Sustainable high-performance dielectrics from cyanoethylated ramie cellulose for energy storage

The environmental concerns associated with petroleum-based dielectric polymers have driven interest in sustainable biomass alternatives. Herein, we report a facile chemical conversion of ramie cellulose into high-performance cyanoethyl cellulose (CEC) dielectric films via a dual-reaction pathways of Michael addition and S N 1 nucleophilic substitution. Compared to recent CEC studies (e.g., Yu et al., 2024), this work achieves a critical advancement by simultaneously realizing a substantially enhanced dielectric constant and robust mechanical integrity. The optimized CEC film exhibits an outstanding dielectric constant (ε r = 18.7 ± 0.3 at 1 kHz) and a high breakdown strength (E b = 430 MV·m⁻¹), leading to an impressive discharge energy density (U d = 3.5 ± 0.5 J·cm −3 ) with 81% efficiency at 250 MV·m⁻¹ —among the highest reported for cellulose-based dielectrics. Additionally, the film maintains consistently low dielectric loss (< 0.02) and excellent thermal stability across varying temperatures and frequencies. By transforming agricultural biomass into a high-performance functional material, this work offers an eco-friendly pathway toward sustainable dielectric polymers, contributing to both waste valorization and carbon neutrality goals.