Development of structurally stable vanadium oxide cathodes featuring tunable ion transport channels via suppressing VO distortion for aqueous zinc ion batteries

Ionic pre-insertion is considered to be an effective method of modulating the interlayer structure of vanadium oxides, allowing for greater interlayer spacing and more active site exposure. However, the pre-inserted ions inevitably compete with the V atoms for the O atoms, leading to irreversible stretching distortion of the V O bond and thus reducing the stability of vanadium oxides. Herein, we inhibit the competitive displacement of oxygen atoms in vanadium oxides due to pre-inserted NH 4 + ions by utilizing Na + instead, and thus the obtained NaNHVO demonstrated impressive cycling stability (capacity retention of 86 % for 10,000 cycles at 10 A g −1 ), fast ion inserted/de-inserted kinetics, and highly competitive specific discharge capacity (465.6 mAh g −1 at 0.1 A g −1 ). The variation of the V O bond lengths of NaNHVO and its unique ion transport pathway are verified by a combination of DFT calculations and experiments. In addition, the electrochemical energy storage mechanism of Zn 2+ /H + co-storage of NaNHVO is determined by tracking the changes in the electrode structure at different charging-discharging stages. This work provides new insightful ideas for improving the ion pre-insertion method and thus designing rational layered vanadium oxide electrode materials.