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

Developing high capacity and stable cathodes is a key to successful commercialization of aqueous Zn-ion batteries (ZIBs). Pure layered V O has a high theoretical capacity (585 mAh g ), but it suffers severe capacity decay. Pre-inserting cations into V O can substantially stabilize the performance, but at an expense of lowered capacity. Here we show that an atomic layer deposition derived V O 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 V O atomic layers into Zn V O (OH) ⋅2 H 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 V O -dissolution mechanisms for different Zn-salt aqueous electrolytes and their implications to the cycle stability.