Remarkably Enhanced Energy Storage Performances in Well-Designed Core–Shell Ag@TiO2–Poly(vinylidene fluoride) Nanocomposites

Designing and regulating the microstructure of core–shell fillers are effective ways to fabricate polymer-based nanocomposites with excellent energy storage performances. Along this line, the unique structure combination of 0D metallic Ag nanoparticles (NPs) and 1D bark-like TiO2 nanowires (NWs) were successfully prepared. Through regulating the volume fraction of Ag NPs (x vol %) in the Ag@TiO2 NWs, the polarization and breakdown strength of Ag@TiO2/PVDF nanocomposites have been optimized, which is evidenced both by the experimental results and finite element simulation. As a result, remarkably enhanced energy storage performances are realized in these nanocomposites. For instance, the 6 vol % Ag@TiO2/PVDF nanocomposite shows an excellent performance of the highest discharged energy density of 16.3 J/cm3 at 376 MV/m, increased by 222% compared with that of pure PVDF (7.4 J/cm3, 335 MV/m). Meanwhile, its charge and discharge efficiency remain up to 77% owing to the reduction of the leakage current density caused by the Coulomb blocking effect of small-sized Ag NPs and the prolonged breakdown path resulted by TiO2 NWs. This proof-of-concept study provides an innovative design thinking of the hybrid structure for obtaining nanocomposites with extraordinary energy storage performances.