Electrochemical-thermal coupling model of lithium-ion battery at ultra-low temperatures

Most models fail to describe the behavior of LiCoO₂/graphite lithium-ion batteries at ultra-low temperatures, which limits the application of lithium-ion batteries in extreme climates. Model parameters at low temperatures must be accurately obtained to resolve this issue. First, the open-circuit potential curve and entropy coefficient curve of the electrode material were measured by assembling the half-cell. Secondly, to simulate the “fishhook curve” of the discharge voltage at low temperatures, corrections are made for liquid phase diffusion and reaction polarization parts, and the current excitation is designed separately to identify the model parameters at ultra-low temperatures. The accuracy of the model and parameters is verified by evaluating the model for galvanostatic discharge tests in the temperature range of −40 °C to 25 °C. The results show that the model can accurately predict the voltage and temperature curves and simulate the “fishhook curve” at ultra-low temperatures.