Atomic-scale interface engineering in BaTiO3@TO2 nanofibers (TiO2 nanofibers embedded with BaTiO3 nanoparticles) leads to concurrent enhancement of electric displacement and breakdown strength in poly(vinylidene fluoride) (PVDF)-based nanocomposites. An ultrahigh energy density of approximate to 20 J cm-(3) is achieved with only 3 vol% nanofibers, which is by far the highest discharged energy density of PVDF-based nanocomposites.