Room‐Temperature Liquid Na–K Anode Membranes

The Na–K alloy is a liquid at 25 °C over a large compositional range. The liquid alloy is also immiscible in the organic‐liquid electrolytes of an alkali‐ion rechargeable battery, providing dendrite‐free liquid alkali‐metal batteries with a liquid–liquid anode‐electrolyte interface at room temperature. The two liquids are each immobilized in a porous matrix. In previous work, the porous matrix used to immobilize the alloy was a carbon paper that is wet by the alloy at 420 °C; the alloy remains in the paper at room temperature. Here we report a room‐temperature vacuum infiltration of the alloy into a porous Cu or Al membrane and a reversible stripping/plating of the liquid alloy with the immobilized organic‐liquid electrolyte; no self‐diacharge is observed since the liquid Na–K does not dissolve into the liquid carbonate electrolytes. The preparation and stripping/plating of the liquid alkali‐metal anode can both now be done safely at room temperature. As an alternative to the high‐temperature Na–S battery with a dendrite‐free molten sodium anode, a room‐temperature liquid alkali‐metal battery with a liquid Na‐K anode and a liquid organic electrolyte is proposed. The liquid Na–K anode membranes can be prepared, used, and recycled at room temperature.