Transparent and flexible cellulose dielectric films with high breakdown strength and energy density

Dielectric capacitors with high breakdown strength and energy density are indispensable in pulsed power systems of electric device. Meanwhile the reduction of fossil resources and the improvement of energy requirements promote the development of renewable resources in energy field. Here, regenerated cellulose (RC) films were fabricated via a simple process. The results showed that the dry RC films obtained from suitable cellulose concentration and molecular weight possessed high discharged energy density and efficiency. RC film prepared by dissolution with a cellulose concentration of 3.5%, regeneration with H2SO4 aqueous solution and vacuum drying at 90 ​°C exhibited high efficiency of 84.8% and an ultrahigh discharged energy density of 16.78 ​J/cm3 at breakdown strength of 500 ​MV/m which is around 10 times higher than that of biaxially oriented polypropylene. Therefore, these flexible and transparent cellulose dielectric films are promising in the field of novel high-performance biomass-based film dielectric capacitor.