Thermal performance optimization of lithium-ion battery packs using liquid immersion cooling with a stepped staggered baffle structure

To ensure the safe operation of large-capacity lithium-ion battery energy storage systems (BESSs), immersion cooling has emerged as a promising thermal management solution owing to its excellent heat-transfer properties. However, flow channel optimization for large-scale frameworks remains underexplored. To address this gap, this study establishes a novel battery thermal management system featuring a stepped staggered baffle structure, which simultaneously enhances cooling performance along the flow and cell height directions. Numerical simulations were conducted to explore the influence of key structural and operational parameters, including coolant flow rate (0.05–0.25 kg/s), baffle height step (27–34.5 mm), baffle width (13.7–163.7 mm), inter-cell spacing (5–10 mm), and cell-to-sidewall clearances (4–9 mm). Results revealed that compared to designs with no baffles or alternative baffle configurations, the stepped staggered baffle structure reduces both the maximum temperature and maximum temperature difference within the battery module. Increasing the baffle height or coolant velocity continuously reduces critical temperature metrics. Conversely, when the baffle width, inter-cell spacing, or distance between cells and sidewalls is increased, the maximum temperature and temperature difference first decrease and then increase. To achieve the optimal balance between thermal performance and power consumption, an optimal configuration was identified (baffle height step: 34.5 mm, baffle width: 73.7 mm, inter-cell spacing: 8 mm, and cell-to-sidewall clearance: 7 mm), achieving reductions of 15.9% and 17.7% in the maximum temperature and maximum temperature difference, respectively. Overall, this research provides a viable technological pathway and design reference for the effective thermal management of BESSs.