News ID: 171125
Published: 0123 GMT October 29, 2016

Gut instinct drives battery boost

Gut instinct drives battery boost

Scientists have designed a new prototype battery that mimics the structure of the human intestines.

It's a type of battery called lithium-sulfur, which — in theory — could have five times the energy density of the lithium-ion forms in wide use today, according to bbc.com.

But the prototype developed by a UK-Chinese team overcomes a key hurdle to their commercial development by taking inspiration from the gut. Details appear in the journal Advanced Functional Materials.

Scientists are tackling the challenge of improving battery technology using a variety of different approaches; this is one of them.

One of the problems hindering the commercial development of lithium-sulfur-based devices has been the degradation of the batteries caused by the loss of active materials within.

To overcome this problem, the researchers developed a lightweight layer with nano-scale structure which resembles the villi — finger — like protrusions which line the small intestine.

In humans, villi are used to absorb the products of digestion and increase the surface area across which this process can take place.

In the new lithium-sulfur battery, a layer of material with a villi-like structure, made from tiny zinc oxide wires, is placed on the surface of one of the battery's electrodes.

This can trap fragments of the active material when they break off, keeping them accessible for ongoing reactions and allowing the material to be reused.

"It's a tiny thing, this layer, but it's important," said study coauthor Dr. Paul Coxon from the University of Cambridge's department of materials science and metallurgy.

"This gets us a long way through the bottleneck which is preventing the development of better batteries."

The researchers say that, if hurdles to commercial development can be overcome, lithium-sulfur batteries could have five times the energy density of the lithium-ion batteries used in smartphones and other electronics.

But as lithium-sulfur batteries discharge, sulfur molecules transform into chain-like structures known as poly-sulfides.

As the devices undergo several charge-discharge cycles, bits of the poly-sulfide go into the battery's electrolyte (the electrically-conducting solution), so that over time the battery loses active material.

Lead author Teng Zhao, a PhD student from Cambridge, said, "This is the first time a chemically functional layer with a well-organized nano-architecture has been proposed to trap and reuse the dissolved active materials during battery charging and discharging.

"By taking our inspiration from the natural world, we were able to come up with a solution that we hope will accelerate the development of next-generation batteries."

The device is currently a proof of principle; commercially-available lithium-sulfur batteries are still some years away.

Additionally, while the number of times the battery can be charged and discharged has been improved, it is still not able to go through as many charge cycles as a lithium-ion battery.

But the researchers point out that, given a lithium-sulfur battery does not need to be charged as often as a lithium-ion battery, it may be the case that the increase in energy density cancels out the lower total number of charge-discharge cycles.

   
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