Confined Mn Ions Enhance Charge Transport for High-Performance Hydrated Vanadium Oxide Cathode

Hydrated vanadium oxides with high theoretical specific capacities and open crystal structures are promising cathodes for aqueous Zn-ion batteries (AZIBs). However, the sluggish Zn2+ diffusion and poor electrochemical stability remain challenges in battery applications. In this work, Mn ions are effectively confined within the interlayer of the layered vanadium oxide nanobelts through a preintercalation mechanism. The confined Mn ions serve as structural pillars to extend the interlayer spacing, connect adjacent layers, and partially reduce pentavalent vanadium cations to tetravalent states. This expansion of interlayer spacing reduces electrostatic interactions, while the metal cations enhance electrical conductivity and facilitate charge transport. Consequently, it significantly promotes the rapid and reversible intercalation or (de)intercalation of Zn2+ in AZIBs. The MnVO cathode demonstrates a reversible capacity of 549 mAh g–1 at 0.1 A g–1 and maintains a capacity retention of 91% after 100 cycles at a low current density of 0.2 A g–1. Even after 1000 cycles at 2 A g–1, the MnVO cathode displays stable cycling behavior while maintaining a high specific capacity of 350 mA h g–1 (almost 100% capacity retention). The electrochemical reaction kinetics and Zn2+ storage mechanism are investigated in detail.