Flexible phase change materials for thermal energy storage

Phase change materials (PCMs) have been extensively explored for latent heat thermal energy storage in advanced energy-efficient systems. Flexible PCMs are an emerging class of materials that can withstand certain deformation and are capable of making compact contact with objects, thus offering substantial potential in a wide range of smart applications. To realize the flexibility, the energy storage capacity of flexible PCMs is partially reduced by the presence of thermally inactive flexible supports. Considering this tradeoff, several versatile methodologies have been proposed to develop flexible PCMs with optimal energy storage capacity and device-level flexibility. In this article, we systematically reviewed these strategies including (1) confinement of rigid PCM into flexible porous scaffolds, (2) encapsulation of PCM into elastic shells, and (3) development of intrinsically flexible PCM based on molecularly engineered structures. Besides, the applications of flexible PCMs in diverse fields including thermal management of electronic devices, thermal therapy of the human body, and flexible sensors have been presented. Finally, the major problems associated with the development of flexible PCMs and their prospective solutions are provided in detail.