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.