Ultra-high energy density integrated polymer dielectric capacitors

Abstract

Flexible dielectric polymers with high energy storage density are needed for film capacitor applications including hybrid electric vehicles and medical apparatuses. Poly(vinylidene fluoride) (PVDF) is regarded as a promising candidate owing to its intrinsic high polarisation, outstanding processability, good mechanical properties, and high dielectric breakdown strength. However, normal PVDF suffers from low energy density (Ue) and charge-discharge efficiency (η) at high electric fields. In this study, these restrictions are successfully overcome using a novel facile one-step Roll & Press method. A record high energy storage density of 50.2 J cm−3 with an outstanding charge-discharge efficiency of 80% is achieved at 1000 kV mm−1 in relaxor-like PVDF, which is ascribed to reversible polar nanostructures generated by the constraining effect originating from continuous folded boundaries in the multilayer structure during rolling and pressing. The superior energy storage performance of Roll & Pressed PVDF surpasses those of all other polymer-based materials reported. Additionally, a ready-to-use capacitor is assembled using the Roll & Press technique with electrodes constructed using a stretchable carbon nanotube veil (CNT veil), which exhibits strong interfacial interactions with the PVDF film and results in excellent energy storage performance. The universal applicability of the Roll & Press method and superior energy storage properties makes PVDF a strong candidate for modern energy storage systems.