Maneuverable B-site cation in perovskite tuning anode reaction kinetics in vanadium redox flow batteries

Abstract

The actual performance of vanadium redox flow batteries (VRFBs) is still significantly constrained by the slow kinetics and major parasitic reactivity of anode issues. Herein, a B-site management strategy of SrBO3 (B = Ti, Zr, Hf) perovskites was proposed to promote the anode reaction jointly explored by experiments and first–principle calculations. As the atomic number of B increases, the enhanced polarity of the B–O bond and the increased oxygen defect can boost the adsorption of vanadium ions, while the weakened orbital hybridization of the B–O bond facilitates the charge transfer of anode reaction. Compared with SrTiO3 and SrZrO3, oversized particles and deformed crystals of SrHfO3 reduce its catalysis. Of SrBO3 perovskites, SrZrO3 stands out in catalysis, owing to its outstanding combination of high hydrophilicity, large surface area, and desired crystal structure. Further, the VRFB using SrZrO3 presents a superior energy efficiency (EE) of 63.2% at 300 mA cm–2 and an increase of 15% in EE compared with the pristine cell at 200 mA cm–2. This work lays the foundation for building the connections between the structural and compositional flexibility and the tunable perovskite properties desirable for vanadium redox reactions.