Sprayable battery concept showing each layer vs traditional cell (via Rice University)
Rice University researchers bring us a novel way of creating a lithium-ion rechargeable battery that can be ‘sprayed’ onto almost any surface. Actually the ‘paint’ is sprayed in layers with each effectively representing the traditional make-up of their solidified counterpart. The research team, led by graduate student Neelam Singh, designed the spray-on battery using five key layers that consist of a pair of current collectors, a cathode layer, anode layer and a polymer separator sandwiched in the middle. Each layer is made of a chemical make-up that includes the positive current collector which is refined single walled carbon nano-tubes mixed with black carbon particles diffused in N-methylpyrrolidone (chemical compound used to recover hydrocarbons in petrochemicals).
The cathode layer is a mixture of lithium cobalt oxide, carbon combined with ultra-fine graphite powder in an adhesive solution (unknown solution, most likely a solvent). In comes the polymer separator layer (that divides the anode and cathode layers preventing short circuits) that is made using Kynar Flex resin with PMMA (polymethyl-methacrylate) otherwise known as thermoplastic) and silicon dioxide that is dissipated in a solvent. Next comes the anode layer that is comprised of a lithium-titanium oxide along with ultra-fine graphite powder diffused in a solvent binder. Finally, rounding out the five layers is the anode portion which is comprised of a simple copper paint diluted in ethanol. Combine them in a layered application and presto; instant rechargeable battery! However, you might not want to use your tongue to see if it still has a charge.
Solar and battery tile proof of concept (via Rice University)
The researchers tested the spray-on battery application using a series of surfaces that included ceramic bathroom tiles, flexible polymers (plastic), stainless steel, glass and even a beer stein (talk about getting lit-up). Each surface was coated in each layer using an airbrush, and each was found to be an adequate medium that could hold the chemical layers and maintain a steady charge. One particular experiment the team successfully demonstrated was using 9 ceramic tiles that were individually coated with the spay-on battery and then connected in parallel to each other. The center tile was outfitted with a solar-cell that collected power from a white laboratory light and charged each ‘tile-battery’ which was then able to power a series of LED’s for 6 hours with a stable current of 2.4 volts. The tiles were then tested for reliability by charging/discharging the batteries over a 60 cycle period after which the team found only a slight loss in charge capacity for each battery.
It is the team’s hope that the spray-on batteries could be integrated with paintable solar-cells such as MIT’s bio-photovoltaic cells which are made from plants. Who knows, maybe ‘tag’ artists could use the paintable batteries in their artwork that covers most every train car in America which could then be used to provide a sort of ‘green-power’ fuel for the train itself.