Scalable Polymer Nanocomposites with Record High‐Temperature Capacitive Performance Enabled by Rationally Designed Nanostructured Inorganic Fillers

Next-generation microelectronics and electrical power systems call for high-energy-density dielectric polymeric materials that can operate efficiently under elevated temperatures. However, the currently available polymer dielectrics are limited to relatively low working temperatures. Here, the solution-processable polymer nanocomposites consisting of readily prepared Al₂ O₃ fillers with systematically varied morphologies including nanoparticles, nanowires, and nanoplates are reported. The field-dependent electrical conduction of the polymer nanocomposites at elevated temperatures is investigated. A strong dependence of the conduction behavior and breakdown strength of the polymer composites on the filler morphology is revealed experimentally and is further rationalized via computations. The polymer composites containing Al₂ O₃ nanoplates display a record capacitive performance, e.g., a discharged energy density of 3.31 J cm^-3 and a charge-discharge efficiency of >90% measured at 450 MV m^-1 and 150 °C, significantly outperforming the state-of-the-art dielectric polymers and nanocomposites that are typically prepared via tedious, low-yield approaches.