Flexible regenerated cellulose films with nanofiber-oriented structure as green dielectrics for dielectric energy storage

With the massive consumption of energy resources and increasingly severe environmental problems, the development of renewable, environmentally friendly, highly efficient energy conversion and storage devices has become a top priority. Here, a microstructure modulation strategy was proposed to fabricate the oriented regenerated cellulose (ORC) dielectric composites with outstanding mechanical and dielectric properties via a combination of dissolution, crosslinking, stretching, and hot-pressing techniques. ORC films with a stretch ratio of 100 % (ORC-100 film) exhibit a significant increase in displacement values (2.96 µC/cm 2 ), breakdown strength (404.04 MV/m), dielectric constant (14.37 at 1 kHz), and energy density (3.42 J/cm 3 at 250 MV/m) as compared to the unstretched regenerated cellulose films. These enhancements are attributed to the anisotropic alignment of cellulose chains and the enhanced crystalline phase of cellulose II, both of which are significantly higher in ORC-100 film. This work offers a feasible and serviceable approach for the development of environmentally friendly cellulose dielectric composites with high performance.