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

Inorganic ferroelectric/polymer nanocomposite based dielectric capacitors possess fast charge/discharge rates, but they deliver low discharged energy density (Ue) and charge–discharge efficiency (η) due to the large remnant electric displacement (Dr), limiting their use in modern integrated electronic devices. In this study, AgNbO3 (AN) lead-free antiferroelectric (AFE) nanoparticles (NPs) with near-zero Dr and large Dmax are added into poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) polymers to suppress Dr and improve Dmax 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 Eb of 4504 kV cm−1, high Dmax of 7.06 μC cm−2, high Dmax − Dr 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 Ue 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 Eb. This work refutes the notion that large Ue 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.