Semi-empirical model for cycling aging of lithium-ion battery with C-rate and temperature

Extreme fast charging is a key technology for alleviating range anxiety in electric vehicles, but the side reactions and heat generation induced by high C-rates can impair battery cycle life. Existing models often neglect the coupled effects among cycle life, C-rate, and temperature. Therefore, we develop a Cycle & C-rate, Elevated temperature (CARE) model to quantify these relationships. The model establishes the above relationship using the characteristic time. It is calculated from key parameters that dominate battery C-rate performance, which are identified by sensitivity analysis. Based on the CARE model, the preheating temperature at a given C-rate can be estimated according to the target cycle number, thereby guiding the preheating process before charging to regulate capacity degradation. To verify the accuracy of the CARE model, we calculate that preheating temperatures of 43 °C and 50 °C would enable commercial NMC/graphite pouch cells to achieve more than 500 and 600 cycles under extreme fast charging, respectively. Then the experiments are conducted accordingly. The results show that batteries can achieve the expected cycle number when the preheating temperature is 43 °C. However, the CARE model does not account for the thickening and compositional changes at the solid electrolyte interphase caused by overheating. The scope of application for the CARE model can be further expanded. Overall, the CARE model provides a practical semi-empirical framework for lifetime-oriented preheating-temperature screening under different C-rate and temperature conditions.