We've seen batteries woven into clothing, minuscule solar panels and power sources that are as flexible and thin as paper, but what about painting on a battery instead?
For scientists from Rice University in Texas, this is exactly what they hoped to achieve. Published in Scientific Reports, Pulickel Ajayan and his colleagues have created a method to 'paint on' batteries -- to any surface.
From bathroom tiles to glass, steel to a beer stein, the technique developed by the team allowed them to spray-paint battery structures instead of relying on the usual 'swiss roll' constraints of traditional battery development.
The batteries the team were able to spray are made of five separate layers -- and together measure no more than 0.5mm in thickness. Going beyond making traditional cylindrical shapes flexible, the team separated the negative and positive halves -- the anode and cathode -- by using the chemical poly-methylmethacrylate.
The trick was this: how to effectively make sure each of the five layers stuck together -- in order to work efficiently -- but remove the limitations of traditional lithium-ion batteries and rigid structures.
Each layer, therefore, first had to be optimized for maximum power output. Pulickel Ajayan and his team engineered each layer to improve their rates of efficiency, using different blends of chemical compounds found in traditional lithium-ion batteries as well as the lesser-explored options that components including carbon nanotubes offer.
What the chemical poly-methylmethacrylate offered was a way to keep each 'stack' in place -- and would also stick to any surface the scientists wished, including curved or uneven surfaces.
The experiment resulted in a working, spray-on battery.
Professor Ajayan said:
"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.
There has been a 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."
"Form factors" -- the shape and size of power output system -- are becoming more challenging as consumer demand for technology including smartphones and electric vehicles increases. These 'spray on' batteries will be of particular interest in the industrial market, as spray-paint technology is already well established. This kind of technique may also have application in the device market, due to its flexible nature and small size.
Image credit: Scientific Reports