Highly conductive phase change composites enabled by vertically-aligned reticulated graphite nanoplatelets for high-temperature solar photo/electro-thermal energy conversion, harvesting and storage

Abstract

Thermal energy harvesting and storage with phase change materials (PCMs) plays a broad and critical role in solar-thermal utilization and energy management. However, the intrinsic low thermal conductivity of PCMs and slow thermal transport are great challenges for accelerating PCM-based thermal energy harvesting & storage. Herein, we report a synergetic strategy for synthesizing scalable highly conductive phase change composites (PCCs) and tailoring thermal transports by aligning self-assembled large-size reticulated graphite nanoplatelets (RGNPs) inside PCCs. The vertically-aligned and layered large-size RGNPs enable the directional thermal and electrical conductivities of PCCs up to 33.5 W/mK and 323 S/cm respectively at RGNPs loading below 25 wt%, superior to the state-of-the-art PCCs. Inspired by the synergetic effects of vertically-aligned RGNPs inside PCCs with directional thermal/electrical transports, the versatile PCC-based energy devices set up new records for sunlight-driven direct photo-thermal energy harvesting & storage at high-temperature heats (>186 °C) without optical concentration, and ultralow voltage-driven (< 0.34 V) fast electro-thermal energy conversion & storage with high efficiency (~ 92.7%). Our work provides a cost-effective route to fabricate scalable highly conductive PCCs and synergetic strategy to realize efficient PCM-based energy management for solar-thermal utilization and other heat-related processes. A novel highly conductive scalable PCC was synthesized by aligning self-assembled large-size reticulated graphite nanoplatelets (RGNPs) for efficient photo/electro-thermal conversion & storage. The vertically-aligned and continuous large-size RGNPs enable the resultant PCCs to exhibit ultrahigh thermal and electrical conductivities up to 33.5 W m -1 K -1 and 323 S cm -1 , respectively. The obtained PCCs combined with the solar-thermal conversion layer realize direct solar photo-thermal conversion & storage above 186 °C without optical concentration. Moreover, the PCC also exhibits highly efficient electro-thermal energy conversion & storage (~92.7%) under the ultralow driving voltage of 0.34 V. • A strategy for synthesizing highly conductive phase change composites (PCCs) by vertically-aligned RGNPs. • The PCC exhibits ultrahigh thermal conductivity up to 33.5 W m -1 K -1 and superior electrical conductivity of 323 S cm -1 . • Sunlight-driven direct photo-thermal energy harvesting & storage by the PCC above 186 °C without optical concentration. • Efficient electro-thermal energy conversion & storage by the PCC under ultralow driving voltage (<0.34 V).