Enhanced Energy Storage Density of Ferroelectric Polymer-Based Composite Dielectrics via Introducing Surface-Charged Kaolin Nanosheets

A dielectric capacitor is one widely utilized basic component in current electronic and electrical systems due to its ultrahigh power density. However, the low inherent energy density of a dielectric capacitor greatly restricts its practical application range in energy storage devices. Being different from the traditional nanofillers, the electrically charged nanofillers can regulate the migration of free charges in dielectrics. Herein, a typically low-cost surface-charged kaolin nanosheet (KLNS) incorporating a poly(vinylidene fluoride) (PVDF)-based composite dielectric is proposed. The KLNS was exfoliated from the bulk kaolin, a kind of natural multilayered mineral which has abundant reserves in the earth. The experimental results exhibited that the addition of KLNS effectively enhanced the breakdown strength of the composite dielectrics because the surface electronegativity of KLNS can tune the kinetic energy of free charges via the electrostatic effect. Consequently, an excellent maximum discharge energy density of 18.2 J/cm3 at a significantly elevated electric field of 530.9 MV/m was obtained from the composite incorporated with as little as 0.2 wt % KLNS, which are 766.7% and 118.2% greater than those of the pristine PVDF matrix (2.1 J/cm3 and 243.3 MV/m), respectively. This research provides a feasible route for the preparation of next-generation composite dielectrics with low cost, ease of processing, and high energy density.