Vanadium Oxide Cathode Coinserted by Ni 2+ and NH 4 + for High-Performance Aqueous Zinc-Ion Batteries.

Vanadium-based oxides have garnered significant attention as cathode materials for aqueous zinc-ion batteries (AZIBs) because of their high theoretical capacity and low cost. However, the limited reaction kinetics and poor long-term cycle stability hinder their widespread application. In this paper, we propose a novel approach by coinserting Ni 2+ and NH 4 + ions into V 2 O 5 ·3H 2 O, i.e., NNVO. Structural characterization shows that the coinsertion of Ni 2+ and NH 4 + not only extends the interlayer spacing of V 2 O 5 ·3H 2 O but also significantly promotes the transport kinetics of Zn 2+ because of the synergistic "pillar" effect of Ni 2+ and NH 4 + , as well as the increased oxygen vacancies that effectively lower the energy barrier for Zn 2+ insertion. As a result, the AZIBs with an NNVO electrode exhibit a high capacity of 398.1 mAh g -1 (at 1.0 A g -1 ) and good cycle stability with 89.1% capacity retention even after 2000 cycles at 5.0 A g -1 . At the same time, a highly competitive energy density of 262.9 Wh kg -1 is delivered at 382.9 W kg -1 . Considering the simple scheme and the resultant high performance, this study may provide a positive attempt to develop high-performance AZIBs.