Moving Toward Invisible Batteries

Wearable transparent electronics are moving from the concept stage to commercialization, thanks in part to the development of flexible, transparent displays. That transition may have just been quickened—and the range of design possibilities broadened—thanks to a study detailing a route to making transparent batteries (ACS Nano 2015, DOI: 10.1021/acsnano.5b03578). Typical procedures for making battery electrodes result in relatively bulky structures that aren’t see-through. Researchers led by Forrest S. Gittleson, Won-Hee Ryu, and André D. Taylor of Yale University have demonstrated that a solution-based electrostatically driven layer-by-layer assembly method can be used to fabricate ultrathin transparent lithium-ion battery electrodes. The team prepared transparent anode and cathode films by spraying solutions of single-walled carbon nanotubes and V₂O₅ nanowires, respectively, onto rotating substrates. They tested the anodes and cathodes separately in lithium-ion reference cells, verifying that the electrodes are electrochemically active and stable. They then coupled the electrodes to make a battery and showed that the test cell could retain its initial charge capacity for more than 100 charge cycles. The battery is still not completely transparent, however, because the electrode separator and current collector are not transparent. The Yale researchers plan to attack those issues next.