Enhancing fast charging performance of lithium-ion batteries: The role of operating temperature and charging rate

Increasing the operational temperature and charging rate can expedite the fast charging process of lithium-ion batteries, but these enhancements also accelerate the formation of solid-electrolyte interfaces (SEI) and heighten the risk of lithium plating, thereby accelerating cell aging. To explore the influence mechanisms of operating temperature and charging rate on fast charging performance, this paper develops and validates an electrochemical-thermal coupling model that incorporates polarization, heat generation, and side reactions. This model is based on extensive cell charging rate testing and is employed to numerically investigate the impacts of operating temperature and charging rate on fast charging performance and heat generation under both isothermal and non-isothermal conditions. Metrics such as charging capability and anti-aging capacity are utilized in this analysis. Our findings indicate that an increase in operating temperature significantly enhances the cell's charging capacity, with the primary factor of capacity loss shifting from lithium plating to SEI growth. We identify an optimal charging temperature that minimizes capacity loss due to SEI formation. As the charging rate increases, while the cell's charging capacity improves, the risk of lithium plating rises and the SEI growth rate accelerates, although the reduced charging duration mitigates the overall capacity loss. Under consistent operating conditions, the SEI growth rate varies across charging, resting, and discharging phases. Furthermore, operating temperature and charging rate differentially impact the heat sources of various internal reactions within the cell, leading to an increase in cell temperature and thus affecting fast charging performance. Notably, a higher charging rate not only shortens the charging time but also leverages the generated heat to enhance charging capability while reducing capacity loss associated with side reactions. The results of this study will contribute to the development of more efficient and safer fast charging strategies.