Electro-thermal modeling of high-performance lithium-ion energy storage systems including reversible entropy heat

Abstract

Two of the major heat sources in a high-performance automotive lithium-ion battery cell are parameterized in this study: Joule heat and entropy heat. Established electrochemical models are investigated and experiments are designed to acquire the relevant parameters such as open circuit voltage, entropy coefficient and internal impedance from ohmic losses and mass transport. It is shown that the irreversible joule heat and the reversible entropy heat has a similar magnitude at many operating points for the device tested. The strong influence of irreversible entropy heat has the potential to absorb all the joule heat in currents up to 135 A (C-rate of 13.5) charging and 66 A (6.6 C) discharge in a power optimized automotive lithiumion cell. It is also shown that, by including the entropy heat in a simple thermal model, the temperature error can be reduced down to 28 % and 44 % for under charging and discharging with high currents, respectively.