text: Quinone molecules have been used as anolytes in alkaline AROFBs. Another anolyte candidate is fluorenone, reengineered to increase its water solubility.  A reversible ketone (de)hydrogenation demonstration cell operated continuously for 120 days over 1,111 charging cycles at room temperature without a catalyst, retaining 97% percent capacity. The cell offers more than double the energy density of vanadium-based systems. The major challenge for alkaline AORFBs is the lack of a stable catholyte, holding their energy densities below 5 Wh/L. All reported alkaline AORFBs use excess potassium ferrocyanide catholyte because of the stability issue of ferrocyanide in alkaline solutions.
  Metal-organic flow batteries use organic ligands to improve the properties of redox-active metals. The ligands can be chelates like EDTA, and can enable the electrolyte to be in neutral or alkaline conditions under which metal aquo complexes would otherwise precipitate. By blocking the coordination of water to the metal, organic ligands can inhibit metal-catalyzed water-splitting reactions, resulting in higher voltage all-aqueous systems. For example, the use of chromium coordinated to 1,3-propanediaminetetraacetate (PDTA), gave cell potentials of 1.62 V vs. ferrocyanide and a record 2.13 V vs. bromine. Metal-organic flow batteries may be known as coordination chemistry flow batteries, which represents the technology behind Lockheed Martin's Gridstar Flow technology.