Molecular interface regulation enables order-disorder synergy in electrocaloric nanocomposites

High thermal conductivities are highly desired for electrocaloric (EC) materials to improve the key performances of EC devices, including cooling power density (CPD) and coefficient of performance (COP). However, despite the large EC effect (ECE), the state-of-the-art EC polymer exhibits low thermal conductivity. The simple mixture of the EC polymer and two-dimensional (2D) high-thermal-conductivity nanofillers would dramatically reduce ECE by increasing long-range ordering. To free dipole orientations, we introduced 3-sulfurouspropyltrimethoxysilane (SPTMS) to covalently graft boron-nitride nanosheets on the EC polymer. The interface-regulated nanocomposite exhibited the EC entropy change of 30.94 Jkg-1K-1 under 100 MVm-1 and thermal conductivity of 0.72 Wm -1K-1, and utilizing which, the standard model of EC refrigerator achieved a 5.23 Wg-1 CPD, 6.8-fold higher than the one operating a simple mixture. A figure of merit of electrocaloric nano composites was proposed to assess their overall capability in the heat pumping applications.