We provide a proof of concept of a lithium battery configuration containing an aqueous cathode in a flow-through mode. A room-temperature, rechargeable alkali-ion battery with a commercially available Li+-ion solid–electrolyte separating a Li0 anode and an organic liquid–carbonate electrolyte on one side and, on the other, an aqueous cathode containing 0.1 M K3Fe(CN)6 has been demonstrated to give high efficiency electrical energy storage at 3.40 V; it is capable of matching the capacity of the Li0 anode if operated with the aqueous cathode in a flow-through mode. The resistance of the solid electrolyte rather than the flow rate of the cathode determined the power density of the test cell. The concept can be used with a more-abundant Na0 anode and a Na+-ion solid electrolyte. The results call for the development of an alkali-ion solid–electrolyte separator with a smaller resistance.
