Synchronously enhanced breakdown strength and energy storage performance of cellulose acetate sandwich-structured composite films utilizing MXene@PDA nanosheets

Environment-friendly dielectric materials with high energy density and charge-discharge efficiency are urgently required in dielectric capacitors. Here, we prepared the cellulose acetate (CA)-based sandwich-structured composite films by solution casting technique. To reduce the conductivity of MXene and upgrade the compatibility between filler and matrix, MXene was modified by polydopamine (PDA) to obtain MXene@PDA (M@P) hybrid filler, and then it was added into CA matrix to manufacture CA/M@P as the middle layer to significantly improve dielectric constant, while poly(vinylidene fluoride) (PVDF) with excellent insulation property was designed as the outer layers. The results indicate that the strong hydrogen bonding interaction between layers is conducive to the dense internal structure of the composite films, and a prominently strengthened discharged energy density (12.53 J/cm3) and efficiency (72.12 %) at 625 MV/m are reached in composite film containing 1 wt% M@P, with ultrahigh stability during the 106 consecutive charge-discharge measurements. Furthermore, the composite films also exhibit good mechanical properties. This work suggests the practicability of CA in substituting petroleum-based polymers in the dielectric capacitors.