Model-Based Electrochemical and Thermal Analysis of Lithium-Ion Battery Under Fast Charging With Excessive Forced Convection Cooling condition

Lithium-ion batteries (LIBs) overheating caused by fast charging extremely enhances the risk of battery thermal runaway and the resulting fire and explosion accidents, severely threating electric vehicle safety. To relief the temperature rise of batteries during fast charging, forced convection cooling is expected but improper cooling strategy may lead to lithium plating and thermal inhomogeneity. For investigating the LIB electrochemical and thermal characteristics under forced convection condition, a multi-dimensional electrochemical–thermal coupled model of 2.6Ah 18650 LIB is developed in this work, with which effects of charging rate and convection heat transfer coefficient are clarified. From the results, the critical charging rate of lithium plating is 4 C, and with further increased charging rate, nonlinear growth of abnormal electrochemical characteristics related to lithium plating indicating shorten lifetime and enhanced possibility of internal short circuit. At high charging rate, irreversible heat showing difference in different LIB components dominates the total heat generation, causing large temperature rise and uneven temperature distribution inside the LIB, extremely enhancing the risk of over-aging and thermal runaway. Adopting high convection heat transfer coefficient is proved to effectively alleviate the temperature rise at large charging rate, but the augmented levels of heat generation with large difference of thermal conductivity inside and outside the LIB induce a large temperature gradient, causing inhomogeneity in electrochemical characteristics and an enhancement of lithium plating. These findings will provide effective guidance for developing appropriate cooling strategy to achieve reliable fire protection while minimizing the adverse effects of cooling.