Form-Stable phase change composites with high thermal conductivity and enthalpy enabled by Graphene/Carbon nanotubes aerogel skeleton for thermal energy storage

Abstract

Thermal energy storage offers enormous potential in energy utilization and phase change materials (PCMs) plays a crucial role in energy management. However, the intrinsically low thermal conductivity, easy liquid leakage and low latent heat of PCMs are great challenges for enabling their use. Herein, a novel method was developed to solve the drawbacks of PCMs by encapsulation of reduced graphene oxide/carbon nanotubes hybrid aerogels (rGCA). The rGCA with interconnected network structures was prepared through chemical reduction and self-assembly under atmospheric pressure drying using carbon nanotubes as the supporting skeleton. The rGCA as 3D scaffold could accommodate paraffin wax (PW) to obtain PW/rGCA phase change composites, which showed excellent shape stability even heating above melting point of PW, and no obvious liquid leakage occurred. PW/rGCA exhibited excellent phase change ability with high phase change enthalpy of 236.7 J/g, which was close to that of pure PW. Moreover, the phase change enthalpy of PW/rGCA still maintained 96.5 % of initial PW even after 100 cycles, revealing the good long-term thermal and chemical stability. The pre-constructed continuous 3D thermally conductive network enabled the thermal conductivity of PW/rGCA up to 1.897 W/mK, much higher than that of pure PW and PW/rGA. The higher thermal diffusion of PW/rGCA resulted in the faster temperature change rate, exhibiting highly reversible thermal behavior of absorbing and releasing heat energy. Furthermore, crosslinked natural rubber (NR) chains were introduced into rGCA to enhance the mechanical property and elasticity, and PW/NR@rGCA composites showed excellent shape stability, good phase change ability and high thermal conductivity, revealing promising applications in energy storage.