Thermodynamic and Kinetic Suppression of Dissolution in Vanadium-Oxide Cathode for Long-Life Aqueous Zinc Ion...

Vanadium oxides, owing to their multivalent nature and open framework structure, represent highly promising cathode candidates for aqueous zinc-ion batteries (AZIBs). However, their application is constrained by degradation resulting from V-dissolution at the cathode. In this study, Al_1.87V₈O₂₀·4H₂O (AlVO) was synthesized at a current density of 0.5 A g^-1, the capacity retention rate was 91% after 500 cycles. Theoretical calculations indicate that, compared to Ga³⁺, pre-intercalated Al³⁺ increases the solubility energy of AlVO, endowing it with greater intrinsic structural strength. During dynamic cycling, Al³⁺ helps maintain the structural integrity of the material, effectively reducing the increase in system entropy, and regulates Gibbs free energy at the thermodynamic level. Additionally, Al³⁺ significantly reduces the energy barrier for Zn²⁺ migration, resulting in a higher proportion of Zn²⁺ in the AlVO system during Zn²⁺/H⁺ co-intercalation compared to Ga_2.67V₈O₂₀·4H₂O (GaVO). According to Le Chatelier's principle, reducing the H⁺ incorporation ratio in AlVO can effectively inhibit the kinetic process of vanadium dissolution. This study elucidates the dissolution process of vanadium-based cathode materials from the perspectives of thermodynamic principles and kinetic mechanisms, providing a viable approach for designing stable vanadium-based cathodes.