Enhanced cooling performance of lithium polymer batteries using micro heat pipes integrated with carbon nanotubes coatings

• CNT-MHP achieves 71 % higher thermal conductivity than uncoated MHP for battery cooling. • CNT-MHP maintains LiPo battery temperatures below 35 °C at discharge rates up to 9 A. • Oxygenated CNT coatings enhance capillary action and phase-change heat transfer. • Molecular dynamics reveals CNT oxidation enhances water transport and evaporation. Effective thermal management is essential for optimizing the performance, lifespan, and safety of lithium polymer (LiPo) batteries, particularly under high discharge rates. This study experimentally investigates the thermal performance of water-charged carbon nanotube-coated micro heat pipes (CNT-MHP) as an advanced cooling solution. Comparative benchmarks include air forced convection (FC), uncharged micro heat pipes (U-MHP), and conventional water-charged uncoated micro heat pipes (C-MHP). The CNT-MHP utilizes highly efficient phase-change heat transfer, enabled by ultrafast water transport, which simultaneously enhances evaporation, condensation, and circulation processes in a heat pipe. The CNT-MHP significantly outperforms other methods, demonstrating up to a 71 % improvement in effective thermal conductivity and a 24 % higher heat transfer coefficient compared to the C-MHP. When applied to LiPo battery cooling, the CNT-MHP maintains a surface temperature of 31.7 °C, well below the 35 °C healthy threshold, even at a high discharge rate of 9 A. This marks a temperature reduction of over 7.3 °C compared to forced convection. Molecular dynamics simulations reveal the role of CNT nanostructures in enabling rapid water permeation and efficient heat transport. These results demonstrate the potential of CNT-MHP as a transformative cooling solution, ensuring safer and more reliable operation of energy storage systems under demanding conditions.