Polyurethane-based flexible and conductive phase change composites for energy conversion and storage

The widespread utilization of phase change materials (PCMs) in thermal energy storage technologies is often limited by the shape instability, rigidity, low conductivity and lack of multi-driven capabilities. Therefore, the functionalization of PCMs in order to overcome the aforementioned issues has remained an elusive goal. Herein, we infiltrate a polyethylene glycol (PEG) based solid-solid PCM into the pores of carbon nanotube sponge (CNTS) to fabricate a dual form-stable, flexible and highly conductive phase change composites (PCCs). The developed PCCs undergo nanopore-confined solid-solid phase transition triggered by a low voltage or sunlight with high electro/photo to thermal energy storage efficiency (>94%). The reported energy conversion efficiencies for both electro and photo to thermal energy storage is highest among all functionalized PCCs and attributed to the excellent energy conversion/transfer performance of aligned carbon nanotubes (CNTs) network in the composite structure. In addition to extra shape stability, the solid-solid PCC present high axial thermal conductivity (2.4 W m−1k−1) as well as high-energy storage density 132 J g−1 which is close to solid-liquid PCCs. Therefore, this study provides routes towards the development of real-life applicable PCCs for thermal energy applications.