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., Delta T/Delta E and Delta S/Delta E, where Delta T is the adiabatic temperature change, Delta E is the applied field change, and Delta S 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 Delta T=5.2 K and Delta S=24.8 J kg(-1) K-1 under 40 MV m(-1), generating a large electrocaloric coefficients of Delta T/Delta E=0.13 x 10(-6) km V-1 and Delta S/Delta E=0.62 x 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. (C) 2016 Elsevier Ltd. All rights reserved.