Researchers at Rensselaer Polytechnic Institute have developed a battery that's basically a piece of paper impregnated with carbon nanotubes. Robert Linhardt, the senior researcher on the project says that the device isn't built from pieces, but rather it's a single integrated device. Almost 90% of the device is cellulose.
The new battery is lightweight, operates in a wide temperature range, is non-toxic, and multi-function. Not only can it function as a battery--developing steady power--but also provide quick bursts of high energy like a capacitor.
Typically, the batteries use an ionic liquid as the electrolyte, but the batteries have also been shown to work with sweat, blood and even urine as the electrolyte, making the practical and safe for use inside the body.
I couldn't fine information on the density of the device, so I've got no idea whether they'd be viable replacements for batteries in portable electronic devices. But with power management becoming the most challenging aspect of keeping your mobile life on the move, any battery technology advance is welcome news.