Ammonium Ion and Structural Water Co‐Assisted Zn2+ Intercalation/De‐Intercalation in NH4V4O10∙0.28H2O†

Main observation and conclusion The cathode material plays a crucial role in the performances of aqueous zinc‐ion batteries (ZIBs). Herein, we report an ammonium vanadate (NH 4 V 4 O 10 ∙0.28H 2 O, NHVO) aqueous ZIB cathode material. The obtained NHVO microflowers manifest high discharge capacity (410 mA·h∙g –1 at 0.2 A∙g –1 ), long‐term durability (76% capacity retention over 500 cycles), as well as ideal rate performance (112 mA·h∙g –1 at 10 A∙g –1 ). The impressive electrochemical performance can be attributed to the ammonium ion and structural water co‐assisted Zn 2+ intercalation/de‐intercalation, which has been demonstrated by various ex‐situ and in‐situ characterizations. The superior electrochemical performance makes the NHVO microflower an ideal candidate cathode material for aqueous ZIBs.