Co-intercalation strategy of constructing partial cation substitution of ammonium vanadate {(NH 4 ) 2 V 6 O 16 } for stable zinc ion storage.

Recently, aqueous zinc-ion batteries have become a hot research topic in the field of grid-scale application, which can be attributed to their low-cost, aqueous electrolyte and dominant theoretical reversible capacity. Nevertheless, the lack of suitable cathode materials greatly hinders the development of aqueous zinc-ion batteries. In this work, we adopt a simple one-step synthesis strategy to prepare (NH 4 ) 2 V 6 O 16 with an intercalation of Na + and H 2 O, which exhibits a novel crystal structure in which the ammonium ion, crystal water, and sodium ion co-locate in the V 3 O 8 layers. The co-intercalation not only effectively enhances the binding energy between V-O layers to suppress vanadium dissolution but also successfully improves the structural stability to alleviate the structural collapse during the cyclic process. As result, (NH 4 ) 2 V 6 O 16 with the intercalation of crystal water and Na + presents a remarkable reversible discharge capacity of 423.9 mA h g -1 after 90 cycles at 0.1 A g -1 with an excellent energy density of 350.3 W h kg -1 and demonstrates an outstanding specific capacity of 182.5 mA h g -1 at the high current density of 5 A g -1 upon 1400 cycles during the ultra-wide voltage window of 0.1-2.0 V.