Researchers at Rice University in Houston, Texas, have developed a technique that could turn any surface into a lithium-ion battery and, when combined with solar cells, could revolutionise how we generate energy in homes.
Created in the lab of materials scientist Pulickel Ajayan, the rechargeable battery consists of spray-painted layers, each representing different components of the traditional battery.
“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,” said Ajayan.
Converting battery components to paint
Lead author of the research and Rice University graduate student Neelam Singh and her team spent many hours converting the five components, formulating, mixing and testing paints to recreate a positive and negative current collector, a cathode, an anode, and a polymer separator.
“The hardest part was achieving mechanical stability, and the separator played a critical role,” Singh said. “We found that the nanotube and the cathode layers were sticking very well, but if the separator was not mechanically stable, they would peel off the substrate.”
Once they achieved the correct mix for each component, the paints were airbrushed onto nine bathroom tiles. These tiles and other items were then infused with the electrolyte, heat-sealed and charged.
The tiles were connected in parallel and one was topped with a solar cell that converted power from a white laboratory light. When fully charged by both the solar panel and house current, the batteries powered a set of LEDs spelling out ‘RICE’ for six hours, providing a steady current of 2.4 volts.
The researchers reported that the hand-painted batteries were remarkably consistent in their capacity, within plus or minus 10pc of the target, and Singh said they were also put through 60 charge-discharge cycles with only a very small drop in capacity.
Potential when combined with solar power
The battery paint can be applied to any material, such as metal, glass, ceramic or plastic, creating great choice and flexibility for the substrate and shape of batteries.
The painted batteries were easily charged with a small solar cell and Singh foresees the possibility of integrating these with recently reported paintable solar cells to create an energy-harvesting combination that would be hard to beat. “Spray painting is already an industrial process, so it would be very easy to incorporate this into industry,” she said.
The ideal application of this development would be to create a wall of ceramic tiles in a house that are actually batteries, and combine these with solar cells to capture and store energy to use as electricity.
The Rice researchers have filed for a patent on the technique, which they will continue to refine. Singh said they are actively looking for electrolytes that would make it easier to create painted batteries in the open air, and they also envision their batteries as snap-together tiles that can be configured in any number of ways.