Flame-retardant wood-based composite phase change materials based on PDMS/expanded graphite coating for efficient solar-to-thermal energy storage

Wood-based composite phase change materials (PCMs) have considerable development potential in shape-stable thermal energy storage. However, Wood-based composite PCMs possess inflammability due to wood-based supporting materials and organic PCM, which limits its practical application. In this work, a novel strategy of wood-based composite PCMs with flame retardant coating is adopted, in which the introduction of expanded graphite (EG)-based coating can not only enhance the flame retardant property, and EG can be used as photothermal material to improve the photothermal conversion efficiency. The flame-retardant wood-based composite PCMs show excellent flame retardant properties, which peak of heat release rate (pHRR) is reduced by 40.1–52.3% compared with PEG-1000@delignified wood (DW). It is worth noting that when the amount of EG is >0.5 g, the flame-retardant wood-based composite PCMs can be completely protected in the ignition combustion test, and the combustion flame is extinguished by itself. The loading mass fraction of the PEG-1000 of the flame-retardant wood-based composite PCMs is 53.1–73.4%, which shows that it has good energy storage performance. At the same time, the flame-retardant wood-based composite PCMs still have good cycle reliability after 100 heating-cooling cycles. Due to the excellent light absorption properties of EG, the flame-retardant wood-based composite PCMs exhibit excellent photothermal conversion efficiency (68.1–80.0%), which has considerable application potential in solar energy utilization systems and thermal management.