Design of heterogeneous sandwich-structured dielectric composites with excellent charge–discharge efficiency and energy storage density

Abstract

With the rapid development of new energy fields, polymer-based film capacitors have received extensive attention in the field of dielectric capacitors due to their high power density. The nonlinear ferroelectric polymer polyvinylidene fluoride was widely used in the field of dielectric capacitors due to its high dielectric constant and good polarization properties. However, high tan δ (loss angle tangent) and relatively low breakdown strength limit its further development. In this work, a heterogeneous sandwich symmetric composite dielectric was designed. For the composite dielectric, the polarization layer is made of polyvinylidene fluoride blending with an appropriate amount of cyanoethyl cellulose, which effectively enhances the polarization strength of the dielectric composite. The insulating layer is a polyethersulfone-based composite dielectric with significantly improved energy storage and breakdown after doping with a small amount of TiO₂. A composite dielectric with high charge–discharge efficiency and energy storage density was eventually created by changing the distribution of inner and outer layers. Fortunately, the heterogeneous sandwich structured composite dielectric can reach an energy storage density of 14.9 J cm⁻³ at 589 kV mm⁻¹ while the charge–discharge efficiency is as high as 89.9%. The construction of a heterogeneous sandwich structure not only combines the advantages of PVDF and PESU, but also contributes to the optimization of energy storage performance, which drives the development of dielectric materials for capacitors.