Long-duration energy storage is increasingly recognized as the principal limitation that is preventing the widespread use of renewables on the grid. This talk will present new flow battery electrolytes that use of metal ions coordinated to organic ligands called chelates. One particular class of chelates, called polyaminocarboxylates are known to bind metal ions very strongly and are used for a wide variety of industrial applications including textiles, water treatment, paper pulping, agriculture, consumer products, and medicine. We found that a chelate called PDTA, differing from EDTA by just one additional carbon atom, was better suited for coordination to chromium. By tightly coordinating to the chromium ion, the chelate prevents the electrons stored on the metal from reacting with the water in the electrolyte. This approach has allowed us to create some of the highest voltage aqueous flow batteries and allows them to be operated near neutral pH. In particular, we have demonstrated a chelated iron-chromium flow battery operating at pH 9 with 1.62 V equilibrium potential, stable cycling over 160 hours at 100 mA/cm2.