Flexible cellulose/PVDF composite films with improved breakdown strength and energy density for dielectric capacitors

[Display omitted] •Cellulose as biomass material was used for energy-storage dielectrics.•Regenerated cellulose/polyvinylidene fluoride dielectric composite films (RC-PVDF) were prepared by immersion method.•The energy storage density of RC-PVDF reached 8.3 J/cm3 under the electric field of 410 MV/m. .•The introduction of PVDF reduced the water absorption and improved the dielectric properties of the RC-PVDF films. Environment-friendly dielectric materials with high charge–discharge efficiency and energy density are urgently needed in the field of energy storage. Cellulose has the advantages of renewability, non-pollution, wide source, cheapness and so on. However, cellulose is easy to absorb water which causes the decrease of energy storage density in high humidity environment. In this work, polyvinylidene fluoride (PVDF) was used to reduce the hydrophilic of cellulose. Regenerated cellulose (RC)/PVDF dielectric composite films (RC-PVDF) were prepared by immersion method. When the concentration of PVDF solution was 3 wt%, the composite had the best comprehensive performance. The energy storage density of RC-PVDF reached 8.3 J/cm3 under the electric field of 410 MV/m, which was 144 % and 176 % higher than that of RC and PVDF, respectively. This work expands the application of cellulose in humid environment and provides a good choice to develop high-performance biopolymer-based dielectric materials.