Simultaneously increased discharged energy density and efficiency in bilayer-structured nanocomposites with AgNbO3 lead-free antiferroelectric nanofillers

Abstract

Inorganic ferroelectric/polymer nanocomposite based dielectric capacitors possess fast charge/discharge rates, but they deliver low discharged energy density (U_e) and charge–discharge efficiency (η) due to the large remnant electric displacement (D_r), limiting their use in modern integrated electronic devices. In this study, AgNbO₃ (AN) lead-free antiferroelectric (AFE) nanoparticles (NPs) with near-zero D_r and large D_max are added into poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) polymers to suppress D_r and improve D_max of the nanocomposites. Furthermore, polyimide (PI)–AN NPs/P(VDF-HFP) bilayer nanocomposites are designed and fabricated by adding a linear PI layer with low dielectric constant and high η to improve the interface polarization and make the D–E loops slimmer. Consequently, benefiting from a large E_b of 4504 kV cm⁻¹, high D_max of 7.06 μC cm⁻², high D_max − D_r of 6.52 μC cm⁻² and low dielectric loss of 1%, the PI–5 wt% AN NPs/P(VDF-HFP) bilayer nanocomposites exhibit simultaneously a large U_e of 13.77 J cm⁻³ and high η of 86.87%, outperforming recently reported dielectric nanocomposites in terms of overall energy storage properties. Finite element simulations demonstrate that the introduction of the PI layer causes redistribution of the applied electric field, which restrains the growth of electrical trees at the interfaces of PI and AN NPs/P(VDF-HFP) layers, resulting in a significant enhancement of the E_b. This work refutes the notion that large U_e and η cannot be achieved simultaneously in one kind of nanocomposite and sheds light on developing environmentally friendly dielectric capacitors applicable in modern pulse power systems.