Cationic doping engineering of the ZnV₂O₄ cathode toward fast Zn²⁺ storage

High-performance aqueous zinc-ion batteries (AZIBs) are regarded as a promising candidate for viable energy storage solutions. Exploring suitable cathodes with excellent electrochemical properties plays an important role in this field. Spinel ZnV₂O₄ has been employed as a potential cathode for AZIBs. However, its sluggish electrochemical kinetics impose restrictions on its further development. Hence, Al³⁺ is introduced into the ZnV₂O₄ lattice to accelerate Zn²⁺ diffusion, reduce electron transfer resistance and lengthen the cycling life. The structural analyses confirm that Al³⁺ is successfully doped into ZnV₂O₄ without any impurity and with improved structural stability. The electrochemical measurements and corresponding kinetic analyses reveal that the resulting Al-ZnV₂O₄ cathode exhibits significantly enhanced electrochemical performance and reaction kinetics. This is demonstrated by its excellent cycling stability (215 mA h g^-1 at 100 mA g^-1), remarkable rate capability (91 mA h g^-1 at 20 A g^-1), improved Zn²⁺ diffusion coefficient (10^-15 to 10^-13 cm² s^-1) and reduced charge transfer resistance (85 Ω).