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

Abstract

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=5.2K and ΔS=24.8Jkg−1K−1 under 40MVm−1, generating a large electrocaloric coefficients of ΔT/ΔE=0.13×10−6kmV−1 and ΔS/ΔE=0.62×10−6Jmkg−1K−1V−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.