An international team of researchers from the Center for Integrated Nanostructure Physics at the Institute for Basic Science (IBS) and Department of Energy Science at Sungkyunkwan University in South Korea, has devised a new technique for creating a graphene-based MSC (solid-state micro-supercapacitor) that is said to deliver improved electrochemical performance, with a design based on the intricate design of leaves.
The team designed their MSC film structure in compliance with vein-textured leaves in order to take advantage of the natural transport pathways which enable efficient ion diffusion parallel to the graphene planes found within them. To create this efficient shape, the team layered a graphene-hybrid film with copper hydroxide nanowires. After many alternating layers they achieved the desired thickness, and added an acid solution to dissolve the nanowires so that a thin film with nano-impressions was all that remained.
To fabricate the MSCs the film was applied to a plastic layer with thin, ~5μm long parallel gold strips placed on top. Everything not covered by the gold strips was chemically etched away so that only the gold strips on top of a layer of film were left. Gold contact pads perpendicular to the gold strips were added and a conductive gel filled in the remaining spaces and was allowed to solidify. Once peeled from the plastic layer, the finished MSCs resemble clear tape with gold electrical leads on opposite sides.
The team produced excellent results. In addition to its superior energy density, the film was found to be highly flexible and to actually increase capacitance after initial use. The volumetric energy density was 10 times higher than currently available commercial supercapacitors and also far superior to any other recent research. The MSCs are displaying electrical properties about five orders of magnitude higher than similar lithium batteries and are comparable to existing, larger supercapacitors.
The team's MSCs could be, in the future, embedded into an electronic circuit chip as power sources for practical applications such as implantable medical devices, active radio frequency identification tags, micro robots and more. Given graphene's flexibility, the MSCs could be utilized in portable, stretchable and wearable electronic devices.