Low-temperature molten sodium batteries

Abstract

Low-temperature molten sodium batteries show remarkable promise as the kind of low-cost, large-scale, reliable energy storage technology which is key to enabling a sustainable, safe, and resilient electric grid. Here, we describe a combination of cathode chemistry and engineered interfaces needed to reduce the molten sodium battery operating temperature from ∼300 °C to near 100 °C. This approach involves the development of a fully molten, inorganic sodium battery comprising a sodium anode, a NaSICON (Na3Zr2Si2PO12) solid electrolyte separator, and a sodium iodide/aluminum bromide liquid catholyte operated at 110 °C. Battery performance is greatly improved by the application of a Sn coating on the anode-facing side of the NaSICON electrolyte and by the activation of a carbon felt current collector, together enabling the low-temperature molten sodium battery to achieve 200 cycles at 110 °C. The advancement of the low operating temperature molten sodium battery shows promise as a low-cost, large-scale energy storage system.