Redox Targeting-Based Vanadium Redox-Flow Battery

The low energy density and narrow operating temperature window besides the relatively high cost of the vanadium redox-flow battery (VRB) severely hinder its commercial deployment. Herein, in conjunction with low-concentration VO2+/VO2+ catholyte, we introduce a redox targeting-based VRB (RT-VRB) system in which a Prussian blue analogue (PBA), (VO)6Fe(CN)63, is employed as a capacity booster to address the above issues. The charges are reversibly stored in the PBA loaded in the cathodic tank via a redox-targeting reaction with the VO2+/VO2+. Therefore, the concentration of catholyte has been reduced to 0.6 M without sacrificing the capacity. This provides ample room to broaden the operating temperature window of a RT-VRB relative to a conventional VRB. The theoretical volumetric capacity of the PBA could reach 135 Ah/L, which is more than 3 times that of VRB. We anticipate that the RT-VRB system demonstrated here would give credible impetus for VRB chemistry for robust and high-density energy storage applications.