Phase change materials (PCMs) have limited use in thermal storage because of their poor conductivity and lack of multi driving energy. Therefore, to overcome these problems, polyethylene glycol-calcium chloride/expanded graphite (PEG-CaCl2/EG) functional composite PCMs with high electrical and thermal conductivities were synthesized by ligand substitution using PEG-CaCl2 as the PCM and EG as the highly electrically and thermally conductive framework material. The PEG-CaCl2/EG PCMs were thoroughly investigated, and the experimental results revealed the significance of EG in the composite structure, which leads to high electrical conductivity and high thermal conductivity. The resistivity of the functional PCM decreased to 1.67 omega m, and the thermal conductivity (k) increased to 8.4 W/(m K) when the EG content was 10 wt%. In addition, the electro-thermal conversion efficiency of the functional PCM reached 86.9%, and its energy storage could be inspired at low voltages (2.0-5.0 V). The heating and energy storage rates increased with the working voltage and EG content, respectively. Melting-crystallization experiments and electro-thermal cycle tests showed that the functional PCMs had good thermal stability. Therefore, this study provides a new perspective for various fields of energy conversion and storage.