Influence of temperature, state of charge and state of health on the thermal parameters of lithium-ion cells: Exploring thermal behavior and enabling fast-charging

Abstract

The precise input of thermal parameters is essential for thermal simulation. Although constant thermal parameters are commonly used for parametrizing thermal modeling frameworks, extensive measurements indicate a significant dependence of thermal parameters on temperature, SOC and SOH. Therefore, this work summarizes experimental data and integrates determined operating point dependencies into a validated thermal-electrical-electrochemical modeling framework. Exploring the effect of variable thermal parameters, detailed effects on fast-charging and corresponding charging times are assessed.

It is found that the strong reduction in through-plane thermal conductivity due to aging can notably increase thermal inhomogeneity. Thus, heat dissipation is reduced and the thermal management has to be revised to prevent an increase in charging time of up to 3%. However, the operating point-dependent through-plane thermal conductivity has no significant effect on fast-charging for the analyzed pristine cylindrical lithium-ion cell. Furthermore, a temperature-dependent specific heat capacity definition considerably affects the thermal behavior of lithium-ion cells at extreme temperatures. While enabling a faster heating at low temperatures, a temperature-related current derating at high temperatures is delayed. Thus, a variable thermal parameter definition can lead to an increase in fast-charging capability of up to 3% due to the more precise modeling of the physical behavior of the cell.