Bioinspired, compositionally graded cellulose-based dielectrics with Schottky-engineered interfaces for high-performance and sustainable energy storage.

Abstract

Inspired by the hierarchical structure of the feathers of black swans at the Shaanxi University of Science and Technology (SUST), we developed compositionally graded cellulose-based composite films incorporating BCZT ceramic fillers with varying compositions into a cellulose/P(VDF-HFP) blend film (C8/PH2) for high-performance and sustainable dielectric capacitors. Three configurations-single-layer, down-graded trilayer (C8/PH2-BCZT-dg), and up-graded trilayer (C8/PH2-BCZT-ug)-were fabricated and systematically evaluated. The C8/PH2-BCZT-dg film achieved the highest recoverable energy storage density (W_rec = 38.73 J cm^-3) and efficiency (η = 79.39%), attributed to the stable Schottky emission conduction across its interfaces, as revealed by current-voltage fitting and band-diagram analysis. In contrast, the C8/PH2-BCZT-ug film structure exhibited a conduction-mechanism transition to Ohmic contact, leading to reduced breakdown strength. Finite element simulations confirmed the experimental breakdown trends and highlighted the role of internal potential distribution. The C8/PH2-BCZT-dg film also demonstrated excellent frequency stability (10 Hz-10 kHz), cycling durability (10⁶ cycles), and high-power performance, with rapid energy release (t_0.9 = 41.97 ns) and a discharge energy density of 21.07 J cm^-3 at 5.0 MV cm^-1. Furthermore, combustion testing revealed the superior fire resistance of the film, underscoring its safety for long-term operations. These results establish hydrogen-bond-engineered, compositionally graded cellulose composites as promising eco-friendly alternatives to petroleum-based dielectric materials for advanced energy-storage applications.