Superior discharge energy density and efficiency in polymer nanocomposites induced by linear dielectric core–shell nanofibers

For superior performance capacitors, large discharge energy density along with high discharge efficiency, high power density, and ultrafast charging/discharging speed are desired. Herein, we design and prepare new high quality nanocomposite films containing linear dielectric core–shell SrTiO3@Al2O3 nanofibers (ST@AO NFs) and poly(vinylidene fluoride) (PVDF) demonstrating remarkable energy storage performance. The experimental and finite element simulation results suggest that the incorporation of amorphous AO between the ST NFs and PVDF matrix could effectively improve the electric field strength, electric potential distribution, and current density of the nanocomposite films, resulting in greatly enhanced energy density and discharge efficiency. More importantly, the nanocomposite films loaded with 5 vol% ST@AO NFs show an outstanding discharge energy density of 15.3 J cm−3 at 475 MV m−1 and maintain a high discharge efficiency of 68.52%. Moreover, the corresponding nanocomposite films illustrate an ultra-fast discharge rate of 127 ns. The promising overall dielectric properties offer a new insight into the development of next-generation dielectric capacitor materials.