Pressure-regulated pool boiling for lithium-ion batteries based on a thermo-lifetime-economic coupling framework

Abstract

Pool boiling cooling offers strong potential for lithium-ion battery thermal management due to its high-efficiency phase-change heat transfer. However, most existing studies are limited to atmospheric pressure, and the coupled effects of pressure on thermal behaviour, battery lifetime, and economic performance remain unclear. In this study, a thermo-lifetime-economic coupling model is developed and experimentally validated through pressure-controlled pool boiling cooling of a battery module over a pressure range of 20–100 kPa. The results show that pool boiling significantly outperforms natural air-cooling, reducing the maximum temperature from 88.8 °C to 45.6 °C (48.6%) and the temperature difference from 9.3 °C to 3.1 °C (66.7%) at 2.5C. Further pressure reduction enhances thermal performance by lowering the saturation temperature and promoting earlier nucleate boiling. When the pressure decreases from 100 kPa to 20 kPa, the maximum temperature and temperature difference are further reduced by 26.3% and 38.7%, respectively, leading to a lifetime improvement of up to 65.1%. However, this improvement is accompanied by a substantial increase in auxiliary power consumption, which rises by more than 14.6 times, resulting in a strong thermo-economic trade-off with diminishing returns at low pressures. Furthermore, system scale critically affects economic feasibility. Pressure reduction increases cost at small scales but becomes favourable beyond a critical scale due to the growing contribution of lifetime-related cost. These results show that pressure regulation can improve pool boiling battery cooling, but the operating pressure should balance thermal performance, lifetime, and energy consumption.