Heat transfer enhanced inorganic phase change material compositing carbon nanotubes for battery thermal management and thermal runaway propagation mitigation

Developing technologies that can be applied simultaneously in battery thermal management (BTM) and thermal runaway (TR) mitigation is significant to improving the safety of lithium-ion battery systems. Inorganic phase change material (PCM) with nonflammability has the potential to achieve this dual function. This study proposed an encapsulated inorganic phase change material (EPCM) with a heat transfer enhancement for battery systems, where Na₂HPO₄∙12H₂O was used as the core PCM encapsulated by silica and the additive of carbon nanotube (CNT) was applied to enhance the thermal conductivity. The microstructure and thermal properties of the EPCM/CNT were analyzed by a series of characterization tests. Two different incorporating methods of CNT were compared and the proper CNT adding amount was also studied. After preparation, the battery thermal management performance and TR propagation mitigation effects of EPCM/CNT were further investigated on the battery modules. The experimental results of thermal management tests showed that EPCM/CNT not only slowed down the temperature rising of the module but also improved the temperature uniformity during normal operation. The peak battery temperature decreased from 76 °C to 61.2 °C at 2 C discharge rate and the temperature difference was controlled below 3 °C. Moreover, the results of TR propagation tests demonstrated that nonflammable EPCM/CNT with good heat absorption could work as a TR barrier, which exhibited effective mitigation on TR and TR propagation. The trigger time of three cells was successfully delayed by 129, 474 and 551 s, respectively and the propagation intervals were greatly extended as well.