Ultrahigh discharge efficiency and energy density achieved at low electric fields in sandwich-structured polymer films containing dielectric elastomers

Dielectric polymer capacitors, especially those capable of operating efficiently at relatively low operating voltages, are urgently needed to meet the growing demands for miniaturization and reliability in advanced electronics and electrical power systems in automobiles and aerospace. However, high-performance energy storage properties are normally obtained in dielectric capacitors under the application of high electric fields. Herein, a series of all-polymer sandwich-structured films comprised of acrylic rubber dielectric elastomers (DE) dispersed in ferroelectric poly(vinylidene fluoride-cohexafluoropropene) as the outer layer and poly(methyl methacrylate) as the middle layer have been fabricated. The maximum electrical displacement, energy density, and discharge efficiency of the sandwiched films have been improved significantly by optimizing the DE content. Notably, a high energy density of 11.8 J cm(-3) along with a very high efficiency of 89% has been achieved in the sandwiched film with 30 wt% DE at an applied field of 300 MV m(-1), which is the best overall property set ever achieved in the representative polymer dielectrics. Excellent power density and great stability of energy storage performance over the bending cycles have been demonstrated in the layered films. All these features offer new opportunities for designing a new class of hierarchically structured dielectric polymers with excellent energy storage capability that can be achieved at relatively low electric fields.