Abstract: An electrolyte solution including a redox active species and a buffer is described. The concentration of both the redox active species and the buffer in the electrolyte solution is greater than 0.4 M. The pH of the electrolyte solution is in the range of from 5 to 11. In some embodiments of the electrolyte solution, the concentration of the buffer is equal to or greater than the concentration of the redox active species.

Abstract: An aqueous electrolyte solution having an increased or decreased concentration of ferrocyanide is described. The increased or decreased concentration of ferrocyanide in the aqueous electrolyte solution is possible by virtue of the inclusion in the electrolyte solution of a polyion additive. The ferrocyanide component of the aqueous electrolyte solution may be sodium ferrocyanide, potassium ferrocyanide, or a combination thereof. The polyion polymer additive component of the aqueous electrolyte solution may a polycation or a polyanion. An aqueous electrolyte solution having an increased or decreased concentration of ferricyanide is also described.