Scientists may have solved how to use calcium in liquid metal batteries for large-scale energy storage system applications.
While calcium is ideal for negative electrodes due to its low electronegativity, double valencey (compared to lithium), abundance and low cost, its high melting temperature and high solubility in molten salts when used as a negative electrode are a problem.
Led by Ambri’s chief scientific officer and Massachusetts Institute of Technology (MIT) professor Donald Sadoway, scientists have shown how using a binary electrolyte along with a magnesium-alloyed negative electrode solves the solubility issue and reduces operating temperature of the cell.
The temperature achieved was about 300 degrees less than that of pure calcium, while retaining the high voltage advantage, said the paper.
Alongside the magnesium-calcium discovery, the scientists have come up with a new form of salt for the electrolyte that consists of a mix of lithium chloride and calcium chloride, which prevents the magnesium-calcium alloy from dissolving so easily.
While working on the new electrolyte, the scientists also discovered that rather than a single ‘itinerant ion’ passing it in a rechargeable battery, in this case, multiple ions contributed to the flow, boosting the battery’s overall energy output.
“There’s an irony here,” says Sadoway. “If you’re trying to find high-purity ore bodies, magnesium and calcium are often found together and it takes great effort and energy to purify one or the other.
“But since the material that will be needed for the electrode in these batteries is a mixture of the two, it may be possible to save on the initial materials costs by using ‘lower’ grades of the two metals that already contain some of the other.”
Picture: David Bradwell, Ambri’s CTO, with his company’s liquid metal battery storage system
