High energy storage performance of triple-layered nanocomposites with aligned conductive nanofillers over a broad electric field range

Simultaneously achieving high energy density (U_e) and charge-discharge efficiency (η) of dielectric materials at the relatively low operating electric field remains a persistent challenge to their practical applications. Herein, a P(VDF-HFP)-based triple-layer film by introducing the core-shell Al₂O₃@CNT in the middle layer and 0.05 wt.% boron nitride nanosheets (BNNSs) in the outer layers is designed. The experimental and simulated results confirm that the strategy of in-plane aligned Al₂O₃@CNTs can rapidly improve the dielectric constant of nanocomposites and reduce the probability of forming conductive pathways between neighboring layers. Meanwhile, the outer layers with BNNSs inclusions block the propagation of electric branches and suppress the leakage current, addressing the critical problem of the sacrificed breakdown strength and efficiency in the nanocomposites. Consequently, the as-prepared nanocomposite simultaneously exhibits great U_e and η under various ranges of electric fields. For instance, our results reported its U_e of 20.4 J cm⁻³ with η of 77 % at 520 V μm⁻¹ and U_e of 27.0 J cm⁻³ with η of 76 % at 619 V μm⁻¹. Importantly, the operating electric field for these high U_e and η is significantly reduced 20–50 % than the reported ferroelectric nanocomposites. Moreover, benefitting from the ultra-low fraction (<1.0 wt.%) of nanofillers, the nanocomposites demonstrate excellent stability in energy storage performance after 10,000 bending fatigue cycles. This work offers an effective approach to explore scalable and high-performance nanocomposites used as viable electrostatic capacitors.