Unveiling the Charge Storage Mechanism of High-Performance LiV₃O₈ Cathode for Mn²⁺/H⁺ Hybrid Batteries

Mn-based energy storage systems are gaining attention as promising candidates for next-generation aqueous batteries, owing to their higher theoretical energy density and capacity compared to conventional Zn-based systems. This advantage is primarily attributed to the lower standard redox potential of the Mn anode (-1.19 V vs SHE) relative to that of Zn (-0.76 V vs SHE). In this study, an Mn²⁺/H⁺ hybrid aqueous battery system utilizing LiV₃O₈ is presented as the cathode material, which delivers a high specific capacity of 204.58 mAh g^-1 and excellent capacity retention of 76.2% after 7,000 cycles. The charge storage mechanism of LiV₃O₈ is thoroughly investigated through structural characterization, as well as diffusion pathway and energy barrier analyses. Proton insertion is identified as the dominant charge carrier and is found to induce the formation of Mn(OH)₂ on the electrode surface, as confirmed by spectroscopic techniques. Notably, the Mn//LiV₃O₈ cell achieved an operating voltage of 1.1-0.2 V higher than that of the conventional Zn//LiV₃O₈ cell. This study underscores the potential of Mn²⁺/H⁺ hybrid systems as next-generation aqueous batteries and offers a comprehensive understanding of the associated reaction mechanisms, providing valuable guidance for the future design of Mn-based aqueous energy storage technologies.