic ones. Thus, a state of health variable named “damage” binds the load history and ageing. The battery ageing study described here consists in applying this mechanical approach to electrochemical systems by connecting the ageing factors with the battery characteristics evolutions. In that way, a specific “fatigue” test protocol has been established. This experimental confrontation has led to distinguishing calendar from cycling ageing mechanisms.