Porous battery layer pulls once-a-week EV charging a step closer

Lithium-sulfur batteries are a hugely promising energy storage solution with the type of density that could see smartphones run for five days, and scientists continue to make exciting advances that bring them closer to commercial reality. The latest comes from researchers at Australia's Monash University, who have developed a novel layer component that shapes as a critical piece of the puzzle, offering these devices both a high capacity and long lifetime.

The promise of lithium-sulfur batteries goes beyond their potential to hold more energy on each charge, between two and five times that of today's lithium-ion devices by weight. Lithium-ion batteries rely on metals like cobalt, manganese and nickel, and sourcing these materials carries environmental and humanitarian costs, and supplies are expected to come under strain as the world shifts toward electric transportation.

Sulfur, by contrast, is abundant and cheap, but batteries featuring it have suffered from stability issues stemming from a chemical reaction that takes place as they cycle. During operation, small particles called polysulfides form that cause trouble for the battery's anode and dramatically shorten the device's lifespan.

We've seen some promising solutions to this problem, which include integrating Kevlar fibers to inhibit movement of the polysulfide particles and using a rare chemical phase of sulfur to prevent their formation altogether. The Monash University team has found success in taking yet another approach, focusing on the separator layer that sits between the battery's two electrodes.

The scientists developed a novel version of this important interlayer featuring a unique surface chemistry and uniform network of pores that stifles the movement of the polysulfides. Equally important is the effect this layer has on the transport of lithium ions, promoting their movement to vastly improve the charge and discharge rates of the device.

“A lithium battery interlayer sits in the middle of the battery and keeps the electrodes apart, it helps lithium get from one side of the battery to the other faster," said Professor Matthew Hill, who led the research. "The new interlayer overcomes the slower charge and discharge rates of previous generation lithium-sulfur batteries.”

The design is said to offer excellent protection of the anode and outstanding capacity retention, with the scientists demonstrating its performance across thousands of cycles.

“The interlayer stops polysulfides, a chemical that forms inside this type of battery, from moving across the battery; polysulfides interfere with the anode and shorten the battery life," said lead author, Ehsan Ghasemiestabanati. "It means the battery can be charged and discharged as many as 2,000 times without failing."

The scientists say this type of battery could allow an electric car that only need to be charged once a week, for example, and enable rechargeable batteries that more sustainable than the current crop of lithium-ion batteries.

“These batteries are not dependent on minerals that are going to lack supply as the electrification revolution proceeds, so this is another step towards cheaper, cleaner and higher performing batteries that could be made within Australia,” said Professor Hill.

The research was published in the Journal of Materials Chemistry A.

Source: Monash University