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Enhancing discharged energy density and suppressing dielectric loss of poly(vinylidene fluoride‐ter‐trifluoroethylene‐ter‐chlorofluoroethylene) by a sandwiched structure

Polymer dielectrics with high energy density and low dielectric loss are highly desired due to the rapid development of electric devices. Among known polymers, poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorofluoroethylene) P(VDF-TrFE-CFE) is one of the promising materials for energy storage capacitor applications because of its high dielectric constant. Nevertheless, it suffers from high dielectric loss especially at the high electric field, which suppresses its breakdown strength and energy storage density. Herein, sandwiched structure dielectric films were fabricated by employing polymethyl methacrylate (PMMA) as the outer layer and P(VDF-TrFE-CFE) as the central layer. By modulating the thickness of the central layer, an enhanced discharged energy density of 7.03 J/cm3 is achieved at a high electric field of 480 MV/m, which is 132% more than that of P(VDF-TrFE-CFE) at its maximum electric field 300 MV/m. Meanwhile, this sandwiched structure film also retains a high discharge efficiency of 78% at 480 MV/m, which is never been seen in polyvinylidene fluoride-based polymers. Results show that PMMA acts as charge barrier and simultaneously enhance the breakdown strength and suppress the dielectric loss of P(VDF-TrFE-CFE).