Synchronously improved energy storage density and water resistance of cellulose/MXene composite film via glutaraldehyde-assisted crosslinking

Utilizing biomass to create eco-friendly dielectric materials satisfies the criteria for sustainable development in terms of both environmental protection and economic growth, but the relatively low energy storage density is far below the application requirements. Here, regenerated cellulose/MXene (RC/M) composite films were manufactured, and a glutaraldehyde (GA)-assisted crosslinking was proposed to further tailor the microstructure and performances of the RC/M composite films. The results suggested that likened to the original RC/M composite films without crosslinking, the crosslinked composite films (CRC/M) exhibited more integrated structure and fewer defects, apparently reduced dielectric loss and largely enhanced breakdown strength. Consequently, at 288.61 MV/m with MXene concentration of 1 wt%, the energy storage density achieved to 2.41 J/cm3, which was around 6.34 and 1.13 times those of the neat RC film (0.38 J/cm3) and pure CRC film (2.12 J/cm3), respectively. Crosslinking reaction consumed the polar groups of MXene and cellulose matrix, leading to the great reduction of hydrophilicity of the composites, which reduced the water adsorption ability, facilitating the improvement of MXene stability. The effects of storage mode and time on evolution of dielectric performances were also studied. The good comprehensive properties endow the CRC/M composite films with potential applications in next generation dielectric capacitors.