A High Performing Zn-Ion Battery Cathode Enabled by In Situ Transformation of V₂ O₅ Atomic Layers

Developing high capacity and stable cathodes is a key to successful commercialization of aqueous Zn-ion batteries (ZIBs). Pure layered V₂ O₅ has a high theoretical capacity (585 mAh g^-1 ), but it suffers severe capacity decay. Pre-inserting cations into V₂ O₅ can substantially stabilize the performance, but at an expense of lowered capacity. Here we show that an atomic layer deposition derived V₂ O₅ can be an excellent ZIB cathode with high capacity and exceptional cycle stability at once. We report a rapid in situ on-site transformation of V₂ O₅ atomic layers into Zn₃ V₂ O₇ (OH)₂ ⋅2 H₂ O (ZVO) nanoflake clusters, also a known Zn-ion and proton intercalatable material. High concentration of reactive sites, strong bonding to the conductive substrate, nanosized thickness and binder-free composition facilitate ionic transport and promote the best utilization of the active material. We also provide new insights into the V₂ O₅ -dissolution mechanisms for different Zn-salt aqueous electrolytes and their implications to the cycle stability.