Molten salt batteries, as the name suggests, use molten salts as electrolyte that becomes liquid at high temperatures. Such thermal devices benefit from both high energy and high power densities. Non-rechargeable versions remain dormant until high temperature elevates them. Rechargeable versions have taken roles in industrial power backup, grid storage, and specialist electric vehicles.
A Short History of Molten Salt Batteries
Thermal storage devices emerged during World War II, when German scientist Georg Otto Erb experimented with them to power unmanned aerial weapons. The theory came to the attention of the U.S. military after the war. They used it to energize artillery proximity fuses, and later nuclear weapons.
Much research has gone into developing rechargeable versions since the mid-1960s, using sodium as negative electrode. This highly-reactive metal is attractive, on account of high reduction potential, low weight, relative abundance, and low cost. However, it must be in liquid form to be practical.
Sodium molten salt batteries traditionally operate between 245 and 350 °C (470 and 660 °F). However, other metal combinations have operated between 200 °C (390 °F) and room temperature. We explore a fresh development in the following paragraphs.
A New Direction in Sodium-Sulfur Batteries
A report emerged in very late 2022, concerning a sodium-sulfur battery with four-times-greater capacity than lithium-ion. This material could be derived from natural sea water, rendering the idea even more attractive.
“This could be a breakthrough for renewable energy,” commented lead researcher Shenlong Zhao from University of Sydney. “Our sodium battery has the potential to dramatically reduce costs, while providing four times as much storage capacity as lithium” he claimed.
“This is a significant breakthrough for renewable energy development which, although it reduces costs in the long term, has had several financial barriers to entry.” Sydney Morning Herald announced Australia’s first large-scale sodium-sulfur battery went live at a mine in a semi-arid setting in early May 2023.
Molten salt batteries can function in really harsh climates,” Queensland University of Technology project leader Joshua Watts confirmed. “The battery itself runs hot, so it doesn’t need any air conditioning, so it’s perfect for the desert.”
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