Seawater Could Drive Tomorrow's Batteries in Place of Scarce Lithium, Claim Researchers

Researchers from the Universities of Southern Denmark and Copenhagen and the Massachusetts Institute of Technology (MIT) have made strides towards replacing lithium in batteries with something rather more readily available: sodium from seawater.

"An obvious advantage is that sodium is a very readily available resource, which is found in very large quantities in seawater," explains co-author Dorthe Bomholdt Ravnsbæk of the research's potential impact. "Lithium, on the other hand, is a limited resource that is mined only in a few places in the world." Other advantages of the Na-ion battery technology is that it doesn't require cobalt, a mineral mind in its majority in the Democratic Republic of Congo under often morally questionable conditions.

The biggest hurdle to Na-ion batteries have been their relatively low capacity to store energy, something the researchers have found a way around through the addition of manganese to the iron and phosphorus that makes up the electrode — causing a dramatic change in the atomic-level transformations that take place during the charge-discharge cycle. "Similar effects have been seen in Li-ion batteries, but it is very surprising that the effect is retained in a Na-ion battery," Ravnsbæk explains, "since the interaction between the electrode and Na-ions is very different from that of Li-ions."

The team's design can be constructed in factories currently tooled towards Li-ion batteries, the team claim, but there are several hurdles between the research paper and commercialisation — in particular issues with creating the sort of compact batteries that would go into smartphones, watches, and other consumer devices. "The Na-ion battery is still under development," Ravnsbæk admits, "and researchers are working on increasing its service life, lowering its charging time and making batteries that can deliver many watts."

The team's paper has been published in the journal ACS Applied Energy Materials.