A technology breakthrough could increase the range and battery capacity of electric cars by up to five times using a material recycled from bulletproof vests.
Currently lithium-ion (Li-ion) batteries are the industry standard, but lithium-sulfur (Li-S) batteries offer a number of advantages, including increased capacity and the lack of costly cobalt.
While there are currently drawbacks to Li-S batteries, new research from the University of Michigan has shown they may be overcome by adding an electric charge to a membrane made from recycled Kevlar fibres.
Currently Li-S batteries degrade quickly and can't be recharged enough times to make them commercially viable.
There are two main issues that cause this. The first is dendrites, a deposit that forms on the negative battery electrode that can cause short-circuiting and overheating.
The second is caused by lithium polysulfides, which are created when lithium ions react with the positive electrode.
The polysulfides degrade the positive electrode and then flow to the negative electrode and attach to it, causing further degradation of performance.
Dendrites can be blocked by the Kevlar membrane, but the polysulfide issue is more complicated.
Lithium ions need to flow freely between the electrodes for the battery to work, and the polysulfides are similar in size to the ions and therefore blocking on size alone doesn't work.
Researchers overcame this issue by mimicking pores in biological membranes. The addition of the electric charge to the Kevlar nanofibres allow the Lithium ions to pass through while repelling the polysulfides.
"Achieving record levels for multiple parameters for multiple materials properties is what is needed now for car batteries," Nicholas Kotov, the professor who led the research, said.
"It is a bit similar to gymnastics for the Olympics - you have to be perfect all around including the sustainability of their production."
Kotov said the battery design was "nearly perfect". It would handle the temperature extremes car batteries are exposed to as well as full charging in both summer and winter.
While the real-world cycles might not be as close to the theoretical limits, Kotov still expects a battery to last around 1000 cycles, which is considered a ten-year lifespan.
The batteries are also more sustainable than current electric car batteries, thanks to the use of recycled Kevlar from bulletproof vests and sulfur, which is one of the most abundant elements in nature.
