Australian scientists have found a way to create compact, <a href="http://www.newelectronics.co.uk/electronics-blogs/graphene-supercapacitors-the-ones-to-watch/52167/">graphene based supercapacitors</a> which last as long as conventional batteries.
Supercapacitors are typically made from porous graphite, and can hold about 5W hours per litre. The Monash University team managed an energy density of about 60W hours per litre, about the same as a car battery. While that isn't quite as good as lithium-ion batteries, which typically range between 250 and 750W hours, it's still a big jump over current capacitor technology. To make their supercapacitor, the researchers began by folding sheets of graphene into corrugated shapes. They then put the sheets into an electrolyte solution that kept the layers separated by a few nanometres and provided a path for moving electrons. To test how much charge the sheets could hold, the team applied a current. Because of graphene's unique honeycomb lattice structure and because it was corrugated, the researchers found that there was more surface area for the electrons to gather upon, and thus the supercapacitor could hold more charge in a smaller space. "We have created a macroscopic graphene material that is a step beyond what has been achieved previously," said lead researchers Professor Dan Li. "It is almost at the stage of moving from the lab to commercial development."