Superior energy storage capacity of polymer-based bilayer composites by introducing 2D ferroelectric micro-sheets.

Fan, Zhenhao; Dai, Jian; Huang, Yuyan; Xie, Hang; Jiao, Yitao; Yue, Wenfeng; Huang, Fu; Deng, Yuqun et al. · Nat Commun · 2025

basic_science · Level V

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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 Na<sub>0.5</sub>Bi<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub> micro-sheets and designing a unique bilayer structure. Excitingly, an ultra-high discharged energy density of 25.0 J cm<sup>-3</sup> and a large efficiency of 81.2% are achieved in Na<sub>0.5</sub>Bi<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub>-poly(vinylidene fluoride-co-hexafluoropropylene)/Na<sub>0.5</sub>Bi<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub>-polyetherimide bilayer composites under a dramatically enhanced breakdown strength of 8283 kV cm<sup>-1</sup>. Finite element simulations along with experimental test results demonstrate that greatly improved breakdown strength is ascribed to uniform and horizontal alignments of Na<sub>0.5</sub>Bi<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub> 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.