For batteries to fit into tinier electronic devices without compromising performance they need “to be built like a skyscraper in New York instead of a ranch house in California,” says Bruce Dunn, a professor of materials science and engineering at the UCLA Samueli School of Engineering. In order to do so, Dunn and his team have developed a powerful 3D lithium ion battery with a footprint equivalent to 100 grains of salt.
The work was supported by the Office of Naval Research, and appears in the journal Joule.
Using a non-traditional semiconductor processing technique, a method Dunn says “the battery world just does not do,” and a conformal electrolyte, he and his team have developed a miniscule battery that is compatible with the demands of even the smallest internet-connected devices.
While the standard two-dimensional battery has an anode and cathode configuration that limits design variations, a 3D anode and cathode setup is able to be snapped together like puzzle pieces in innumerable ways. The design chosen by Dunn’s group is a skyscraper-like “concentric-tube” with evenly spaced anode posts covered uniformly by a thin layer of a photo-patternable polymer electrolyte (to complete the circuit); the region between the posts is filled with the cathode material.
Until now, researchers had been unsuccessful in their attempt to build a functional and powerful 3D battery that is significantly better than ordinary two-dimensional versions. Dunn, the Nippon Sheet Glass Company Professor of Materials Science, and UCLA postdoctoral scholars, Janet Hur and Leland Smith, engineered their version by adopting methods normally used to make semiconductors.
The team carved silicon into a grid of precisely-spaced cylinders for the anode component. To complete the battery, they 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 the two halves fit together perfectly.
The resulting battery achieved an energy density of 5.2 milli-watt-hours per square centimeter, among the highest reported for a 3D battery, while occupying a miniscule 0.09 square centimeter footprint and withstanding 100 cycles of charging and discharging.
Dunn is optimistic that he and his team can ramp up the 3D battery’s potential even further with additional tuning of battery components and assembly.
High Areal Energy Density 3D Lithium-Ion Microbatteries https://www.sciencedirect.com/science/article/pii/S2542435118301399