Solid buffer materials for electrolyte solutions and flow batteries utilizing same

Abstract

Electrolyte solutions for flow batteries and other electrochemical systems can contain a dissolved iron hexacyanide complex as an active material. Alkaline buffering can be desirable in such electrolyte solutions to promote stability of the active material. However, the buffer material can undesirably decrease solubility of the iron hexacyanide complex to unacceptable levels in some instances. Compositions with increased concentrations of iron hexacyanide can include an aqueous solution containing a dissolved iron hexacyanide complex, and a solid buffer material in contact with the aqueous solution. The solid buffer material is present at an amount greater than that needed to produce a saturation concentration of the solid buffer material in the aqueous solution. Flow batteries and other electrochemical systems can contain the compositions as an electrolyte solution. Electrolyte solutions containing active materials other than an iron hexacyanide complex can also be stabilized by using an appropriate solid buffer material.