Enhanced high-temperature energy storage in semi-aromatic polyimides via dual regulation of short-range ordered and crosslinked architectures

Abstract

Polymer-based dielectric capacitors for extreme environments require materials with exceptional electrical insulation. Polyimide (PI) is a promising candidate for high-temperature energy storage, yet it suffers from charge transfer complexes (CTCs) formation under high temperatures and electric fields, compromising its insulation performance. Addressing this critical limitation, our study presents an innovative molecular engineering strategy that simultaneously regulates the short-range ordered structure and crosslinking density within a semi-aromatic polyimide (SAPI) framework. By optimizing imidization temperatures and integrating ethyl side chains into the polymer architecture, we achieved molecular-level control that not only reduces energy losses but also significantly elevates energy storage capabilities under extreme conditions. Notably, the modified SAPI (E-SAPI) demonstrated discharge energy densities (U_d) of 8.61 J cm⁻³ at 150 °C and 6.50 J cm⁻³ at 200 °C, with efficiency (η) exceeding 90%, positioning it among the top-performing materials in the field. Even at 250 °C, near its glass transition temperature, E-SAPI maintained a high U_d of 3.94 J cm⁻³, showcasing exceptional insulation and resistance to catastrophic failure. This approach reveals a new paradigm for designing high-performance dielectric materials, potentially transforming the future of energy storage in harsh environments.