Significantly enhanced high-temperature energy storage capacity for polyetherimide-based nanocomposites via energy level modulation and electrostatic crosslinking

In the field of electrostatic energy storage, polymers exhibit notable advantages, including high breakdown strength (E b ) and fast charge/discharge rates. However, at elevated temperatures, their discharge energy density (U d ) decreases due to reduced E b and increased electrical conductivity losses. We herein integrate fluoro-functionalized polyimide (PFI) shell-modified Al 2 O 3 nanoparticles (PFI@Al 2 O 3 ) with polyetherimide (PEI) to form a trap-rich electrostatic crosslinked network. By energy level modulation and electrostatic crosslinking, the PFI layer enables to capture charges and acts as crosslinking sites, while the wide-bandgap Al 2 O 3 introduces energy barriers that inhibit charge injection and migration. This sophisticated dual-interface design enhances E b and facilitates dual capture of electrons and holes, thus effectively reducing leakage current and conduction losses. Surprisingly, the composites prepared using this method exhibit an energy density of 7.24 J/cm³ at 150 °C, with a charging-discharging efficiency of 83.58 %. Moreover, it maintains stability even after 10 5 extended charge-discharge cycles under harsh conditions (200 kV/mm and 150 °C). This work lays a solid foundation for electrostatic energy storage at elevated temperature.