BATTERIESNew Sodium, Aluminum Battery Aims to Integrate Renewables for Grid Resiliency

A new battery design could help ease integration of renewable energy into the nation’s electrical grid at lower cost, using Earth-abundant metals, according to a study just published in Energy Storage Materials. A research team, led by the Department of Energy’s Pacific Northwest National Laboratory, demonstrated that the new design for a grid energy storage battery built with the low-cost metals sodium and aluminum provides a pathway towards a safer and more scalable stationary energy storage system.

“We showed that this new molten salt battery design has the potential to charge and discharge much faster than other conventional high-temperature sodium batteries, operate at a lower temperature, and maintain an excellent energy storage capacity,” said Guosheng Li, a materials scientist at PNNL and the principal investigator of the research. “We are getting similar performance with this new sodium-based chemistry at over 100 °C [212 °F] lower temperatures than commercially available high-temperature sodium battery technologies, while using a more Earth-abundant material.”

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Imre Gyuk, director of DOE’s Office of Electricity, Energy Storage Program, which supported this research, noted “This battery technology, which is built with low-cost domestically available materials brings us one step closer toward meeting our nation’s clean energy goals.”

The new sodium-based molten salt battery uses two distinct reactions. The team previously reported a neutral molten salt reaction. The new discovery shows that this neutral molten salt can undergo a further reaction into an acidic molten salt. Crucially, this second acidic reaction mechanism increases the battery’s capacity. Specifically, after 345 charge/discharge cycles at high current, this acidic reaction mechanism retained 82.8 percent of peak charge capacity.

The energy that a battery can deliver in the discharge process is called its specific energy density, which is expressed as “watt hour per kilogram” (Wh/kg). Although the battery is in early-stage or  “coin cell” testing, the researchers speculate that it could result in a practical energy density of up to 100 Wh/kg. In comparison, the energy density for lithium-ion batteries used in commercial electronics and electric vehicles is around 170–250 Wh/kg. However, the new sodium-aluminum battery design has the advantage of being inexpensive and easy to produce in the United States from much more abundant materials.

“With optimization, we expect the specific energy density and the life cycle could reach even higher and longer,” added Li.