Better engineering layered vanadium oxides for aqueous zinc‐ion batteries: Going beyond widening the interlayer spacing

Abstract Aqueous zinc‐ion batteries (ZIBs) are regarded as among the most promising candidates for large‐scale grid energy storage, owing to their high safety, low costs, and environmental friendliness. Over the past decade, vanadium oxides, which are exemplified by V2O5, have been widely developed as a class of cathode materials for ZIBs, where the relatively high theoretical capacity and structural stability are among the main considerations. However, there are considerable challenges in the construction of vanadium‐based ZIBs with high capacity, long lifespan, and excellent rate performance. Simple widenings of the interlayer spacing in the layered vanadium oxides by pre‐intercalations appear to have reached their limitations in improving the energy density and other key performance parameters of ZIBs, although various metal ions (Na+, Ca2+, and Al3+) and even organic cations/groups have been explored. Herein, we discuss the advances made more recently, and also the challenges faced by the high‐performance vanadium oxides (V2O5‐based) cathodes, where there are several strategies to improve their electrochemical performance ranging from the new structural designs down to sub‐nano‐scopic/molecular/atomic levels, including cation pre‐intercalation, structural water optimization, and defect engineering, to macroscopic structural modifications. The key principles for an optimal structural design of the V2O5‐based cathode materials for high energy density and fast‐charging aqueous ZIBs are examined, aiming at paving the way for developing energy storage designed for those large scales, high safety, and low‐cost systems.