Ultrahigh Breakdown Strength and Improved Energy Density of Polymer Nanocomposites with Gradient Distribution of Ceramic Nanoparticles

High-energy-density polymer nanocomposites with high-dielectric-constant ceramic nanoparticles as the reinforcement exhibit great potential for energy storage applications in modern electronic and electrical systems. However, the decline of breakdown strength by high loading of ceramic nanoparticles hinders this composite approach from sustainable promotion of energy density. In this work, an approach is proposed and demonstrated by constructing gradient distribution of the spherical ceramic nanoparticles in the polymer matrix. These gradient-structured nanocomposites possess remarkably improved mechanical and electrical behaviors, which give rise to ultrahigh breakdown strength and much-promoted energy density. Moreover, this enhancement effect can be further enlarged via increasing the grades number of gradient structures. This work provides an effective strategy for developing flexible high-energy-density polymer/ceramic nanocomposites for dielectric and energy storage applications.