Enhanced energy density with high efficiency in epoxy-based capacitor films with steering TiO₂ nanowires

The energy storage can't be separated from the capacitor films with high energy density and charge-discharge efficiency. In this study, TiO₂ nanowires were synthesized via hydrothermal reaction, and epoxy based nanocomposite films were prepared by hot pressing. Simultaneously, electric field was applied to induce the steering of nanowires. The introduction of nanowires improved the energy density due to the increased permittivity but at the expense of the efficiency and breakdown strength. Improved breakdown strength was achieved through the steering of nanowires. Additionally, the steering promotes the charge-discharge efficiency at the mass fraction of 0.5% and 1%, due to the decrease of dielectric loss. While the function of steering at 2% mass fraction is to further rise the dielectric permittivity. Therefore, a large discharge energy density of 5.77 J/cm³ with an efficiency of 80% is achieved at 510 MV/m in the nanocomposites containing 2wt% steering nanowires. The epoxy-based nanocomposite films have the potential to become an alternative of capacitor films. And the electric assisted steering could be an effective approach to handle the paradox of increased permittivity with decreased efficiency and breakdown strength.