Scalable all-polymer dielectric films with aligned structures for high-temperature energy storage applications

The pursuit of high-temperature dielectric polymers with superior energy density is a critical objective in the development of advanced electronic and electrical systems. However, existing polymers capable of operating at elevated temperatures often suffer from a low dielectric constant and excessive conduction loss. Herein, we present an all-polymer composite with exceptional high-temperature energy storage performance, wherein polyvinylidene fluoride (PVDF) nanofibers are precisely aligned within a polyetherimide (PEI) matrix. The PEI/PVDF composites exhibit an enhanced dielectric constant compared to PEI due to the intrinsically higher dielectric constant of the PVDF component and interface effects between PEI and PVDF components. Moreover, the alignment of PVDF nanofibers achieves a perpendicular orientation to the applied electric field, contributing to enhanced breakdown strength. The resultant PEI/PVDF composites with optimized content and diameter of PVDF nanofibers in the PEI matrix achieve a discharge energy density of 9.39 J cm−3 at 150 °C with the energy efficiency (η) exceeding 90%. This research presents a simple, economical, and scalable method for producing dielectric polymer films with excellent energy storage capacity at high temperatures.