A Novel Heat Pipe for Internal Cooling for Cylindrical Cells in EV Battery Packs

Despite significant advances in battery thermal management for electric vehicles, efficient and non-intrusive solutions capable of directly extracting heat at the cell level remain challenging. This work presents a novel copper heat pipe for the thermal management of cylindrical LiFePO4 battery. The device is geometrically adapted to the cell profile, enabling non-invasive integration between adjacent cells without modifications to the pack architecture. Its convex contact surfaces naturally form capillary grooves, eliminating conventional wick structures while ensuring effective fluid transport. Experimental evaluation was conducted under controlled electrical heating and realistic battery operation conditions. The device demonstrated a thermal resistance reduction of 88.82% compared with the empty configuration, confirming the effectiveness of the phase-change mechanism and grooved copper geometry. Stable two-phase operation was observed across the entire tested range (5–25 W), with early activation of the working fluid at low heat loads (5 W), ensuring efficient thermal transport under battery-relevant conditions. The proposed heat pipe achieved temperature reductions of up to 9.67 °C under 30 A (2C) discharge conditions compared with a system without thermal management. Overall, the results demonstrate a passive, scalable, low-complexity solution fully compatible with existing cylindrical lithium-ion battery pack configurations while significantly improving thermal performance.