Fe / Fe Flow Battery

This chapter describes the operating principles and key features of the all-iron flow battery (IFB). This energy storage approach uses low-cost iron metal (Fe) ions for both the positive and negative electrode reactions thereby requiring less stringent membrane properties. The chemistry of the positive and negative electrode reactions is discussed along with electrolyte factors affecting performance and membrane separators. Methods of rebalancing the electrolytes following proton loss via the negative electrode parasitic reaction on charge are described. A rudimentary comparison of the estimated costs of the IFB and the vanadium flow battery (FB) is summarized and a discussion of recent commercialization activities is given. A slurry electrode approach is described to overcome cell capacity limit caused by the iron plating reaction at the negative electrode. The IFB is a promising approach for low-cost large-scale energy storage.