Water-Immersion Cooling for Lithium-Ion Battery Thermal Management: A Systematic Experimental and Numerical Study

In recent years, immersion cooling has gained wide interest for thermal management of lithium-ion batteries. Usually, dielectric oils or fluorinated liquid are used as immersion coolants to avert short circuits, but they have low thermal conductivity and high cost. Although water offers superior heat-transfer performance, its poor dielectric property means it cannot be used directly as an immersion coolant. Near full-depth partial immersion (NFDPI) was proposed as a viable alternative, in which water does not contact the tabs of batteries. In this study, an NFDPI experimental system is set up, and the effects of coolant flow rate, discharge rate, and inlet–outlet configuration on thermal management performance are investigated. Since direct observation of the immersion tank’s internal flow is challenging, numerical simulations are conducted to resolve the flow field under various operating conditions. The experimental and simulated results reveal that NFDPI cooling effectively limits the module’s maximum temperature, and the module’s maximum temperature spread is mainly attributed to the cell’s vertical temperature gradient. These findings offer guidance for the practical deployment of water-based NFDPI lithium-ion battery energy storage systems.