Spray-on batteries could change device design

We’ve done a great job of producing batteries in ever decreasing sizes, but one limitation is that they still remain fixed shapes: largely cylinders with the occasional disc or rectangular block. That in turn places restrictions on the design of battery-powered devices. Now a new technique could mean flat or even curved batteries that fit a wider ranger of housings.

The system, developed at Rice University in Houston, allows a battery to be applied to a surface in the same way as spray-paint.

The logic behind the system is that a battery has five active parts: the anode and cathode (negative and positive), a separating material, and two separate current collectors. Standard cylinder batteries have these materials as five layers that are then rolled up together.

The new system works by reproducing the contents of each parts into a sprayable liquid. These are overlaid, producing a battery just half a millimer thick. The key is that the separating material includes Poly(methyl methacrylate), also known as acrylic glass. As the name suggests, it’s a transparent material that is lighter than glass and shatter-resistant.

Using this material means that the layers of the battery stay together, while the battery can fix itself to a wide range of surface. In testing this worked on ceramic, glass and steel. The battery also worked when sprayed onto the curved surface of a beer stein.

To check the battery provided power as well as staying in place, researchers sprayed enough “paint” to cover nine bathroom tiles. These were then able to provide the 2.4 volts needed to power a set of LEDs for six hours.

At the moment the main drawback is that producing the liquids that make up the battery can only be done in a dry and oxygen-free environment. The list of components would therefore have to be tweaked to allow it to be mass-produced at an affordable price.

Another potential use of the technology would be to adapt it to solar-powered batteries, meaning surfaces could be sprayed and used to capture energy without the need to attach dedicated panels.

(Image credit: Scientific Reports via nature.com)