Dielectric nanocomposites with high energy density by doping core-double shell structured fillers

Dielectric capacitors consisting of ceramic/polymer nanocomposites have been widely used in electrical and electronic fields due to the advantages of high power density, high stability and improved energy density. However, the mismatching of dielectric constant between ceramics and polymers seriously limits the improvement of energy density of dielectric capacitors. In this work, a novel kind of core-double shell structured ceramic filler BaTiO3@TiO2@SiO2 (BT@TO@SO) is prepared by a two-step hydrolysis method and introduced into PVDF for high performance dielectrics. This core-double shell structured filler forms multi-layer interface with gradually reduced dielectric constants of BT, TO, and SO, which is beneficial to enhance the interface polarization and reduce the electric field concentration caused by dielectric mismatch. In addition, the high insulating properties of the outer layer of SO can greatly limit the electron migration and reduce the leakage current. The experimental results show that when the loading of BT@TO@SO filler is low, the nanocomposite can achieve an energy density of up to 19.7 J/cm3 and an efficiency of 57.6% at 620 MV/m, which shows an obvious improvement compared with filling BT or BT@SO. The results of finite element analysis further verify the superiority of this core-double shell structure.