Graphene enabled percolative nanocomposites with large electrocaloric efficient under low electric fields over a broad temperature range

For practical electrocaloric (EC) cooling devices, besides a large electrocaloric effect (ECE), the EC coefficients, e.g., δT/δE and δS/δE, where δT is the adiabatic temperature change, δE is the applied field change, and δS is the isothermal entropy change, are equally or even more important. An EC material with a large ECE and large EC coefficients will lead to practical EC cooling devices with high reliability. Here, we investigate a graphene enabled percolative relaxor polymer nanocomposite in order to address the challenge of how to generate a practically usable electrocaloric effect (ECE) under low electric field. We show that, through a proper fabrication process, the nanocomposites can reach a δT=5.2 K and δS=24.8 J kg^-1 K^-1 under 40 MV m^-1, generating a large electrocaloric coefficients of δT/δE=0.13×10^-6 km V^-1 and δS/δE=0.62×10^-6 J m kg^-1 K^-1 V^-1. The work here indicates the promise of the percolative nanocomposite approach with graphene nanofillers to achieve a highly efficient and large ECE in the EC polymers for practical EC cooling.