High performance flow batteries, based on alkaline
zinc / ferro-
ferricyanide rechargeable (“ZnFe”) and similar flow batteries, may include one or more of the following improvements. First, the battery design has a
cell stack comprising a
low resistance positive
electrode in at least one positive
half cell and a
low resistance negative
electrode in at least one negative
half cell, where the positive
electrode and negative electrode resistances are selected for uniform
high current density across a region of the
cell stack. Second, a flow of
electrolyte, such as
zinc species in the ZnFe battery, with a high level of mixing through at least one negative
half cell in a Zn deposition region
proximate a deposition surface where the
electrolyte close to the deposition surface has sufficiently high
zinc concentration for deposition rates on the deposition surface that sustain the uniform
high current density. The mixing in the flow may be induced by structures such as: conductive and non-conductive meshes; screens; ribbons; foam structures; arrays of cones, cylinders, or pyramids; and other arrangements of wires or tubes used solely or in combination with a
planar electrode surface. Third, the zinc
electrolyte has a
high concentration and in some embodiments has a concentration greater than the equilibrium saturation concentration—the zinc electrolyte is super-saturated with Zn ions.