▎ 摘　　要

Molten salt is considered as one of the most promising candidate materials for solar energy storage due to its consistent performance and high energy storage density. The limited thermal conductivity of molten salt, on the other hand, has become a bottleneck for efficient energy storage and heat transfer. Here, we propose a composite phase change material (PCM) to realize ultrafast thermal energy storage based on sodium nitrate (NaNO3) doped graphene nanosheets (GNS). The thermal conductivity of the composite is improved by 245 % with GNS doping ratio of 3.0 wt%, which is due to better phonon vibration matching between GNS and NaNO3. The decrease of phase change enthalpy and melting point are explained from the perspective of mean square displacement. This paper provides a new idea for the selection criteria of the mass fraction of nano-enhancers for molten salt-based PCMs from the perspective of phonon vibration matching.