Interlayer expanded magnesium vanadium bronze for high capacity stable aqueous zinc batteries and method for proton contribution calculation

Magnesium vanadium bronze, MgV₆O₁₆·6H₂O, is demonstrated as a cathode material for aqueous zinc batteries. Its remarkable electrochemical performance is attributed to the hydrated magnesium pillar layer, which enhances zinc ion diffusion into the structure, yielding a high initial discharge capacity of 298 mAh g⁻¹ and capacity retention above 97 % after 300 cycles. Zinc ions and protons are co-intercalated into the MgV₆O₁₆·6H₂O structure, while zinc hydroxide sulfate forms on the surface during the discharge process. Ex-situ X-ray diffraction results and elemental analyses confirm the zinc and proton co-intercalation reaction within the MgV₆O₁₆·6H₂O structure during cycling, providing detailed insights into the electrochemical mechanisms. These findings demonstrate the potential of MgV₆O₁₆·6H₂O as a high-energy cathode material for aqueous zinc batteries and offer a comprehensive understanding of the zinc ion and proton co-intercalation mechanism in the MgV₆O₁₆·6H₂O structure.