Supplementary file 1_Engineering the structural and electronic properties of VO2 through Fe substitution for high-performance aqueous zinc-ion batteries.docx

Among the numerous cathodes for AZIBs, VO₂ is a promising candidate due to its tunnel-like structure and high theoretical capacity; however, its practical application is limited by its low electronic conductivity. To address this issue, doping with several transition metals has been attempted; however, exploration of Fe doping is rare despite its cost-effectiveness and abundance.

Herein, a series of Fe-substituted VO₂ cathodes (Fe_xV_1-xO₂: x = 0.15, 0.25, and 0.35) have been synthesized via a simple one-step hydrothermal method and systematically evaluated for AZIB applications. PXRD studies indicate a noticeable lattice expansion upon Fe substitution, providing relatively wider pathways for Zn²⁺ transport within the cathode framework. Among the investigated compositions, Fe_0.25V_0.75O₂ exhibited the best electrochemical performance, delivering a high specific capacity of 380.11 mAh g^-1 at 0.1 A g^-1, retaining 56% capacity at 5 A g^-1, and maintaining 82.75% capacity retention after 500 cycles at 2 A g^-1, significantly outperforming the pristine VO₂ cathode.