Batteries of the future set to be cheaper and better — just by adding sugar – ABC News

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By technology reporter James Purtill
Australian researchers say they've opened the path to a new generation of batteries that could allow an electric vehicle to drive from Melbourne to Sydney on a single charge.
And the crucial ingredient was a spoonful of sugar.
Electric vehicles (EVs), mobile phones and other consumer electronics mostly use lithium-ion batteries that were commercialised in the 1990s.
They're made using toxic and exotic materials such as cobalt, nickel and manganese that are in increasingly short supply around the world.
Fortunately, there is an alternative; lithium-sulfur batteries use cheaper, more abundant materials and are able to store two to five times more energy per kilogram than lithium-ion ones.
But there's a hitch — they degrade rapidly through the process of being recharged.
Now a team from Monash University say they've found a way of making lithium-sulfur batteries that are robust enough to be recharged 1,000 times.
Supplied: Monash Energy Institute
Their research was published this week in the journal Nature Communications.
In addition to this, they say the batteries cost significantly less to make than lithium-ion equivalents.
Here's how they work.
In a lithium-sulfur battery, energy is stored when positively charged lithium ions are absorbed by an electrode made of sulfur particles.
The electrode swells up to almost double its size when it is fully charged, then shrinks as it's discharged.
The expansion and contraction caused by the cycle of charging and recharging weakens and distorts the electrode; this is the first reason why the battery's performance decays very quickly.
The second reason is what's known as the "polysulfide shuttle" problem.
Supplied: ResearchGate, Marco Agostini
When lithium ions are absorbed by the sulfur electrode, they react to form lithium-containing sulfur compounds known as polysulfides.
This has two effects: the removal of sulfur gradually degrades the cathode (the positive terminal when the battery is discharging), and the polysulfides then form what the Monash researchers called a "mossy growth" on the anode (which is the negative terminal when discharging).
This insulates the anode and decays the battery's performance.
While most lithium-ion batteries have a rated lifetime of somewhere between 500 and 1,500 charge cycles, lithium-sulfur ones have been limited to about 50.
Last year, the Monash team demonstrated a partial solution to the cathode issue.
By creating a springy matrix of carbon and sulfur compounds that was better able to expand and contract without distortion or cracking, they boosted the durability of the batteries to 200 charge cycles.
Supplied
But this still left the polysulfide shuttle problem; the solution here was inspired by an unlikely source, according to Mainak Majumder, who was a co-author on the research.
Professor Majumder's PhD student, Yingyi Huang, found a geochemistry paper published in the late 1980s, describing how sugar can help soil retain sulfur compounds.
"She found this in the paper and said, 'Hey Mainak, let's try this'. We tried it and lo and behold it worked and Yingyi was very excited about that." 
Incorporating a "glucose-based additive" into the springy cathode matrix "stabilised" the sulfur and prevented it from dispersing and coating the lithium electrode, he said.
It also improved the web-like structure of the cathode, "opening up" the matrix so there was more space for lithium ions to interact with the sulfur.
Supplied: Monash Energy Institute
This increased the battery's durability to 1,000 cycles; a five-fold improvement.
Professor Majumder said other additives may increase that figure.
"What we have learned from the exercise is we can now find other materials that are similar to sugar and can stabilise the sulfur even better,"  he said.
As a result of this discovery, Professor Majumder believes the Monash team can develop a prototype battery able to store two to three times more energy than a lithium-ion battery of the same size.
"I think what we're hoping to do next year is make a large number or different types of prototypes and convince the world we can get to thousands of cycles at 500Wh/kg," he said.
"There are technical challenges, but I think those challenges will not be difficult to overcome."
An EV with one of these batteries could travel between Sydney and Melbourne (about 900km) on a single charge.
Because these batteries use cheap and abundant sulfur, they would also be cheaper to make than lithium-ion ones, which require cobalt and nickel.
Take a look at what researchers think it's actually worth getting excited about.
The race to mine these expensive elements has become a source of international conflict, as well as environmental degradation.
"We have all the ingredients to make this battery in Australia," Professor Majumder said.
Enserv Australia, a small energy research company, said it planned to make the first lithium-sulfur batteries in Australia within about five years.
"We would be looking to use the technology to enter the growing market for electric vehicles and electronic devices," the company's managing director, Mark Gustowski, said.
The discovery was "very important", said Alexey Glushenkov, an associate professor and expert on battery materials at the Australian National University's Battery Storage and Grid Integration Program.
"It will not enable a battery for common use straight away, but it's definitely a step ahead," said Dr Glushenkov, who was not involved in the research.
"I do believe there will be a prototype that will be usable in five to 10 years."
But, he said, while lithium-sulfur batteries were a "leading contender" for replacing lithium-ion ones, they needed to be made more robust and stable, despite the improvements made by the Monash team.
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Some recently developed lithium-ion batteries can be charged and discharged at least 10,000 times.
Professor Majumder argued that cheaper lithium-sulfur batteries might be able to compete with lithium-ion ones, even if they had to be replaced more often.
"The price of EVs is coming from the cost of the battery," he said.
"If you could get an EV at the price of a Toyota Corolla, I'm sure a lot of people would be buying it."
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