High transparent, high strength and high energy storage capability of cellulose triacetate films via incorporating cellulose nanocrystal

Green, renewable, and high-performance dielectric materials is critical for sustainable electronics. Herein, cellulose-based composite dielectric films were synthesized using cellulose nanocrystal (CNC) as a nanofiller and cellulose triacetate (CTA) as the matrix. The results demonstrate that incorporating a small amount of high-modulus CNC (0.3 wt%) reduces structural defects through physical cross-linking and hydrogen bonding between CNC and CTA chains. This interaction acts as a deep charge trap, effectively suppressing carrier migration, while simultaneously increasing the matrix entanglement density and Young's modulus. Consequently, the composite films maintain a optical transmittance of 90%, enhanced thermal stability, and dramatically improved mechanical properties, with tensile strength (50.18 MPa) and tensile modulus (3.62 GPa) increasing by 67.9% and 38.2%, respectively. The breakdown strength is enhanced to 630.68 MV/m, approximately 34.1% higher than that of the pure CTA film (470.32 MV/m). Furthermore, the discharge energy density reaches 4.37 J/cm 3 at 725 MV/m, representing a 1.74-fold increase over that of the pure CTA films, while maintaining an energy efficiency of 70.2% and demonstrating good charge-discharge cycling stability. This study proposes a practical approach toward the design of next-generation dielectric materials that are high-performing, and environmentally sustainable for energy storage.