Covalency stabilizes high energy vanadium oxide positive electrode for sustainable aqueous zinc-ion batteries

Aqueous zinc-ion batteries are promising sustainable energy-storage systems, yet their practical deployment is hindered by positive electrode structural instability during cycling, which has received less attention. Recognizing the critical role of orbital coupling in metal oxides, we regulate the high-voltage stability of vanadium oxide positive electrodes by modulating the electronic state of V in V₂O₃. Fluorine incorporation into the V-O framework induces asymmetric electron distribution, enhancing V-O orbital overlap and strengthening covalent interactions through reinforced π- and σ-bonding. This increased covalency reduces the basicity of axial oxygen atoms, suppressing proton attack and mitigating structural distortion at high charging voltages. F-V₂O₃ exhibits enhanced cycling stability, retaining 80% capacity over 60,000 cycles at 3 A g^-1. Furthermore, Ah-level pouch cell delivers specific energy (based on all electrode materials) of 95 Wh kg^-1 at 50 mA g^-1. A practical pouch-cell pack with a 3.7 V output successfully powers drones. Here, we show the importance of covalency engineering for stabilizing oxide positive electrodes.