The rise of the energy storage technology revolution has brought with it a series of thermal runaway issues. To address the problem of thermal runaway in energy storage batteries, a method combining CFD numerical simulation and 3D modeling was employed, with the simulation objectives focusing on the maximum and minimum battery temperatures. An appropriate insulating liquid was selected for simulation calculations based on experimental comparisons and economic considerations. A simulation model of an immersion cooling system combined with cold plates for a lithium iron phosphate (LFP) battery pack was established to compare the heat dissipation performance of the battery pack under different coolant flow rates in the cold plates. The research results indicate: Experimental comparisons of vegetable oil, synthetic oil, and fluorinated liquid revealed that the immersion cooling method can confine the cell temperature below 300 ℃ during a thermal runaway event. Furthermore, this method suppresses thermal runaway rapidly and shortens the duration of the thermal runaway process. Crucially, none of the tested oils triggered thermal runaway. Synthetic oil was ultimately selected as the insulating fluid due to its superior cost-effectiveness. As the volumetric flow rate increased, the temperature of the synthetic oil decreased correspondingly, resulting in significantly enhanced heat dissipation for the entire battery pack.