CULPRIT OF BATTERY DETERIORATION
Just like us, batteries — the building blocks of modern life that power our trusted smartphones, laptops and electric cars — are susceptible to aging. Our wallets know a bit too well how expensive this aging can be. Replacing the battery of an iPhone, for example, can cost about $70, if not more.
A trio of a UCSB professor and graduate students, however, have made a discovery that could boost the lifespan of the batteries in our households.
The majority of battery deterioration could be attributed to manganese fleeing the battery. This escape, according to Chris G. Van de Walle — the professor of the researcher trio — is puzzling because “it is very difficult for manganese to leave. In principal, the electrode should be stable.”
In reality however, the manganese atoms, over time, tend to leave the battery, whether they are lithium-ion or sodium-ion.
And though “for Li-ion batteries, the degradation processes of lithium manganates have been widely studied,” writes the trio in their Chemistry of Materials journal paper, “attempts to explain degradation in Na-ion batteries using similar mechanisms have not been successful.”
With not much previous research to shed light on why sodium-ion batteries’ manganese atoms flee, Dr. Van de Walle and his co-researchers Zhen Zhu — now a Google software Engineer — and Hartwin Peelaers — now a University of Kansas professor — wondered what could be enabling the escape. Could it be, pondered the trio, hydrogen?
Hydrogen, with its lone nucleon and even lonelier electron, stands tall on the periodic table as its first element. It is often referred to as the basis of life, because without hydrogen there would be no water on Earth. As such, this basis of life can be found pretty easily, and Dr. Van de Walle and his team decided to see if hydrogen enables the manganese in sodium-ion batteries to run away.
To find the answer, the trio secured a grant from the U.S. Department of Energy and went to work at Berkeley’s National Energy Research Scientific Computing Center, where a troop of supercomputers is stationed. These supercomputers allowed the researchers to run simulations in which sodium-ion batteries were exposed to hydrogen. The simulations conducted used calculations that have been “extensively tested on problems where experimentally the answer is well known,” said Dr. Van de Walle.
These calculations showed that hydrogen does indeed pave the way for manganese atoms to flee, leaving the sodium-ion battery to lose its capacity.
How could this be prevented? By making sure batteries are shut securely.
“Batteries are not terribly well-sealed,” said Dr. Van de Walle.
If batteries were better sealed to shut out the hydrogen, the process of manganese atoms making a run for it could be prolonged, if not prevented. Battery manufacturers, however, may not want to take on the cost of shutting batteries tighter to prevent hydrogen from seeping in. And, of course, with deterioration comes replacement, which would bring more revenue.
Improving the performance of sodium-ion batteries, though, may bring several benefits to a country, if not the world.
“Lithium is expensive and relatively scarce,” said Dr. Van de Walle, “it’s only produced by certain countries in the world.”
The top lithium-producing countries are Argentina, Australia, Bolivia, Chile and China. And whenever highly demanded commodities can only be found in certain areas of the planet, the threat of a cartel looms, making people living outside the resourceful regions twitch with fear of an embargo. Developing sodium-ion technology could free battery users from that fear because sodium is far more abundant than lithium.
Lithium mining has also received criticism for its trail of pollution. Ganzizhou Rongda Lithium Co Ltd. — the subsidiary of Chinese lithium company Youngy Co Ltd. — for example, has received backlash for leaking toxic chemicals into the Liqi River in the southwestern Chinese province of Sichuan. Acquiring sodium, in comparison, would be less strenuous due to sodium’s abundant nature.
And because of this abundance, said Dr. Van de Walle, sodium-ion batteries would definitely be cheaper.
There’s still a long way to go, though, before salt-powered batteries could compete commercially with lithium-ion ones. More research and development, however, may turn the tide.