Could the Future Be Powered by Salt? This Researcher Thinks It's Possible

Sodium batteries could make a come-back. 

by James Dennin

If battery innovation were a cocktail party, lithium ion would be the one sucking up all the oxygen in the room, telling too many jokes and barely letting anyone get a word in edge wise. Naturally, Tesla plays no small part in this, which uses lithium ion batteries in its cars and on projects like the Hornsdale Power Reserve, an effort to construct the largest lithium ion battery in the world in Western Australia.

But the battery variety’s dominance stretches back much farther, to the early 1990s when Sony first commercialized them and began putting them in portable devices. Since then, companies have poured time, money, and research into making lithium ion batteries better, and they now power everything from smartphone to cars.

But these lithium ion batteries aren’t perfect, either, explains Shirley Meng, a nano-engineering professor at the University of California San Diego. They’re expensive, for one, and they require the use of cobalt, which can sometimes be a conflict mineral. Together with her colleagues, Meng recently started looking into the question of whether our infatuation with lithium ion might be overshadowing other more promising areas of battery research, for example, batteries made from sodium. 

“Early in the 1960s a lot of researchers worked on sodium ion batteries,” Meng tells Inverse. “The reason it did not take off, is that lithium ion has a voltage that is very high and it’s very good for transistors, so smart phones. So sodium’s voltage is… inherently lower than that of lithium. So there’s a 10 year period of no research into sodium batteries.”

Because of their voltage and portability, lithium ion batteries became the defacto battery, possibly drowning out other promising areas of research. 

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Why Make Batteries Out of Salt?

The main reason why the prospect of sodium ion batteries is so exciting? Salt is hyper-abundant, meaning that sodium ion batteries would, in theory, be quite cheap. A single square mile of the ocean contains roughly 120 million tons of sodium chloride. Meng says that this means its theoretical minimum price per kilowatt hour is actually lower than lithium’s.

“The cost point for sodium has been projected to be anywhere from 60 dollars per kilowatt hour to 80,” Meng says. “So about half as much as lithium.”

Thanks to a new research grant from the National Science Foundation, Meng will be able to investigate whether these projections are really feasible, and what it will take to make sodium ion batteries a viable power source. In short, two things really need to happen. The first is that we need to simply understand the chemistry of sodium ion batteries better. The second is that devices as a whole need to get more efficient.

“We’ve been talking about low power electronics for a long time,” she explains. “There’s no reason why, these days, transistors should be so high voltage.”

Low power electronics, coupled with a better understanding of how sodium ion batteries actually work might be enough to help sodium ion overcome the economic headwinds they now face, and help them gain a foothold in the private sector. Several companies have already tried, most notably the Bill Gates-backed Aquion which raised $190 million in venture capital and debt only to go bankrupt in 2017, according to a GreenTechMedia report from the time.

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