Enhanced Electrochemical Performance and Cycling Stability of the (NH4)8[VIV12VV7O41(OH)9]·11H2O Cathode in Aqueous Zinc Ion Batteries

Although vanadium-based compounds possess several advantageous characteristics, such as multivalency, open structure, and high theoretical specific capacity, which render them highly promising candidates for cathode materials in aqueous zinc ion batteries (AZIBs), their large-scale application still necessitates addressing the challenges posed by slow kinetics resulting from low conductivity and capacity degradation caused by material dissolution. Therefore, we have successfully synthesized high-purity mixed multivalent (NH₄)₈[V^IV₁₂V^V₇O₄₁(OH)₉]·11H₂O (NVO) crystalline materials via a liquid-phase precipitation modulation method and employed it as an innovative AZIB cathode material for the first time. It exhibits a remarkable reversible specific capacity of 240 and 102.2 mAh g^-1 after undergoing 1000 cycles at current densities of 1 and 5 A g^-1, respectively, highlighting its exceptional cycling stability and electrochemical performance. The results from cyclic voltammetry (CV) and GITT tests demonstrate that the dominant factor influencing the charge storage is the pseudocapacitive behavior, which is accompanied by an exceptionally high diffusion coefficient of Zn²⁺ at a rate of 10^-10 cm² s^-1. The highly reversible intercalation-deintercalation of Zn²⁺ in NVO/Zn cells is demonstrated through ex-situ TEM, XRD, and XPS analyses. This work provides a benchmark for the development of high-performance POV electrode materials.