Highly Stable Aqueous Zn‐Ion Batteries Achieved by Suppressing the Active Component Loss in Vanadium‐Based Cathode

Abstract Aqueous zinc–ion batteries (AZIBs) hold significant promise for large‐scale energy storage due to their inherent safety and environmental benefits. However, their practical application is often limited by rapid capacity loss from the dissolution of active cathode materials. Here, an effective strategy is proposed to suppress the active component loss by doping high‐valence Sn 4+ in V 3 O 7 ·H 2 O (Sn–V 3 O 7 ·H 2 O) cathode material to achieve highly stable AZIBs. An impressive capacity retention of 89.3% over 6000 cycles at 5.0 A g −1 and a high specific capacity of 408 mAh g −1 at 0.1 A g −1 are attained. The Sn 4+ doping thermodynamically lowers the formation energy of Sn–V 3 O 7 ·H 2 O and increases the dissolution energy of VO 2 + ions, thereby reinforcing the structural stability and suppressing the vanadium dissolution. Besides, Sn 4+ doping enhances electrical conductivity and broadens Zn 2+ diffusion channels, significantly accelerating Zn 2+ intercalation and deintercalation kinetics. The experimental results are integrated with mechanism analysis and density functional theory calculation to elucidate the dissolution dynamics of V‐based cathodes, and employ X‐ray absorption spectroscopy to reveal the local electronic structures and chemical valences of vanadium during charge/discharge processes, thereby providing comprehensive insights into high‐performance cathode materials for AZIBs.