Low-content core–shell-structured TiO2 nanobelts@SiO2 doped with poly(vinylidene fluoride) composites to achieve high-energy storage density

Polymer film capacitors have a high power density and great application potential in high-power electronic devices; however, high-energy storage density of polymer composites is usually obtained via doping high-content ceramic filler. An efficient approach to solve this issue is to dope polymers with an ultralow-content ceramic filler to improve their energy storage density. In this work, one-dimensional (1D) TiO 2 nanobelts@SiO 2 (TO nb@SO) are prepared via the hydrothermal reaction, muffle calcination, and hydrolysis. Extremely low-content TO nb@SO/poly(vinylidene fluoride) (TO nb@SO/PVDF) composites are prepared. The microstructure, crystalline structure, dielectric properties, electric breakdown strength, and discharge energy density are systematically investigated. The results show that the nanobelts have a width of 250 nm, a length of 1–2 μm, and a uniform shell layer at the edge with a thickness of ∼25 nm. The relative dielectric constant of the composites is significantly enhanced; it reaches 11 for PVDF at 100 Hz, and 12.03 for 0.5 wt% TO nb@SO/PVDF. The theoretical dielectric constant is calculated based on a mathematical model and compared with the measured value. 1D materials with a large aspect ratio are beneficial in the improvement of the dielectric properties. The Weibull breakdown field strength is 381.3 MV/m for 0.5 wt% TO nb@SO/PVDF. A discharge energy density of 8.86 J/cm 3 is obtained at 390 MV/m, while a high charge/discharge efficiency of 66.28% is achieved. To conclude, this work provides a valuable method for increasing the energy storage density and charge/discharge efficiency of dielectric capacitors.