Investigations of phase change materials in battery thermal management systems for electric vehicles: a review

Taking advantage of electric vehicles' low pollution, the world is changing its face toward electric vehicle (EV) production. As EVs rely heavily on specialized batteries, it's important to manage them safely and properly to prevent thermal runaway. High ambient temperatures and varied charging/discharging rates increase battery temperature. To address these challenges, Battery Thermal Management System (BTMS) come into play. This work focuses on passive cooling in BTMS, which is one of two categories of BTMS, with the other being active cooling using liquid-air systems. Passive BTMS has gained prominence in research due to its cost-effectiveness, reliability, and energy efficiency, as it avoids the need for additional components like pumps/fans. This article specifically discusses recent experimental studies regarding phase change material (PCM)-based thermal management techniques for battery packs. It explores methods for enhancing thermal conductivity in PCMs and identifies methodologies for BTMS experiments using PCMs. Also recommends the importance of optimization techniques like machine learning, temperature sensors, and state-of-charge management, to ensure accuracy and uniform temperature distribution across the pack. While paraffin wax has been a popular choice in experimental studies for its capacity to absorb and release heat during phase transitions, as a matter of its low thermal conductivity (0.2 to 0.3 Wk-1m-1) limits reaction in rapid charging/discharging of batteries. So integration with highly thermally conductive additives is recommended. Additives such as heat pipes offer superior thermal conductivity compared to expanded graphite (5 to 200 Wk-1m-1). As a result, the integration of heat pipes further reduces the temperature of battery by 28.9% in addition to the reduction of 33.6% by pure PCMs in time of high charge/discharge rates (5 C to 8 C). So high-conductivity additives correlate directly with improved thermal performance and are essential for maintaining optimal battery temperatures and overall reliability in EV battery packs.