Flexible dielectric nanocomposite films based on chitin/boron nitride/copper calcium titanate with high energy density

The increasing environmental pollution produced by synthetic polymer stimulates a huge demand for new biodegradable dielectric materials stemming from bioresources. Herein, regenerated chitin (RCH)/boron nitride nanosheets (BNNS)/copper calcium titanate nanofiber (CCTO) composite films were fabricated by simple mixing in aqueous KOH/urea solution. The two-dimensional BNNS possess wide bandgap and excellent intrinsic insulating properties to reduce the dielectric loss, thus exhibiting a greatly enhanced breakdown strength. Simultaneously, CCTO with ultrahigh dielectric constant significantly improved the dielectric constant of these ternary composite films. Accordingly, an extremely high energy storage density of 9.27 J cm−3 was obtained when loaded with 6 wt% BNNS and 5 wt% CCTO. Moreover, a superhigh charge-discharge efficiency of about 80% was well-maintained even when the applied electric field reaches 440 MV m−1. Furthermore, the ternary composite films also possessed much better thermal and mechanical properties.