Ultrahigh charge-discharge efficiency and enhanced energy density of the sandwiched polymer nanocomposites with poly(methyl methacrylate) layer

Dielectric materials with ultrahigh energy densities are of importance in modern electric industry. However, for dielectric nanocomposites, their ultrahigh energy densities were typically achieved at the expense of low charge-discharge efficiencies (η) of 60%–70% at high electric fields, which is not desirable for practical applications. In this study, a class of newly designed sandwiched polymer nanocomposites based on poly(methyl methacrylate) (PMMA) as the central layer to enhance the breakdown strength and charge-discharge efficiency and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) loaded BaTiO₃ nanoparticles (BT NPs) as the outer layers to boost the polarization. It is found that the sandwiched nanocomposite with 10 wt% BT NPs in the outer layers possesses a largely enhanced energy density of 17.1 J cm⁻³ with a high η of 82% at the Weibull breakdown strength of 559 MV m⁻¹. To our knowledge, this is one of the highest η achieved at high electric fields among the dielectric nanocomposites reported so far. This work demonstrates the uniqueness of the trilayered structure to incorporate multiple components and display much enhanced collective properties for energy applications.