Performance mutation mechanism and parametric characterization method of high-capacity lithium-ion battery

The mutation of power battery performance brings serious reliability and safety problems, and has developed into an urgent common issue of electric vehicle power battery running and echelon utilization. It is essential to investigate the performance mutation mechanism and parametric characterization method of lithium-ion batteries. In this paper, the mutation effect of battery performance under state of charge (SOC) interval and temperature cyclic conditions is discovered. Moreover, thermodynamic investigation method based on the half-cell potential synthesis is implemented to explore the evolution of equilibrium potential. Furthermore, the dynamic investigation method based on distribution of relaxation time (DRT) and equivalent circuit model (ECM) are introduced to describe the impedance characteristics of batteries. Eventually, the mechanism of battery performance mutation is revealed and the parameters characterizing the mutation are extracted. The mutation effect contains inducing point and crossing point, and is caused by the mutation of the negative active material. In addition, the charge transfer impedance and diffusion impedance in the SOC range of 10%–20% are particularly sensitive to the mutation, and a feasible method for identifying mutant battery and aging path based on the extracted parameters is proposed. It provides superintendence for the safe and economical application of power batteries.