Enhancing breakdown strength and energy storage performance of PVDF-based nanocomposites by adding exfoliated boron nitride

Polymer/ceramic nanocomposites are promising dielectrics for high energy storage density (U _e ) capacitors. However, their low breakdown strength (E _b ) and high dielectric loss due to heterogeneous structure seriously limit their applications under high electric field. In this work, boron nitride nano-sheets (BNNS) exfoliated from BN particles were introduced into PVDF-based BaTiO ₃ (mBT) binary composites to reduce the dielectric loss and promote the U _e . The effects of BNNS on the dielectric properties, especially breakdown resistance, and energy storage performance of the resultant composites were carefully investigated by comparing with the composites without BNNS. The introduction of BNNS could significantly improve E _b and U _e of the final composites. Ternary composite with particle contents of 6 wt% BNNS and 5 wt% mBT presented a E _b of about 400 MV/m and U _e of 5.2 J/cm ³ , which is 40% and 30% superior to that of the binary composite with 5 wt% mBT, respectively. That may be attributed to the 2D structure, high bulk electrical resistivity, and fine dispersion in PVDF of BNNS, which is acting as an efficient insulating barrier against the leakage current and charges conduction. The depression effect of BNNS onto the charge mobility and the interfacial polarization of the polymer composites is finely addressed, which may offer a promising strategy for the fabrication of high-k polymer composites with low loss.