A new research paper from the group of Associate Professor Jiandi Wan in the Department of Chemical Engineering at the University of California, Davis, published in Science Advances, Proposes a potential solution to dendritic growth in rechargeable lithium metal batteries. In the paper, Wan’s team demonstrated that an influx of ions near the cathode could increase the safety and life of these next-generation rechargeable batteries.
Lithium metal batteries use lithium metal as the anode. These batteries have a high charge density and will likely double the power of conventional lithium-ion batteries, but safety is a major concern. When charged, some of the ions are reduced to the lithium metal at the cathode surface and are irregularly shaped like tree-like structures known as dendrites, which can eventually cause a short circuit or even an explosion.
The theory is that dendrite growth results from competition between mass transfer and the rate of lithium ions reduction near the cathode surface. When the rate of ion reduction is much faster than the mass transfer, it creates an electronically neutral gap called the space-charged layer near the cathode which does not contain ions. The instability of this layer is thought to cause dendrite growth, so reducing or removing it may reduce bifurcation growth and thus extend battery life.
Dendrite growth decreased 99 percent
Wan’s idea was to flow ions through the cathode in a microfluidic channel to recover the charge and make up for this gap. In the paper, the team identified proof-of-concept tests and found that this influx of ions can reduce dendrite growth by up to 99 percent.
For Wan, the study is exciting because it shows the effectiveness of applying microfluidics to battery-related problems and paves the way for future research in this area.
“Through this basic study and microfluidic approaches, we were able to quantitatively understand the effect of flow on dendrite growth,” he said. “Not many groups have studied this yet.”
Although it is unlikely to incorporate microfluidics directly into real batteries, the Wan group is looking for alternative methods to apply basic principles from this study and introduce local flows near the cathode surface to offset cations and eliminate the space-charging layer.
“We are very excited to explore new applications for our study,” he said. “We are already working on designing the cathode surface to introduce convection flows.”