Main observation and conclusionrnThe cathode material plays a crucial role in the performances of aqueous zinc-ion batteries (ZIBs).Herein,we report an ammonium vanadate (NH4V4O10·0.28H2O,NHVO) aqueous ZIB cathode material.The obtained NHVO microflowers manifest high discharge capac-ity (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 Zn2+ intercalation/de-intercalation,which has been demonstrated by various ex-situ and in-situ characterizations.The su-perior electrochemical performance makes the NHVO microflower an ideal candidate cathode material for aqueous ZIBs.