An investigation of heat transfer and capacity fade in a prismatic Li-ion battery based on an electrochemical-thermal coupling model

A large format lithium-ion (Li-ion) battery significantly suffers from a nonuniform thermal distribution, which adversely affects the electrochemical reaction inside the battery and accelerates its degradation. In this work, a one-dimensional (1D) electrochemical-three-dimensional (3D) thermal coupling model is developed to investigate the heat transfer of a prismatic Li-ion battery when cooling different external surfaces. Simulation parameters are considered, including a forced convection cooling coefficient, h, the surface area of heat dispersion and the battery size. Despite the side surfaces of the prismatic Li-ion battery being small, the orthotropic thermal conductivity of the prismatic battery improves the planar heat transfer and effectiveness of forced convection cooling on the small side surfaces. It is found that the temperature distribution in the prismatic battery with forced convection cooling on the small side surfaces is more uniform than cooling the large front surfaces. At h = 100 W/m2 K, as the battery size increases, the maximum temperature difference of the prismatic battery with small side surface cooling stays at a constant value of 3.18 °C. In addition, the effect of operating temperature on the capacity fade of Li-ion batteries during cycling is investigated. It is found that a high operating temperature accelerates the parasitic lithium/solvent reduction reaction, and the above reduction reaction results in the loss of Li ions and increases the rate of capacity fade during the cycling process.