Superior energy storage capacity of polymer-based bilayer composites by introducing 2D ferroelectric micro-sheets
Zhenhao Fan, Jian Dai, Yuyan Huang, Hang Xie, Yitao Jiao, Wenfeng Yue, Fu Huang, Yuqun Deng, Dawei Wang, Qingfeng Zhang, Yunfei Chang
Abstract
Dielectric polymer capacitors suffer from low discharged energy density and efficiency due to their low breakdown strength, small dielectric constant and large electric hysteresis. Herein, a synergistic enhancement strategy is proposed to significantly increase both breakdown strength and dielectric constant while suppressing hysteresis, through introducing 2-dimensional bismuth layer-structured Na0.5Bi4.5Ti4O15 micro-sheets and designing a unique bilayer structure. Excitingly, an ultra-high discharged energy density of 25.0 J cm−3 and a large efficiency of 81.2% are achieved in Na0.5Bi4.5Ti4O15-poly(vinylidene fluoride-co-hexafluoropropylene)/Na0.5Bi4.5Ti4O15-polyetherimide bilayer composites under a dramatically enhanced breakdown strength of 8283 kV cm−1. Finite element simulations along with experimental test results demonstrate that greatly improved breakdown strength is ascribed to uniform and horizontal alignments of Na0.5Bi4.5Ti4O15 sheets (~1–2 μm) in the matrix and interface effect of adjacent layers with large dielectric differences, which effectively inhibit electrical tree evolution and conduction loss. This work provides a strong foundation for developing high-performance polymer-based energy storage devices. The authors realize high energy storage performance in polymer-based composites by integrating two-dimensional bismuth layer-structured Na0.5Bi4.5Ti4O15 ferroelectric micro-sheets and bilayer structure.