Liquid Metal Batteries

Liquid Metal Batteries

Sodium-Sulfur Battery (NaS battery)

Sodium-sulfur batteries are a partially molten-metal battery that can be used to store energy for later use in renewable applications, load leveling, or provide a backup source for communities similar to the BESS system in Fairbanks. This battery is up to 90% efficient and around 70-75% efficient after AC/DC conversion. Most batteries of this type are constructed in large cylindrical units with a solid electrolyte that separates molten metallic sodium and sulfur. During discharge, the molten sodium releases electrons to sulfur which forms negative sulfur ions.1 These batteries can be built with relativly cheap, earth abundant, materials. However, the active ingredients, sodium and sulfur are highly corrosive which causes degradation within the battery, shortening their life. Additionally, operating temperatures can be above 300 degrees Fahrenheit, limiting them to larger size applications.2

Currently there are NaS batteries in development that could have lower operating temperatures.

Magnesium-Antimony Liquid Metal Battery (Mg-Sb)

The Magnesium-Antimony Liquid Metal Battery is a new system that is under development, and has successfully proven itself in lab trials. These batteries could have potential to be a low cost alternative to current battery technology. The battery was developed a professor, students and researchers at Massachusetts Institute of Technology, who, in 2010, after the successful lab experiments, created the Liquid Metal Battery Coporation to commercialize the technology.3

This battery utilizes two active ingredients, a layer of magnesium (Mg) and a layer of antimony (Sb). They are separated by a molten salt electrolyte. Because the metals have different densities and metals and salt do not mix, there is no need for solid separators between the electrodes. This eliminates weight and allows more space for the active materials. To produce current, the magnesium loses two electrons, which migrate across the salt and accepts two electrons from the antimony. This forms an alloy. To reverse charge the battery, you reverse the charge.4

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