Here we present our recent work in the development of high-performance, low-temperature, molten sodium batteries. Traditional molten sodium batteries operate near 300 °C; lowering their operating temperatures to near the melting point of sodium (98 °C) could significantly decrease costs and increase system-level reliability. At lower temperatures, however, resistances at the anode-separator interface and catholyte-current collector interface become significant. To address these thermally-induced shortcomings, Sn-based coatings on a NaSICON (Na3Zr2Si2PO12) separator are developed, dramatically reducing charge transfer resistances across the molten sodium – NaSICON interface, and enabling battery operation at high current densities. At the catholyte-current collector interface, thermal activation of the carbon current collector is shown to enhance charge transfer, while materials design of the redox-active sodium iodide-metal halide molten salt catholyte further increases battery performance. Together, these methods of improving interfacial charge transport enable long-term cell cycling of a high effiency molten sodium battery at the low temperature of 110 °C.

Materials development for high-performance interfaces in low-temperature molten sodium batteries

ACS Spring Meeting 2021

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