Miniature supercapacitors based on nanocomposite thin films

Abstract

This paper reports on the development of a miniature supercapacitor for portable applications such as mobile and wearable energy storage. In a primary embodiment, the developed supercapacitor consists of two flexible electrodes fabricated on thin metal base substrates. The electrodes sandwich a solid polymeric separator doped with an appropriate ionic material acting as electrolyte. Different electrode materials including carbon nanotubes (CNTs), silver nano-particulate ink, and nanocomposite of CNTs and polyvinyl alcohol (PVA) were investigated in fabricating the flexible electrodes. Ultrathin and flexible stainless steel sheets of different thicknesses ([email protected], [email protected]) were evaluated as base substrate material. The integrated separator and electrolyte layer was made of polyvinyl alcohol doped with phosphoric acid. The evaluation of different electrode and substrate materials allowed for selection of a combination of materials that yielded optimal supercapacitor performance. Devices with optimal combination of materials exhibited planar capacitance value (>[email protected]/cm^2) significantly higher than the range reported in similar devices. Our investigation of electrode and substrate materials clearly demonstrated that planar capacitance is influenced by factors such as surface area of the electrode and its materials, and the thickness of the base substrate that functions as a current collector.