Expanding Layer Spacing of Carbon‐Coated Vanadium Oxide via Ammonium Ions for Fast Electrochemical Kinetics in Aqueous Zinc‐Ion Batteries

Aqueous zinc‐ion batteries (AZIBs) have recently shown promise as prospective energy storage systems owing to their eco‐friendliness, low price, high security, and reversible storage. However, low specific capacity and the lack of cathode materials with a long life severely restrict the development of AZIBs. Herein, nanoflower‐like vanadium oxide nanoribbons are rapidly synthesized using a microwave‐assisted solvothermal method, and the layer spacing of synthesized nanoribbons is subsequently expanded with ammonium via high‐temperature calcination in an NH 3 atmosphere. The increased layer spacing of vanadium oxide facilitates the intercalation/extraction of Zn 2+ and accelerates the electrochemical kinetics, resulting in a highly reversible pseudocapacitive contribution (71% at a scan rate of 1 mV s −1 ). The ammonium‐embedded V 2 O 5 with the carbon‐coated NH 4 V 4 O 10 /C (NHVO/C) cathode shows a high specific capacity (458.6 mAh g −1 at 0.1 A g −1 ) and excellent cycling stability (about 90% capacity retention after 2800 cycles at 10 A g −1 ), which is superior to most cathode materials for AZIBs. Furthermore, reversible Zn 2+ intercalation/extraction in the NHVO/C cathode during electrochemical reactions is elucidated through in situ and ex situ material characterization. The findings are expected to inspire the development of advanced vanadium‐based cathode materials for green, safe, and dependable energy storage devices for commercial applications.