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Posted on September 05, 2007 by Teresa Henry

A Paper Thin Battery the Size of a Postage Stamp Rensselaer US

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A new energy storage device that is only slightly bigger than the size of a postage stamp has been developed by scientists at Rensselaer Polytechnic Institute.
The nanoengineered battery is lightweight, ultra thin, completely flexible, and likely to meet the demands of the next generation of gadgets, implantable medical equipment, and transportation vehicles.
According to the researchers the device is completely integrated and can be printed like paper and rolled, twisted, folded, or cut into any number of shapes with no loss of mechanical integrity or efficiency. The paper batteries can also be stacked, like a ream of printer paper, to boost the total power output. More than 90 percent of the device is made up of cellulose, the same plant cells used in newsprint, loose leaf, lunch bags, and nearly every other type of paper, making it environmentally safe. The device is also unique in that it can function as both a high-energy battery and a high-power supercapacitor, which are generally separate components in most electrical systems. It can function in temperatures up to 300 degrees Fahrenheit and down to 100 below zero. Another key feature is the capability to use human blood, sweat or urine to help power the battery.
"It's essentially a regular piece of paper, but it's made in a very intelligent way," said paper co-author Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer.
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The paper was infused with aligned carbon nanotubes, which gives the device its black color. The nanotubes act as electrodes and allow the storage devices to conduct electricity. The device, engineered to function as both a lithium-ion battery and a supercapacitor, can provide the long, steady power output comparable to a conventional battery, as well as a supercapacitor's quick burst of high energy.
"We're not putting pieces together - it's a single, integrated device," said Linhardt. "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."
The researchers used ionic liquid, essentially a liquid salt, as the battery's electrolyte. Ionic liquid contains no water, which means there's nothing in the batteries to freeze or evaporate therefore allowing the paper energy storage devices to withstand extreme temperatures.
Along with use in small handheld electronics, the paper batteries' light weight could make them ideal for use in automobiles, aircraft, and even boats. The paper also could be molded into different shapes, such as a car door, which would enable important new engineering innovations.
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Because paper is extremely biocompatible and these new hybrid battery/supercapacitors have potential as power supplies for devices implanted in the body, it was possible for the researchers to print paper batteries without adding any electrolytes - they were able to demonstrate that naturally occurring electrolytes in human sweat, blood, and urine can be used to activate the battery device therefore eliminating harsh chemicals that are typically found in batteries.
The team of researchers has already filed a patent protecting the invention. They are now working on ways to boost the efficiency of the batteries and supercapacitors, and investigating different manufacturing techniques such as printing the paper using a roll-to-roll system similar to how newspapers are printed.
Although the materials required to create the paper batteries are inexpensive, carbon nanotubes are too costly at this stage to mass produce so we are unlikely to see these devices going to market in the near future.
References: Rensselaer Polytechnic Institute
Source top image: Rensselaer Polytechnic Institute
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