Vanadium Oxide Cathode Coinserted by Ni2+ and NH4 + 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 Ni2+ and NH4+ ions into V2O5<middle dot>3H(2)O, i.e., NNVO. Structural characterization shows that the coinsertion of Ni2+ and NH4+ not only extends the interlayer spacing of V2O5<middle dot>3H(2)O but also significantly promotes the transport kinetics of Zn2+ because of the synergistic "pillar" effect of Ni2+ and NH4+, as well as the increased oxygen vacancies that effectively lower the energy barrier for Zn2+ 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.