Ultrahigh High‐temperature Capacitive Energy Storage Via Proton Irradiation

Abstract Polymer‐based film capacitors with ultrafast rates are extensively used in modern electronics and electric power systems. Dielectric polymers typically exhibit a low dielectric constant, while their energy density at elevated temperatures is limited by drastically increased conduction. To address this challenge, it is reported that proton irradiation enables concurrently enhanced dielectric constant and energy storage properties at high temperatures. The combined atomic force microscopy‐infrared spectroscopy and first‐principles calculations reveal that proton irradiation facilitates local rotation of ether bonds in aromatic polymers, producing greatly increased local polar states leading to markedly improved polarizability while preserving dense chain packing. Consequently, an ultrahigh discharged energy density of 6.9 J cm ⁻³ with an efficiency > 95% is achieved in irradiated poly(ether imide) at 150 °C, exceeding current dielectric polymers and nanocomposites. The results suggest an alternative postprocessing method toward rational design of high‐performance dielectrics for capacitive energy storage.