A step ahead for liquid metal batteries and renewable energy

Image showing three vertical layers of material in a glass container.

A physical model of the liquid metal battery at room temperature, in a glass container. (Image: Felice Frankel)

One of the challenges facing some renewable energy sources — such as solar or wind power — is that our demand for electricity stays high when the sun’s not shining or the wind’s not blowing.

MIT’s Donald Sadoway — instructor for our popular OCW Scholar course 3.091SC Introduction to Solid State Chemistry — has been working for several years on a high-tech liquid metal battery system to help bridge between electricity supply and demand. Such batteries could store excess generated energy when it’s available, and pump it back into the electric grid when it’s needed. The promise of this research landed Prof. Sadoway on Time magazine’s 2012 list of “the 100 most influential people in the world.”

The technology continues to progress. This month, Prof. Sadoway and colleagues announced a substantially improved battery formulation, which could make the cost of battery-backed renewable energy more competitive with fossil-fuel sources. MIT News reports:

Donald Sadoway and colleagues have already started a company to produce electrical-grid-scale liquid batteries, whose layers of molten material automatically separate due to their differing densities. But the new formula — published in the journal Nature by Sadoway, former postdocs Kangli Wang and Kai Jiang, and seven others — substitutes different metals for the molten layers used in a battery previously developed by the team.

Sadoway, the John F. Elliott Professor of Materials Chemistry, says the new formula allows the battery to work at a temperature more than 200 degrees Celsius lower than the previous formulation. In addition to the lower operating temperature, which should simplify the battery’s design and extend its working life, the new formulation will be less expensive to make, he says.

The battery uses two layers of molten metal, separated by a layer of molten salt that acts as the battery’s electrolyte (the layer that charged particles pass through as the battery is charged or discharged). Because each of the three materials has a different density, they naturally separate into layers, like oil floating on water.

The original system, using magnesium for one of the battery’s electrodes and antimony for the other, required an operating temperature of 700 C. But with the new formulation, with one electrode made of lithium and the other a mixture of lead and antimony, the battery can operate at temperatures of 450 to 500 C. Read more.

Prof. Sadoway’s innovative work on one of today’s most pressing needs will come as no surprise to anyone that’s watched his lectures in 3.091SC Introduction to Solid State Chemistry. Bill Gates called them “the best chemistry lessons anywhere.”

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