Giant barocaloric effects in composites of ethylene vinyl acetate copolymers and multilayer graphene with improved thermal conductivity

Elastic polymers with large and reversible barocaloric effects over wide temperature ranges are of potential application in solid-state refrigeration. However, the low thermal conductivity is harmful for their practical performance in a solid-state cooling device. In this work, an appropriate amount of multilayer graphene was incorporated into the polymer matrix to fabricate composites. Compared to the original material, an ethylene vinyl acetate copolymer, the thermal conductivity was increased for several times, while the reversible giant barocaloric effect over a wide temperature range, the excellent elastic deformability and the so-called self-pressure-transmission characteristics were largely preserved. The composite with a 16.7% mass fraction of multilayer graphene exhibits an increased thermal conductivity from 0.27 to 1.02 W/mK and an adiabatic temperature change of 23.6 K at room temperature during the rapid compression and decompression of 400 MPa, demonstrating well-balanced performances as a solid-state refrigerant. Our results can promote the study of elastic polymers with giant barocaloric effects and facilitate their practical application in the field of solid-state cooling.