Largely enhanced thermal conductivity of poly (ethylene glycol)/boron nitride composite phase change materials for solar-thermal-electric energy conversion and storage with very low content of graphene nanoplatelets

- Very low content of GNP is introduced into PEG/BN composite PCMs.
- Thermal conductivity and photoabsorption ability of composite PCMs are enhanced.
- GNP contributes to the perfect conductive network and sunlight harvesting ability.
- Solar-to-thermal & solar-to-electric energy conversion and storage are realized.

Phase change materials (PCMs) with high thermal conductivity and efficient solar energy conversion have recently attracted much attention. However, a facile strategy to enhance thermal conductivity and realize energy conversion and storage is still eagerly desired. In this work, a very low content of graphene nanoplatelets (GNP) is introduced into poly (ethylene glycol) (PEG)/boron nitride (BN) composite PCMs, resulting in great improvement in thermal conductivity and photoabsorption ability via a facile solution blending process. The presence of GNP contributes to enhancing thermal conductivity and realizing efficient solar energy conversion (including solar-to-thermal and solar-to-electric energy conversion) for the PEG/BN/GNP composite PCMs owing to the formation of improved BN/GNP thermally conductive network and the improvement of sunlight harvesting ability, respectively. Thermophysical properties demonstrate that compared with PEG/BN composite PCMs at the same BN content, PEG/BN/GNP composite PCMs containing a low GNP content maintain comparable energy storage density. The study sheds light on the realization of solar energy utilization and storage of the organic PCMs requiring high thermal conductivity.

A kind of multifunctional composite PCMs with synergistic enhancement of thermal conductivity by introducing BN and very low content of GNP for light-thermal-electric energy conversion and utilization have been developed.130