Shape-stabilized and flexible phase change materials with enhanced photothermal conversion for efficient thermal energy storage

Thermal energy storage (TES) systems with phase change materials (PCMs) can efficiently address the intermittency and uneven distribution of solar energy. However, easy leakage, inherent rigidity, and poor photothermal conversion capacity greatly limits their practical utilization. Herein, a novel shape-stabilized composite PCMs with heat-induced flexibility and excellent photothermal conversion efficiency was prepared by impregnating a mixture of polyethylene oxide (PEO) and polyethylene glycol (PEG) into cuttlefish ink (CI) melanin decorated melamine foam (MF). To promote its long-term stability, a physical barrier of polydimethylsiloxane (PDMS) coating was applied to its surface. Finally, a series of innovative PEO/PEG@CI/MF-PDMS (PPCMP) PCMs with different concentrations of CI were successfully fabricated. The PPCMP composite PCMs possess high quality retention (94.39–97.45 %) when heated at 80 °C and flexibility when heated or light irradiated, indicating their excellent anti-leakage performance and heat-induced flexibility. And the incorporation of CI-derived melanin has endowed PPCMP composite PCMs with remarkable photothermal conversion efficiencies (83.26–93.67 %) due to its wide light absorption. More importantly, the optimized PPCMP composite exhibits a satisfactory melting enthalpy (>160 J/g) and high enthalpy efficiency (>80 %). Moreover, PDMS coating imparts the composites with outstanding hydrophobicity (WCA>100°), and PPCMP demonstrates thermal stability below 100 °C and reliability after multiple cycles. Based on the above merits, this work offers a prospective strategy for constructing shape-stabilized and flexible PCMs with excellent photothermal conversion and energy storage performance for practical applications in personal thermal management and flexible electronics.