Glutaric acid/expanded graphite composites as highly efficient shape-stabilized phase change materials at medium-temperature

Interest in phase change materials (PCMs) in the medium-temperature range has recently gained significant attention due to their economic benefits and environmental sustainability. This study focuses on investigating the thermal properties of glutaric acid/expanded graphite shape-stabilized phase change materials (GA/EG SSPCMs) prepared by varying GA contents. The morphology, porosity, crystal structure, and chemical and thermal reliability of the prepared SSPCMs were characterized using a range of instrumental analyses. Given a high porosity, EG porous network can confine and stabilize up to 85 wt% GA without leakage, while maintaining the excellent crystallinity of the PCM, due to the capillary and surface tension forces. The SSPCMs exhibited high latent heat storage capacities of up to 167 J/g and crystallization fraction of up to 96.8 %. Interestingly, the SSPCMs effectively suppressed the supercooling degree of GA to below 5 degrees C, making them ideal for practical applications due to the shifts in both the melting and solidification temperatures. The SSPCMs also showed a significant enhancement in thermal conductivity and heat charge/discharge rates compared to the pure GA. Finally, the thermal reliability and stability of the 85 wt% GA/EG SSPCM were confirmed after 300 accelerated thermal cycle tests, making them a promising candidate for long-term applications in medium-temperature thermal energy storage.