Achieving synergistic improvement in dielectric constant and energy storage properties of all-organic liquid crystal molecule/PVDF composites

Abstract

It is an urgent issue to enhance the energy storage capacity of dielectric film capacitors for their miniaturization and integration into lightweight electronic devices under the premise of large-scale industrial production. In this work, via selecting a low-cost liquid crystal small molecule (4-cyano-4′-pentylbiphenyl, denoted as 5CB) as the organic filler, a series of all-organic poly(vinylidene fluoride)-based (PVDF) composite films are prepared through a simple solvent casting method. The 5CB organic filler with high liquid mobility and strong polarity can mix and interact well with the PVDF matrix, thus forming dense and high-quality dielectric polymer films. As a result, the 5 wt% 5CB/PVDF composite exhibits the highest dielectric constant of 9.8 at 1 kHz because of its great dispersibility and strong interfacial polarization. More importantly, a maximum discharge energy density of 11.7 J cm⁻³ is obtained due to the increased crystallinity, the formation of charge traps and enhanced mechanical properties, which is more than 3 times that of a pristine PVDF film (3.8 J cm⁻³). This work is viable for large-scale preparation of high performance flexible dielectric composites via a simple and inexpensive method.