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 swan in 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, 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 (Wrec=38.73 J/cm³) and efficiency (η=79.39%), attributed to 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 (t0.9~41.97 ns) and a discharge energy density of 21.07 J/cm³ at 5.0 MV/cm. Furthermore, combustion testing revealed superior fire resistance, underscoring its safety for long-term operation. 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.