Poly(ether imide)-Based Composites with Ultrahigh Energy Storage Capability and Thermal Stability

The polymer dielectric is a promising material for intelligent and energy-saving applications in modern electronic and power systems. However, there are many crucial drawbacks in the applications at elevated temperatures, such as high dielectric loss and low energy density. Herein, a method to enhance the thermal stability of the polymer dielectrics is presented, whereby SrTiO3 particles are introduced into poly(ether imide) (PEI) film to fabricate polymer-based dielectric composites. SrTiO3 is preferred as the filler for its moderate dielectric constant and wide band gap, which simultaneously restrains the leakage current density of the composites. The results show that the composite dielectric loaded with 3 vol % SrTiO3 particles achieves a discharge energy density of 11.30 J/cm3 at 640 MV/m. Furthermore, it exhibits the highest energy density of 10.30 J/cm3 at 150 °C and 530 MV/m, while the discharge energy density and efficiency remain 8.82 J/cm3 and 80% under 500 MV/m at 150 °C, respectively. The composites exhibit excellent fatigue resistance, and the discharge energy density is maintained at 96.21% with an efficiency of 95.96% after 105 charge–discharge cycles at 150 °C. This work elaborates the feasibility of adding SrTiO3 particles into PEI to enhance high-temperature capacitive properties and the great potential for extensive industrial production.