Flexible cyanoethyl cellulose-based nanocomposites with superior energy storage capability

Abstract

Flexible dielectric materials for electrostatic energy storage have shown irreplaceable advantages to apply in power modules and modern electronics. However, traditional polymer-based composite films suffer from energy storage performances, for example, discharged energy density (U_d) < 15 J cm⁻³ and efficiency (η) < 70%. Herein, new polymer-based composite films, which combine two-dimensional BN nanosheets (2D BNNs) and cyanoethyl cellulose (CRC), are designed and prepared utilizing the solution casting method. The combination of phase-field simulations and the experimental results reveals that the band-gap in 2D BNNs acts as a charge-blocking barrier to hinder charge carrier movement and conductive path formation, resulting in significantly improved breakdown strength. Accordingly, the optimized composite films exhibit a large U_d of 23.5 J cm⁻³ along with a high η value of 83.6% at 680 MV m⁻¹, which is the highest U_d reported so far using cellulose-based composite films. The current study provides a new paradigm for the development of high-performance and green natural polymer-based dielectric capacitors.