Thermal-electrical characteristics of lithium-ion battery module in series connection with a hybrid cooling

Abstract

The thermal management is of vital importance for the secure and highly efficient operation of lithium-ion battery pack. In this work, a new hybrid thermal management system combined with PCM and liquid cooling by a thermal conductive structure is proposed, and the electrochemical-thermal coupling models are developed for the lithium-ion battery module connected in series, by which the hybrid cooling system is preliminarily optimized by studying the effects of separation between cells and inlet water velocity on the electrochemical and thermal performances. The maximum temperature and maximum temperature difference decrease as the separation increases, but the drop rate gets small when the separation exceeds 4 mm. Moreover, the maximum temperature falls while the maximum temperature difference rises with increasing the water velocity. A theoretical calculation is adopted to analyze and quantified the uneven discharge, finding that the diffusion polarization in electrolyte is the key issue for the discharge unbalance among the cells in battery module, which can be improved by the proposed hybrid cooling. Finally, the optimized inlet water temperature of 30 ℃ is recommended, at which the discharge and temperature uniformities perform best, and the maximum temperature is kept below 40 ℃.