Improved energy storage performance of nanocomposites with Bi_(4.2)K_(0.8)Fe_(2)O_(9+δ) nanobelts

Modern electronics and electric power grids require high performance polymer-based dielectric nanocomposites.To realize large-scale applications,the energy density of nanocomposites needs to be further increased.Here,we demonstrate a remarkable improvement in energy density of poly(vinylidene fluoride)(PVDF)matrix upon the incorporation of high-k Bi_(4.2)K_(0.8)Fe_(2)O_(9+δ)(BKFO)nanobelts.High aspect ratio BKFO nanobelts can enhance the Young's moduli of the nanocomposites and increase the path tortuosity of electrical trees,which are favorable for increasing the breakdown strength of the system.Thus,the dielectric constant and breakdown strength increase simultaneously at a low volume fraction(0.35 vol%)of BKFO nanobelts,and an ultrahigh recoverable energy density of 25.4 J/cm^(3) is achieved.These results provide a strategy to develop high performance flexible high-energy-density devices.