State of charge-dependent failure prediction model for cylindrical lithium-ion batteries under mechanical abuse

Based on the previous research, the parameters of the equivalent mechanical model are associated with state of charge, thus, the model can simulate the mechanical behavior of cylindrical lithium-ion batteries under continuous state of charge with simulation software. The comparison results show that the average fitting error of the equivalent mechanical model under different state-of-charge is less than 3.91% and the simulation error for failure displacement is less than 4%. Apart from that, the equivalent spring stiffness of the equivalent mechanical model will soften under mechanical abuse. Based on this, the first order derivative of the load force to displacement (df/dx) of the equivalent mechanical model is carried out. The results show that the displacement of df/dx extreme value can better reflect the mechanical failure and soft short circuit of the battery, the average prediction error is 10.91% and 5.46% which always in advance of the actual failure. So, the failure criteria of lithium-ion batteries related to state of charge are proposed. In the future, these criteria can be used as the reference basis for judging the failure of lithium-ion batteries based on mechanical penetration and the simple form of the prediction criteria can be easily programmed into the controller.