Introducing the SiO2@mesoporous SiO2@Ag nano-hybrids to regulate the energy storage performance of composite dielectrics

Polymer-based dielectric capacitors are crucial for electronics and electric power systems due to their ultrahigh power density. However, the low energy density of polymer-based dielectrics becomes one critical shortcoming that severely limiting their practical application range. Herein, a typical surface-modified poly(vinylidene fluoride) (PVDF)-based composite dielectric with excellent energy storage property is presented. In order to construct a structurally-stable metal-dotted functional unit, a type of special Ag-dotted mesoporous silica-coated silica (SiO 2 @mSiO 2 @Ag) nanoparticles with core-satellite structure is designed. In this nano-architecture, the Ag nanoparticles can be tightly fixed in the porous shell and isolated from each other by the wedge-shape of SiO 2 @mSiO 2 nano-substrates. Both the micro-capacitance structure and Coulomb-blockade effect that induced by the Ag nanoparticles can effectively improve the permittivity, breakdown strength and the overall energy storage property of the composite dielectric. Moreover, the surface defects of composite dielectric can be partially modified by using polymethyl methacrylate (PMMA) ultrathin outer layers. Benefiting from these regulations to both the electrode-dielectric interface and nano-structure of functional unit, an excellent energy density of 13.8 J/cm 3 at the high electric field of 534.1 MV/m is obtained from the PVDF-based composite incorporated with as small as 0.5 wt% SiO 2 @mSiO 2 @Ag nanoparticles. This study provides an effective strategy for the development of polymer-based film capacitors with an advanced energy storage property.