Solid State Electrolytes Could Solve Li-ion Safety Worries

Researchers working independently at universities on the opposite side of the globe have made progress in making Li-ion batteries safer and more efficient by replacing liquid electrolytes with solids. As the launch of Samsung’s Galaxy Note 5 showed, although we rely heavily on Li-ion batteries, they are by no means as safe as we need them to be. At the same time, consumers are demanding applications that strain the capabilities of today’s battery technologies, for example 4K recording and playback on mobile devices. 

Now, researchers at Virginia Commonwealth University and Shizuoka University in Japan have made strides at driving battery technology forwards. The Virginia Commonwealth University researchers published the findings from their work in the Proceedings of the National Academy of Sciences this month.

The electrolytes in Li-ion batteries carry the charge between the two electrodes. Liquid electrolyte can be a hazard due to a risk of fire, or toxicity, but it provides a superior medium for conduction between the two poles. The research by Puru Jena, Ph.D., a professor at Virginia Commonwealth University and Hong Fang, a postdoctoral fellow at the same university showed that solid-state electrolytes can be as conductive as liquid ones without the inherent risks from the liquid electrolytes, which could lead to safer batteries. 

Positive lithium ions can move freely between electrodes when in a liquid, but traditionally can’t move as well in a solid electrolyte, which lowers the overall conductivity. The Virginia researchers modelled a solid-state electrolyte which removes a single negative ion from the electrolyte. That ion is replaces by negative cluster ions. The original positive electrolyte is comprised of three Li atoms and an oxygen atom. These positive atoms are mixed with a negative chloride atom. The researchers modelled a scenario that removed the chloride atom and replaced it with a cluster containing one boron and four fluorine atoms to make a solid-state electrolyte with similar traits to the liquid one. Other models showed that different ion clusters have the potential to increase the conductivity of the electrolyte. Jena and Fang are now looking for collaboration to test their theoretical model in a real laboratory.

At the same time in Japan, researchers from Shizuoka University have also looked at new solids-based electrolytes. The Shizuoka researchers had their recent work published in the journal Science and Technology of Advanced Materials. The research concentrated on adding an organic compound to lithium salt, which led to molecules that self-assembled to form channels that allowed the lithium ions to flow freely. The new electrolyte was less flammable than traditional liquid electrolytes and had a similar conductivity to polymer electrolytes.

PSD