High temperature energy storage and release properties of polyimide nanocomposites simulated by considering charge trapping effects

Dielectric energy storage capacitors with excellent high temperature resistance are essential in fields such as aerospace and pulse power. However, common high-temperature resistant polymers such as polyimide (PI) and polyether sulfone have low energy storage densities and energy efficiencies at high temperature, which are greatly limited in practical applications. The polymer nanocomposites prepared by doping modification can regulate the charge injection and transport process, and improve the high-temperature energy storage performance. However, the quantitative relationship between charge injection and charge trapping and the energy storage performance of linear polymer nanocomposites still needs further study. An energy storage and release model considering the charge trapping effects is constructed by the authors. We simulate the high-temperature energy storage properties of polyimide nanocomposite dielectrics (PI PNCs) with different charge injection barriers and trap parameters at 150°C. A triangular voltage is applied to the electrodes at both sides of the PI PNCs, the electric displacement-electric field loop is simulated, and the discharged energy densities and energy efficiencies are calculated. The simulation results are consistent with the experimental results. Increasing the charge injection barrier, deep trap energy and deep trap density can effectively reduce the charge injection and the carrier mobility, thereby improving the discharged energy densities and energy efficiencies of dielectric capacitors. In the case of low charge injection barrier (1.3 eV), with the increase of deep trap energy (0.7–1.5 eV) and deep trap density (1 × 10²¹–1 × 10²⁵ m⁻³), the discharged energy density changes from 0.20 to 1.44 Jcm⁻³, the energy efficiency changes from 9.0% to 99.9%, and the high-temperature energy storage performance improves significantly. This research provides theoretical and model support for the improvement of the high-temperature energy storage performance of nanocomposites.