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

[Display omitted] •Chitin was used as a green biomass matrix to produce dielectric film capacitors.•The CCTO nanofibers were prepared byelectrospinning.•Chitin/BNNS/CCTO composites were fabricated through dissolution/regeneration process.•The dielectric properties of composites were improved by the incorporation of BNNS and CCTO.•The composites also showed great mechanical properties and thermal stability. 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.