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

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 46; pp. 17757 - 17767
• Main Authors: Liu, Xuan, Luo, Huang, Yan, Chuanfang, Liu, Yuan, Luo, Hang, Zhang, Dou, Chen, Sheng
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.12.2022
• Subjects: Composite materials; Electronic devices; Energy storage; Fillers; Liquid crystals; Mechanical properties; Miniaturization; Organic liquids; Permittivity; Polymer films; Polyvinylidene fluorides; Storage capacity; Vinylidene fluoride
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc03556a

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. Liquid crystalline molecule fillers can simultaneously improve the dielectric constant and breakdown strength of a PVDF matrix.