However, researchers from Rensselaer Polytechnic Institute and MIT have developed a new material that eliminates the need for a multilayer battery. They grew carbon nanotubes on a silicon substrate and impregnated the gaps between the tubes with cellulose—that's right, plain old paper. The cellulose also covered the ends of the nanotubes, but once it had dried, the paper material could be peeled off of the silicon substrate, leaving one end of the carbon nanotubes exposed to form an electrode.More info at ARS Technica>/A>.
By putting two sheets of paper together with the cellulose side facing inwards (and a drop of electrolyte on the paper), a supercapacitor is formed. These supercapacitors retain the flexibility of normal paper, but they have a rating that is comparable to that of standard commercial hardware—a 100g sheet could replace a 1300mAh battery. Because the medium is flexible, the researchers say you could shape batteries of all sizes for very specific use.
It doesn't stop there, however. By putting a drop of electrolyte on a single sheet and then putting a metal foil consisting of lithium and aluminum on each side, a lithium ion battery is formed. This paper device had a respectable 110mAh/g capacity, and the researchers indicate that small prototypes could already power small mechanical devices like fans. These batteries and supercapacitors are quite stable and have been shown to operate over a wide range of temperatures, with the research showing that they can operate between -78–150°.
Scientists present paper-thin, biodegradable nanobattery
Posted on Thursday, Aug 16 2007 @ 04:00 CEST by Thomas De Maesschalck