Thin film battery laboratory prototype image credit: Maria Stromme, Uppsala University; Image of RFID card and reader via katielips via Flickr CC
A new battery made of salt and paper could prove to be an environmentally benign replacement for lithium batteries in things like smart cards, RFID tags, and other low power portable devices. Researchers at Uppsala University in Sweden are testing out a prototype, and while it has a few down sides compared to lithium, it certainly has upsides as well. It sounds like an elementary school science experiment gone pro. Technology Review reports that the new battery is made simply of pressed mats of tangled cellulose fibers acting as the electrodes, and a salt solution acts as the electrolyte - the simple ingredients mean cheap, easy manufacturing and the potential to replace lithium batteries in a range of small portable devices. Now that the researchers have the design down, they're working on making the paper and salt batteries more comparable to lithium in capabilities. According to Technology Review:
Lithium batteries can deliver 4 volts and have energy densities of 200 to 300 milliwatt-hours per gram. In comparison, a single paper battery cell delivers 1 volt and can store up to 25 milliwatt-hours of energy per gram. When providing maximum current, it loses 6 percent of its storage capacity after 100 recharging cycles. However, Stromme says that her team has already run the battery for 1,000 recharging cycles at lower current. She also points out that these are numbers from an initial laboratory prototype.
One thing that is fascinating about the design is not only that it could be more ecologically sound than lithium thanks to its ingredients, but that the cellulose that comprises the paper layers is made from a polluting algae found in seas and lakes. This could not only be a boon for particular water ways should the battery concept make it to manufacturing, but also the composition of the cellulose helps it to charge as much as 100 times faster than lithium. As published in Nano Letters:
"These algae has a special cellulose structure characterised by a very large surface area," says Gustav Nyström, a doctoral student in nanotechnology and the first author of the article. "By coating this structure with a thin layer of conducting polymer, we have succeeded in producing a battery that weighs almost nothing and that has set new charge-time and capacity records for polymer-cellulose-based batteries."
There's still research to do to improve its capabilities, but the scientists are hopeful we could see these thin-film batteries on the market and being used for small devices in as little as three years.
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