Sandwich-structured polymer dielectric composite films for improving breakdown strength and energy density at high temperature

Polymer dielectric capacitor have attracted much attention in the field of electronic power systems recently due to high power density and high breakdown strength. However, with the development of miniaturization and integration, further demands have been set on the higher energy storage density as well as better temperature resistance for dielectric polymers. Up to now, hierarchical structure provides an effective way to meet these requirements. Herein, we report a sandwich-structured all-organic composite via inserting polymethyl methacrylate/poly(vinylidene fluoride) (PMMA/PVDF) blend layer into polyetherimide layers. Increasing temperature increases the permittivity of the middle layer and the addition of PMMA makes the permittivity increase faster with temperature than pure PVDF middle layer. The capacitor series model and finite element simulation confirmed that the change of the middle layer permittivity realized the electric field redistribution to self-adapt to the temperature, preventing premature breakdown at elevated temperature. At 100 degrees C, optimized composite exhibits a high breakdown strength of 486.05 MV/m along with high polarization. Eventually, a high discharge energy density of 8.65 J/cm3 is obtained, which is 229.44% of pure PEI. The high polarization at high temperature was realized by utilizing the permittivity of PMMA/PVDF rising with temperature, thereby increasing the energy density at elevated temperature.

Automated summary

Polymer dielectric capacitors have been widely studied in electronic power systems due to their high power density and high breakdown strength. However, the demand for higher energy storage density and better temperature resistance in dielectric polymers has increased with the development of miniaturization and integration. In this study, a sandwich-structured all-organic composite was fabricated by inserting a PMMA/PVDF blend layer into polyetherimide layers. The composite exhibited improved permittivity and energy storage density at elevated temperatures, leading to a high breakdown strength and polarization. The findings suggest the potential of hierarchical structured polymer dielectric capacitors for high-temperature applications.