Optimization of Thermal Performance in Immersion Liquid-Cooled Prismatic Lithium-Ion Battery Modules for Energy Storage: An Experimental and Numerical Study

Heat generated during charging and discharging cycles can degrade lithium-ion battery performance and lead to thermal runaway. This study presents an immersion liquid cooling system for prismatic lithium-ion energy storage battery modules, and evaluates its thermal performance through experiments and simulations. Experimental results indicated that natural air cooling allowed both the average module temperature and maximum temperature difference to exceed safe limits. Immersion cooling reduced the maximum temperature difference by 33.1% and the average temperature by 17.3% compared to natural cooling. Optimal thermal performance occurred at a coolant temperature of 25 °C and a flow rate of 1.75 L/min; further increases in flow rate or temperature reduced efficiency. To explore the influence of system design, numerical simulations using ANSYS Fluent integrated fluid-thermal coupling model and Battery heat generation model. This study investigated the effects of inter-battery spacing, tank dimensions, and novel structural designs. An 8 mm spacing provided the best compromise between flow behavior and heat transfer characteristics. Structural optimization of the immersion tank was found to reduce the maximum temperature difference across the module by up to 14.36%. An ejector-style inlet-outlet configuration combined with a layered design reduced the average temperature by 2.17 °C and decreased the maximum temperature difference by 36.34% compared with the initial case. These findings demonstrate that the optimized structural design can remarkably improve cooling performance, thereby offering a practical and viable solution for the immersion liquid cooling system of lithium-ion batteries.