Ca/Ni Codoping Enables the Integration of High-Rate and High-Capacity Zn-Ion Storage Performances for Layered Hydrated Vanadate

Hydrated Metal Vanadate Heterostructures as Cathode Materials for Stable Aqueous Zinc-Ion Batteries

Aqueous zinc ion batteries (AZIBs) have received a lot of attention in electrochemical energy storage systems for their low cost, environmental compatibility, and good safety. However, cathode materials still face poor material stability and conductivity, which cause poor reversibility and poor rate performance in AZIBs. Herein, a heterogeneous structure combined with cation pre-intercalation strategies was used to prepare a novel CaV6O16·3H2O@Ni0.24V2O5·nH2O material (CaNiVO) for high-performance Zn storage. Excellent energy storage performance was achieved via the wide interlayer conductive network originating from the interlayer-embedded metal ions and heterointerfaces of the two-phase CaNiVO. Furthermore, this unique structure further showed excellent structural stability and led to fast electron/ion transport dynamics. Benefiting from the heterogeneous structure and cation pre-intercalation strategies, the CaNiVO electrodes showed an impressive specific capacity of 334.7 mAh g-1 at 0.1 A g-1 and a rate performance of 110.3 mAh g-1 at 2 A g-1. Therefore, this paper provides a feasible strategy for designing and optimizing cathode materials with superior Zn ion storage performance.

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 V2O5·3H2O, i.e., NNVO. Structural characterization shows that the coinsertion of Ni2+ and NH4+ not only extends the interlayer spacing of V2O5·3H2O 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.