The Enhancement of Thermophysical and Encapsulation Properties of Erythritol-Based Composite Phase Change Materials Through Oxidative Modification of Expanded Graphite

Erythritol (ER) exhibits competitive advantages for medium-low temperature thermal energy storage due to its high melting enthalpy (340–360 J/g), low cost, and appropriate phase transition temperature. Compounding with high thermal conductivity carbon materials is effective in overcoming the low thermal conductivity of the phase change materials (PCMs). This study aims to enhance the thermal conductivity and encapsulation performance of PCMs by improving the compatibility between expanded graphite (EG) and ER. The results demonstrate that hydrogen peroxide oxidation introduces oxygen-containing functional groups on EG surfaces, enhancing the affinity between hydrophilic EG (HEG), and ER. The thermal conductivity of the HEG-ER composites PCMs containing 1–5 wt % HEG reached 2.584–5.824 W/m·K, showing a 4.998% improvement at least compared to the EG-ER composites at equivalent EG loadings. After heating for 60 min, the leakage rates for HEG-ER composite PCMs containing 1–5 wt % HEG were 4.719%–0.802%, compared with the EG-ER composite PCMs with the same quality fraction of EG, the maximum reduction is 54.393%. The melting enthalpy of HEG-ER remained above 320 J/g, exhibiting excellent stability after 100 thermal cycles. This study provides a theoretical guidance for the development of sugar alcohol-based PCMs with high thermal conductivity and encapsulation performance.