Researchers in the US have created a powerful 3D lithium-ion battery with a tiny footprint that could be used to power tiny scale connected devices and sensors.
Just the size of just one hundred grains of salt, the micro battery has been fashioned by a team of scientists led by Bruce Dunn, a professor at the University of California in Los Angeles (UCLA), using non-traditional techniques.
These techniques include a setup chosen by Dunn's group called a "concentric-tube" design, where an array of evenly spaced anode posts are covered uniformly by a thin layer of a photo-patternable polymer electrolyte and the region between the posts is filled with the cathode material. This is what makes it possible to be scaled to such a tiny size.
The resulting battery achieved an energy density of 5.2 milli-watt-hours per square centimetre
"For small sensors, you need to re-design the battery to be like a skyscraper in New York instead of a ranch house in California," explained Dunn. "That's what a 3D battery does, and we can use semiconductor processing and a conformal electrolyte to make one that is compatible with the demands of small internet-connected devices."
To complete the battery, the research team applied thin layers of electrolyte to the silicon structure and poured in a standard lithium-ion cathode material, using the anode as a mold to ensure that the two halves would fit together correctly.
The resulting battery achieved an energy density of 5.2 milli-watt-hours per square centimetre, among the highest reported for a 3D battery, while occupying a miniscule 0.09 square centimetre footprint and withstanding 100 cycles of charging and discharging.
However, Dunn admitted that this particular 3D battery has not yet reached its full potential, as he hopes that he and his team can boost its energy density with further tuning of battery components and assembly.
"Another challenge with batteries is always the packaging," he added. "You need to seal them up, keep them small, and make sure they function just as well in the real world as in the glovebox."
The research has been published in the scientific journal Joule.
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