The Operation Dependence of C - N Fatigue for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) fatigue in repeated service, and their cycle-life, in resemblance to most materials subject to cyclic loading, scatters over a broad range. The dependence of critical fatigue parameters on ambient temperature and charging or discharging rate, along with the scattering nature of cycle-life is of practical significance. Through large-scale experimental investigations, it is shown how both temperatures and charging-discharging rates may influence critical parameters in the C - N fatigue dependence for LIBs. The cycle-life N of a battery subject to an average charging rate C follows C = c(0) (T)N-b(D), where c(0) varies with temperature T and b is a function of the discharging rate D. It is further shown that the cycle-life of LIBs follows a lognormal distribution. The revealed cycle-life distribution of LIBs and their fatigue law enable the construction of a probabilistic C - N model, which can be used to quantify the fatigue failure probability in LIBs. Results reported here are of compelling importance for the life-span evaluation and safety design of large-scale battery packing in electric vehicles and energy storage where tens of hundreds of batteries working in concert is desired.