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., Δ T /Δ E and Δ S /Δ E , where Δ T is the adiabatic temperature change, Δ E is the applied field change, and Δ 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 Δ T =5.2 K and Δ S =24.8 J kg −1  K −1 under 40 MV m −1 , generating a large electrocaloric coefficients of Δ T /Δ E =0.13×10 −6  km V −1 and Δ S /Δ E =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.