High-performance dielectric film capacitors based on cellulose/Al2O3 nanosheets/PVDF composites

The design and preparation of novel renewable biomass-based dielectric composites have drawn great attention recently. Here, cellulose was dissolved in NaOH/urea aqueous solution, and Al2O3 nanosheets (AONS) synthe-sized by hydrothermal method were used as fillers. Then the regenerated cellulose (RC)-AONS dielectric com-posite films were prepared by regeneration, washing and drying. The two-dimensional AONS had a better effect on improving the dielectric constant and breakdown strength of the composites, so that the RC-AONS composite film with 5 wt% AONS content reached an energy density of 6.2 J/cm3 at 420 MV/m. Furthermore, in order to improve the dielectric energy storage properties of cellulose films in high humidity environment, the hydro-phobic polyvinylidene fluoride (PVDF) was innovatively introduced to construct RC-AONS-PVDF composite films. The energy storage density of the prepared ternary composite films could reach 8.32 J/cm3 at 400 MV/m, which was 416 % improvement against that of the commercially biaxially oriented polypropylene (2 J/cm3), and could be cycled for >10,000 times under 200 MV/m. Concurrently, the water absorption of the composite film in humidity was effectively reduced. This work broadens the application prospect of biomass-based materials in the field of film dielectric capacitor.

Automated summary

Novel renewable biomass-based cellulose-AONS dielectric composites were prepared by dissolving cellulose in NaOH/urea solution and using hydrothermally synthesized Al2O3 nanosheets as fillers. The addition of two-dimensional AONS significantly improved the dielectric constant and breakdown strength, achieving an energy density of 6.2 J/cm3 for the composite film with 5 wt% AONS content. Moreover, the introduction of hydrophobic PVDF further enhanced the dielectric energy storage properties, with a storage density of 8.32 J/cm3 and more than 10,000 cycles under 200 MV/m.