Electric vehicle ranges could increase five-fold thanks to a new, biologically-inspired battery membrane designed by University of Michigan scientists to fix fundamental issues in next-generation lithium-sulphur batteries.
Lithium-sulphur (Li-S) cells can hold five times the charge as the industry standard lithium-ion batteries, but as The Independent reports, they are “wildly impractical” for use in consumer electronics due to an “inherent instability” of the cathodes that causes them to degrade quickly and fail after 10 charging cycles. UMichigan scientists tried to solve this problem by creating a network of nanofibres similar to a cell membrane that blocks degradation.
“Inspired by biological ion channels, we engineered highways for lithium ions where lithium polysulphides cannot pass the tolls,” Ahmet Emre, co-first author of the paper, told UMichigan’s Engineering Research News Center.
Other research teams have made progress extending battery life to several hundred cycles, but those gains were at the expense of other essential parameters, like safety.
“Achieving record levels for multiple parameters for multiple materials properties is what is needed now for car batteries,” said Nicholas Kotov, the chemical sciences and engineering professor who led the research team. “It is a bit similar to gymnastics for the Olympics—you have to be perfect all around, including the sustainability of their production.”
Whereas lithium-ion batteries release or store charge by moving ions between cathodes and anodes, Li-S batteries store and release energy by chemically converting sulphur into a polysulphide and back again. The small sulphur particles in Li-S batteries can drift, and without any way to selectively contain them while allowing the flow of lithium particles, the sulphur attaches to the lithium and degrades the battery, UMichigan explains.
That’s where the membrane created by Kotov’s team comes in. The membrane uses Kevlar—the same material found in bulletproof vests—to selectively control the flow of different particles, in this case by blocking only the sulphur from passing through. With the membrane in place, the Li-S batteries can last the 1,000 or more cycles required for an effective electric vehicle battery.
The new design is “nearly perfect” and could allow Li-S batteries to reach the full potential of their theoretical limits, said Kotov.