Improved energy storage performance of sandwich-structured P(VDF-HFP)-based nanocomposites by the addition of inorganic nanoparticles

With the rapid development of the modern electronic and electrical industry, dielectric capacitors with higher energy storage capacity have become in urgent demand in the application market. Although polymer-based composites have great application potential due to their advantages of easy machining, good self-healing and low cost, their ability to store energy is nevertheless severely constrained by the negative relationship between the polymers' breakdown strength and permittivity. In this study, we designed sandwich-structured nanocomposites, where the interlayer is filled with 0.85K_0.5Na_0.5NbO₃-0.15Bi(Zn_2/3Ta_1/3)O₃ nanoparticles (KNN-BZT NPs) while the outer layer is P(VDF-HFP). The design of this structure resolves the contradiction between high breakdown strength (E_b) and dielectric constant (ϵ_r), making it a helpful tool for enhancing the energy storage performance. The experimental results show that when the filler content of KNN-BZT NPs is 0.6 vol%, the E_b reaches 565.44 MV m⁻¹, and the maximum and residual electric displacement obtained are 10.43 μC cm⁻² and 1.26 μC cm⁻², respectively. Meanwhile, the optimal discharge energy density (U_d) and efficiency (η) are 21.39 J cm⁻³ and 70.54%, respectively. These values are 2.77 and 1.27 times higher than those of P(VDF-HFP). The sandwich-structured nanocomposites provide an economical and efficient strategy for increasing the ability of film capacitors to store energy.