Enhancing energy density of dielectric polymer nanocomposites at ultralow filler loadings

Dielectric polymer nanocomposites have been extensively studied to achieve high-energy-density capacitors. However, their energy density ( U d ) usually improves at the expense of transparence, light weight, and processibility of polymer matrices because of high nanofiller loadings. Herein, polydopamine-modified titanoniobate nanosheets (TNO@PDA_nss) were prepared as fillers. Their high relative permittivity ( ε r ) contributes to increasing ε r . Their large aspect ratio facilitates to improve the mechanical properties and distort the electrical treeing paths. Moreover, they are negatively charged and can electrostatically block energetic electrons. Thus, ε r and breakdown strength of the polymer nanocomposites simultaneously enhance at ultralow filler loadings, leading to significantly enhanced U d . The 0.2 wt% TNO@PDA_nss/PVDF/PMMA nanocomposites exhibit a maximum U d of 11.5 J/cm 3 , which is 2.1 and 1.5 times that of pristine PVDF and PVDF/PMMA blend, respectively. This work presents a facile strategy that hardly compromises the advantages of polymer matrices to obtain high- U d polymer nanocomposites at ultralow filler loadings.