Regulating interfacial water structure to suppress vanadium dissolution in aqueous zinc-ion batteries

Vanadium-based cathodes in aqueous zinc-ion batteries (AZIBs) suffer from severe capacity fading due to their high solubility in weakly acidic zinc salt electrolytes. In this work, we propose a novel electrolyte formulation by introducing tetrahydrofurfuryl alcohol (THFA) as an additive to a 2 M zinc trifluoromethanesulfonate (Zn(OTf)₂) solution to effectively suppress the dissolution of V₆O₁₃·nH₂O (VOH) cathodes. THFA preferentially adsorbs onto the cathode surface, displacing interfacial water and mitigating water-induced degradation of VO bonds. Simultaneously, the strong interaction between THFA and Zn²⁺ alters the solvation structure, reducing the population of active water molecules coordinated to Zn²⁺ ions. These synergistic effects significantly inhibit vanadium dissolution and enhance interfacial stability. Benefiting from this interfacial engineering strategy, the VOH cathode delivers a high specific capacity of 477.7 mAh g^-1 at 0.5 A g^-1 and achieves excellent capacity retention of 82.6 % after 200 cycles, in stark contrast to 45.9 % for the additive-free system. Moreover, long-term cycling tests demonstrate outstanding durability, with 71.4 % capacity retention after 10,000 cycles at 10 A g^-1, compared to only 37.5 % without the additive. This study offers a promising approach to mitigate cathode dissolution via electrolyte design and provides a generalizable strategy for improving the cycling stability of vanadium-based AZIBs.