Enhancement of Energy Storage Performance in Polymer Dielectrics via Monodisperse ZrO2 Nanoparticles as Nanofiller

Abstract Polymer dielectric capacitors are known for their high‐power density and rapid charge–discharge rates, which makes them widely used in electric power systems. However, their low energy density limits their application in advanced energy storage devices. Incorporating nanosized inorganic fillers into the polymer matrix has proven effective in increasing the dielectric constant of polymers, but compromises the breakdown strength and energy storage density due to the incompatibility between the fillers and matrix. Interfacial modification can address these issues to some extent, but challenges remain in developing individually dispersed nanofillers, particularly those that are universally compatible with both polar and nonpolar polymers. In this study, a novel nanofiller, monodisperse ZrO 2 nanoparticles is introduced, which enhances the breakdown strength and energy density of two different polymer matrices, including polyetherimide and polypropylene. These nanoparticles are functionalized with trioctylphosphine oxide surfactant, preventing particle aggregation and improving compatibility with the polymer matrices. The uniformly dispersed ZrO 2 nanoparticles act as scattering centers, inhibiting the transfer of charge carriers within the polymer matrices, thus enhancing both breakdown strength and energy density. This approach offers a new strategy for improving the energy storage density of polymer dielectric capacitors, applicable to both polar and nonpolar polymer matrices.