Enabling High-Performance Zinc-Ion Batteries with Selenium-Doped VO2 Cathodes: Insights into Structural Regulation and Kinetics Enhancement

Vanadium dioxide (VO 2 ) has gained significant attention as a promising cathode for aqueous zinc-ion batteries (AZIBs), benefiting from its multivalent characteristics and structurally versatile frameworks. Nevertheless, its practical implementation is hampered by strong electrostatic interactions and sluggish reaction kinetics, which collectively restrict the achievable performance of vanadium-based electrodes. In this study, we implement an anion doping strategy by utilizing selenium (Se) to concurrently engineer accelerated electrochemical kinetics. As a result, the Se-doped VO 2 electrode achieves an approximately order-of-magnitude improvement in the Zn 2+ diffusion coefficient (up to ∼10 –13 cm 2 s –1 ) and a low charge transfer activation (345 meV) compared to those of pristine VO 2 and P-doped VO 2 . The Se-VO 2 cathode delivers a remarkable cycling stability, retaining a discharge capacity of 173 mA h g –1 after 2000 cycles at 4 A g –1 . It also exhibits superior rate capability, sustaining 305 mA h g –1 even at a high rate of 20 A g –1 . Ex-situ structural analyses revealed that Se-VO 2 cathode undergoes a phase transformation to Zn 3+ x (OH) 2 V 2 O 7 ·2H 2 O during the initial discharge, followed by amorphization in the subsequent charge process. This amorphous configuration is shown to be highly favorable for Zn 2+ storage within the VO 2 lattice. This work demonstrates that rational anion doping can effectively modulate the electron transfer and Zn 2+ diffusion properties of oxide cathodes, offering a viable pathway toward long-lasting AZIBs with high power density.