Polymer-agnostic crosslinking enables robust high-temperature dielectrics for energy storage

Capacitive energy storage under high operating temperatures and electric fields exceeds the limits of most commercial polymers. While crosslinking can, in principle, enhance electro-thermal stability of polymers, conventional approaches remain severely constrained by their reliance on polymer-specific chemistries and often introduce defects that compromise insulation. Herein we present a polymer-agnostic crosslinking platform based on nitrene-mediated C–H insertion, enabling substantial performance and stability improvement across chemically diverse commercial dielectric polymers. Using polyetherimide as a benchmark, the crosslinked film delivers a discharged energy density of 6.0 J cm−3 with >90% efficiency at 200 °C, along with robust cycling stability ( > 1 × 105 cycles) under harsh operational conditions (at 500 MV m−1) and a projected service lifetime of 60 years under standard industrial fields. This work establishes a facile and practical pathway to upgrade existing industrial polymers for reliable operation under harsh environments. In capacitive energy storage systems, crosslinking can improve polymer electrothermal stability, but conventional approaches rely on polymer-specific chemistries and often introduce defects that compromise insulating performance. Here the authors present a polymer-agnostic crosslinking platform based on nitrene mediated C–H insertion that improves performance and stability across a wide range of commercial dielectric polymers.