Paper Battery:

A paper battery is a battery engineered to use a spacer formed largely of cellulose (the major constituent of paper).
This technology can also be used in supercapacitors. It incorporates nanoscale structures to act as high surface-area electrodes to improve the conduction of electricity.
Development
The creation of this unique nanocomposite paper drew from a diverse pool of disciplines, requiring expertise in materials science, energy storage, and chemistry. In August 2007, a research team at Rensselaer Polytechnic Institute (led by Drs. Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer; Pulickel M. Ajayan, professor of materials science and engineering; and Omkaram Nalamasu, professor of chemistry with a joint appointment in materials science and engineering) developed the paper battery. Senior research specialist Victor Pushparaj, along with postdoctoral research associates Shaijumon M. Manikoth, Ashavani Kumar, and Saravanababu Murugesan, were co-authors and lead researchers of the project. Other co-authors include research associate Lijie Ci and Rensselaer Nanotechnology Center Laboratory Manager Robert Vajtai.
This cellulose based spacer is compatible with many possible electrolytes. Researchers used ionic liquid, essentially a liquid salt, as the battery’s electrolyte, as well as naturally occurring electrolytes such as human sweat, blood, and urine.
Ionic liquid, which contains no water, would mean that there’s nothing in the batteries to freeze or evaporate, potentially allowing operation in extreme temperatures.
Naturally occurring electrolytes might allow more biocompatible batteries. According to Pushparaj “It’s a way to power a small device such as a pacemaker without introducing any harsh chemicals – such as the kind that are typically found in batteries — into the body.”
Durability
The spacer is an integrated combination of spacer, and electrodes. “It’s essentially a regular piece of paper, but it’s made in a very intelligent way,” said Linhardt, “We’re not putting pieces together — it’s a single, integrated device,” he said. “The components are molecularly attached to each other: the carbon nanotube print is embedded in the paper, and the electrolyte is soaked into the paper. The end result is a device that looks, feels, and weighs the same as paper.”
Uses
The paper-like quality of the battery combined with the structure of the nanotubes embedded within gives them their light weight and low cost, making them attractive for portable electronics, aircraft, automobiles, and toys (such as model aircraft), while their ability to use electrolytes in blood make them potentially useful for medical devices such as pacemakers. The medical uses are particularly attractive because they do not contain any toxic materials and can be biodegradable; a major drawback of chemical cells. However, Professor Sperling cautions that commercial applications may be a long way away, because nanotubes are still relatively expensive to fabricate. Currently they are making devices a few inches in size. In order to be commercially viable, they would like to be able to make them newspaper size; a size which, taken all together, would be powerful enough to power a car.