Abstract: ObjectivesThis study optimizes the structure and thermal performance of an immersed liquid cooling system to enhance thermal management and temperature uniformity in large-capacity marine battery packs under high-rate discharge. MethodsA thermal model of a square LiFePO₄ battery was developed and validated experimentally. CFD simulations analyzed the effects of inlet/outlet layout, number of injection holes, battery spacing, flow velocity, and coolant type. Multi-objective optimization using the Kriging model and NSGA-Ⅱ algorithm was applied to minimize maximum temperature and temperature difference. ResultsA three-injection-hole configuration reduced the maximum temperature by 9.5% and the maximum temperature difference by 24.9%. A 10 mm lateral spacing decreased the maximum temperature difference by 52.0%. At 1.5 m/s flow velocity, the maximum temperature and temperature difference were reduced by 16.9% and 45.1%, respectively. Using ionic water instead of synthetic oil lowered the maximum temperature and temperature difference by 18.3% and 73.4%. The optimized system achieved a maximum temperature of 23.62°C and a maximum temperature difference of 3.33°C, with errors below 2.5%. ConclusionThe optimized immersed liquid cooling system significantly improves thermal safety and temperature uniformity, providing valuable insights for designing cooling systems for large-capacity battery packs.