Researchers from Rice University have cooked up a rather interesting and promising battery technology capable of turning any surface into a lithium-ion battery. The technology consists of five spray-painted layers that make up all the components of a traditional battery, including two current collectors, a cathode, an anode, and a polymer separator in the middle. All that remains is a power source, and as the researchers demonstrated, spray-paintable batteries can be combined with solar cells.
"This means traditional packaging for batteries has given way to a much more flexible approach that allows all kinds of new design and integration possibilities for storage devices," said scientist Pullickel Ajayan, Rice’s Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry. "There has been lot of interest in recent times in creating power sources with an improved form factor, and this is a big step forward in that direction."
The researchers describe each layer as an "optimized stew." It starts with a current collector as the base, which is a mixture of purified single-wall carbon nanotubes with carbon black particles dispersed in N-methylpyrrolidone. A second cathode layer is made with lithium cobalt oxide, carbon, and ultrafine graphite (UFG) powder in a binder solution. The third layer is a polymer separator paint of Kynar Flex resin, PMMA, and silicon dioxide dispersed in a solvent mixture. On top of that sits an anode made of a mixture of lithium titanium oxide and UFG in a binder, and the last layer consists of a negative collector constructed with conductive copper paint diluted with ethanol.
To demonstrate the technology, the researchers applied spray-paintable batteries to a number of surfaces, including a series of bathroom tiles connected in parallel. It was topped off with a solar cell to convert white laboratory light into power, which the spray-paintable batteries used to illuminate a set of LEDs that spelled "RICE" for six hours with a steady stream of 2.4V.
An extensive examination of the science behind it all appears in Nature's online, open-access journal Scientific Reports.