Comprehensive Study on Thermal Characteristics of Lithium-Ion Battery With Entropic Heat

Abstract

Most battery thermal models have been validated at low C-rates, often overlooking the influence of entropic heat (EH) owing to its relatively small magnitude. However, at high C-rates, the exclusion of EH can lead to significant temperature deviations. In this context, this study investigated the influence of EH on battery temperature under various operating conditions. Experiments were conducted to determine the entropic coefficient (EC), and an electrochemical–thermal-coupled battery model was developed and validated using experimental data under various discharge conditions. The results showed that the effect of EH on battery temperature increased as the C-rate increased. With the consideration of EH, the battery shows up to 7 K temperature difference at the 3 C discharge rate with ambient temperature at 25°C. The effect of EH on battery temperature became prominent at low ambient temperatures. A temperature difference of 12.4 K was observed at the 3 C discharge rate with ambient temperature at −10°C. Additionally, using the developed battery thermal model, the temperature variations of 6, 8, and 10 C discharge were investigated. This model can estimate the battery thermal behavior over 60°C when the destruction of solid electrolyte interphase (SEI) layers begins. For practical implementation, the battery thermal model developed at the cell level was extended to the module level. With the reflection of EH, temperature differences of up to 1.7, 3.7, and 6.7 K are observed at 1, 2, and 3 C discharge rates, respectively.