Clay key for better supercapacitors

A composite of clay and an electrolyte serves as both electrolyte and a separator in a supercapacitor. Photo credit: Ajayan Group/Rice University

A composite of clay and electrolyte serves as both electrolyte and separator in a supercapacitor. Photo credit: Ajayan Group/Rice University

Supercapacitors have been in the news a lot recently, with researchers and investors alike hoping they can combine the rapid charging and high energy densities of conventional capacitor devices with the slow release of energy associated with batteries.
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Onion rings to feed Li-ion?

Hexagonal graphene “onion rings” grown at Rice University.

Hexagonal graphene “onion rings” grown at Rice University. Photo: Tour Group/Rice University

Researchers at Rice University have discovered a potentially new graphene variant that could be applied to lithium-ion (Li-ion) batteries. Concentric hexagons of graphene grown in a furnace at the university represent the first time anyone has synthesised graphene nanoribbons on metal from the bottom up, atom by atom.
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Nanotechnologists produce micro-supercapacitor

Researchers at Rice University in the US have made a new hybrid micro-supercapacitor from graphene and carbon nanotube ‘carpets’, reports nantechweb.org. These structures have electrochemical properties that could be just the thing for running portable electronics and renewable power applications, longer. With an energy density of 2.42 mWh/cm3 in an ionic liquid, the device carries two times the energy of conventional aluminum electrolytic capacitors of the same volume.

Why energy storage is really superficial

If you want to improve the performance of batteries and capacitors, one sure-fire way is to increase charge density. And the way to do this is to up-scale the surface area of your electrodes. Various configurations of carbon, both alone and in combination with other elements, can provide that increase, which is why we have reported on everything from nanoflowers to a carbon nanofoam.

The latest news in the battle for increased surface area comes from Rice University, where scientists have seamlessly combined carbon nanotubes a few atoms wide and 120 microns long onto one-atom thick graphene sheets, reports Science Daily. That means that if the nanotubes were the same width as an average house, they would rise up from the graphene ‘ground’ like mega-skyscrapers… into space.

As you can imagine, that’s a lot of surface area: 2,000 square metres per gramme of material, in fact. But what about practical applications? Researchers at Rice say their tests indicate the material already performs as well as the best carbon super-capacitors.