Thermal and photo/electro-thermal conversion characteristics of high energy storage density expanded graphite/polyethylene glycol shaped composite phase change materials

Abstract

Compared with other energy storage materials, phase change materials (PCMs) are drawing widespread attention because of their high enthalpy and low temperature change. However, its low thermal conductivity, low photo/electro-thermal conversion characteristics, phase separation and easy leakage are still urgent problems. In this work, expanded graphite/polyethylene glycol (EG/PEG) composites were prepared based on physical adsorption method, the relationship between the mass percentage of EG and the microstructure, phase transition properties (phase change enthalpy, supercooling degree) and energy conversion properties was studied. The composite PCM exhibits exceptional thermal conductivity (2.48 W·m−1·K−1, 7 folds greater than that of PEG) and outstanding melting enthalpy (161.4 J/g). The thermal conductivity of the EG/PEG composites is almost constant versus temperature over measured temperature range (26 ℃∼60 ℃). The energy conversion capacities (photo/electro-thermal conversion) increase as the expanded graphite mass fraction increases. The prepared composite PCM obviously overcomes the shortcomings of the pure polyethylene glycol, and highlights enormous application in the domains of multi-physical energy conversion and premium quality power absorption.