High‐Performance Mn‐Based Hybrid Aqueous Batteries Enabled by Interlayer‐Expanded Magnesium Vanadium Bronze Cathode

Manganese-based ion batteries exhibit a relatively low redox potential (-1.19 V vs SHE) along with high theoretical capacity and excellent capacity retention characteristics, making them promising for next-generation batteries. In this study, a high-performance manganese hybrid aqueous battery with an expanded interlayer spacing is designed and fabricated using MgV₆O₁₆·7H₂O (MgVO) as the cathode material and manganese metal as the anode. The fabricated Mn metal battery achieves an initial discharge capacity of 195.3 mAh g^-1 (with Mn metal anode) at a current density of 0.1 A g^-1 with 1.19 V and exhibits excellent capacity retention of even after 200 cycles at a current density of 0.4 A g^-1. Furthermore, detailed structural behavior and operational mechanisms of ions within the MgVO electrode are elucidated through comprehensive analyses of the crystal structure, ion diffusion pathways, and activation energy calculations. Compared to zinc-based aqueous batteries (-0.76 V vs SHE), the manganese-based system demonstrates a ≈0.43 V higher theoretical operating voltage, which is consistent with the experimental observations. This study not only confirms the potential of MgVO as a promising cathode material for next-generation manganese aqueous batteries but also provides valuable insights for the performance enhancement and design optimization of manganese-based aqueous battery systems.