Preparation of three-dimensional interconnected graphene/ionic liquid composites to enhanced thermal conductivities for battery thermal management

Abstract

The development of phase change materials with a high latent heat of fusion and thermal conductivity is a key issue that needs to be addressed in power batteries thermal management system. In this study, an imidazolium ionic liquid ([C16MIM]Br) suitable for latent heat storage was synthesized by quaternization reaction. The composite phase change material of ionic liquid/graphene/carbon nanotube aerogel was prepared by hydrothermal self-assembly and vacuum impregnation method utilizing the unique π-π interaction between the delocalized electron of the heterocyclic cation of the ionic liquid and the sp2 bonded carbon materials. The prepared ionic liquid-based phase change materials had high latent heat of phase change, excellent thermal stability, and enhanced thermal conductivity. The thermal conductivity of the composite material reached 0.751 W/(m·K) at a carbon nanotubes addition of 15 wt%, which was 232% higher than that of the pure ionic liquid (0.226 W/(m·K)). The enhancement was attributed to the three-dimensional network in the graphene/multi-walled carbon nanotubes aerogel which was beneficial to improve the dispersion of multi-walled carbon nanotubes in the matrix and promote the uniform penetration of the ionic liquid phase change material. As a result, the designed structure provided effective ways for phonon transmitting and improved the thermal conductivity of the composites.