Achieving ultrahigh energy storage density and energy efficiency simultaneously in sodium niobate-based lead-free dielectric capacitors via microstructure modulation

Abstract

Recently, dielectric capacitors have drawn much attention from researchers and engineers due to their ultrahigh power density, ultrafast charge–discharge rate, and good temperature and fatigue stability. However, most related research mainly focuses on the improvement in dielectric breakdown strength and energy storage density rather than that in energy efficiency. In this study, we adopted the spark plasma sintering method to modify the microstructure and electric conductivity of Na_0.7Bi_0.1NbO₃ lead-free ceramics, and subsequently enhanced their energy storage properties. As a result, the Na_0.7Bi_0.1NbO₃ ceramics prepared by the spark plasma sintering method display a considerably large energy storage density of 3.41 J cm⁻³ with an ultrahigh energy storage efficiency of 90.8% at 28 kV mm⁻¹. The improvement of energy storage performance is ascribed to the reduction of electric conductivity, which can be analyzed by the X-ray photoelectron spectroscopy and high-temperature complex impedance spectra. This study not only paves the way for environment-friendly Na_0.7Bi_0.1NbO₃ lead-free ceramics to be developed for energy storage applications, but also interprets the internal mechanism of microstructure modulation which enhances energy storage properties.