MXene reconciles concurrent enhancement of thermal conductivity and mechanical robustness of SiC-based thermal energy storage composites

Abstract

Latent heat thermal energy storage techniques based on phase change materials (PCMs) play a vital role in efficient and stable utilization of intermittent solar and thermal energy sources. However, low thermal conductivity and poor mechanical strength are daunting bottlenecks of traditional PCMs, inhibiting their wide applications. Here, we successfully enhance both thermal conductivity and mechanical robustness of porous SiC-based composite phase change materials (CPCMs) via doping MXene into SiC skeletons, which are superior to state-of-the-art ceramic CPCMs. The thermal conductivity of MXene-doped CPCMs achieves 15.21 ​W/(m·K) at a porosity of 72.9%, which is 25% higher than that of undoped counterparts. The underlying mechanism lies in that the oxide layer on the surface of MXene melts at a high temperature, filling the gap between SiC grains and optimizing the thermal transport path. Compared with virgin SiC skeletons, the flexural strength and compressive strength of MXene-doped skeletons are enhanced by 20% and 29%, respectively. This is because MXene removed from the oxide layer disperses in the ceramic matrix and improves the mechanical strength of the composite through pull-out, crack deflection and the change of fracture mode. Superior cycle stability and thermal shock resistance are also demonstrated. High thermal conductivity, robust mechanical strength, exceptional stability, and high solar absorptance enable prepared composites to realize high-performance dual-functional thermal and solar energy storage.