Graphene aerogel is widely utilized as a supporting material for latent heat thermal energy storage (LHTES) applications, since the three-dimensional (3D) interconnected structure can hold the working materials. In this work, the mechanical properties and flexibilities of the graphene aerogel were enhanced to reduce the volume shrinkage of phase change material (PCM) composites while the material melts and is infiltrated. For this, polydimethylsiloxane (PDMS) was introduced to the aerogel by solution spray treatment. Because the latent heat (ΔH) is proportional to the PCM weight, the volume shrinkage can influence the thermo-electric energy conversion efficiency. The PDMS-embedded in graphene aerogel significantly enhanced the mechanical property and dimensional stability. Finite element simulation was carried out for comparison with the experimental result.