Lithium-sulfur batteries could replace lithium-ion ones in theory at least, because they have five times the storage potential. However to date their capacity, charging rate, resilience and safety have quenched this hope. But this could change thanks to ongoing work at University of Michigan, resulting in a kevlar fiber membrane for lithium-sulfur batteries.
Challenges Facing Lithium-Sulfur Batteries
Lithium-sulfur batteries have until now only been able to tolerate a disappointingly few charging-recharging cycles. This is because the materials are inherently unstable. They soon form dendrites that could puncture the membrane barrier, and short-circuit the battery.
Moreover, chemical reactions inside these batteries can cause cathodes to expand 78% during each charging cycle. These two disadvantages can lead to battery fires – hardly a pleasant experience inside electric vehicles.
But scientists at University of Michigan say they have a solution that increases the recycling rate from tens to hundreds. Moreover, this also meets other challenges including battery cost, and the risk of dendrites causing fires.
A Kevlar Fiber Membrane for Lithium-Sulfur Batteries
The team under guidance of engineer Nicholas Kotov has developed a kevlar fiber membrane for lithium-sulfur batteries. Its pores are more than large enough for lithium ions to flow through, but they are too small for dendrites to pass.
The average battery membrane’s pores are a few hundred nanometers diameter according to FreeThink.Com. However, the kevlar holes are a mere fifteen to twenty by comparison. Or 0.02% the thickness of a sheet of paper if we could imagine that.
Eliminating the dendrite problem theoretically expands the recycling life to over 1,000, or ten years for the average electric vehicle. ‘The special feature of this material is we can make it very thin,’ another engineer explains.
‘So we can get more energy into the same battery cell size, or we can shrink the cell size. We’ve seen a lot of interest from people looking to make thinner products.’ Thirty businesses have already requested samples of the kevlar membrane. The report is pending in the journal Nature Communications.
Related Posts
Root Cause of Lithium Dendrites & Whiskers
Comparing Lithium-Sulfur & Lithium-ion Cells
