Significantly enhancing the discharge efficiency of sandwich-structured polymer dielectrics at elevated temperature by building carrier blocking interface

Dielectric materials with high power densities have irreplaceable advantages in electrical energy storage. However, conventional polymer dielectrics are unable to meet the ever-increasing power demands in harsh environments. Here we report a high-temperature dielectric based on judiciously designed all-polymer sandwiched films consisting of polyimide (PI) and polyetherimides (PEIs). Due to the swelling effect of PEIs solution on the PI surface, it built a clear and complete interface with a gradient change molecular stacking structure between the PEIs and PI layers in the sandwiched film, resulting in an increase in the density of deep traps and the accumulation of space charges in the interface. It is found via direct experimental evidence that the high-field electrical conduction at high temperatures can be effectively suppressed. The sandwiched film exhibits excellent comprehensive capacitive performance even at 200 °C, e.g. a discharged energy density of 2.0 J cm⁻³ and a charge-discharge efficiency of 92% at 300 MV m⁻¹. Along with facile technology compatible with roll-to-roll processing, this work also opens a new avenue to high-energy-density all-polymer dielectric for high-temperature applications by building interface carrier barrier.