Tailored phase-valence coupling by aliovalent substitution toward high-rate and stable vanadium oxide cathodes for aqueous zinc-ion batteries

초록

Vanadium oxide cathodes for aqueous zinc-ion batteries (AZIBs) often suffer from sluggish Zn2+ transport and structural instability during cycling. Here, we propose an aliovalent substitution-driven phase-valence coupling strategy to construct a ternary V2O5/VO2/Al2O3 (AlVO) composite via a one-step hydrothermal route followed by low-temperature calcination. Rather than conventional Al doping, partial substitution of Al3+ for V5+/V4+ induces charge compensation and regulates the coexistence of VO2, V2O5, and Al2O3 domains. By fixing the Al precursor and tuning the vanadium concentration, an optimized composition forms a balanced crystalline-defective framework with strong Al-O-V coordination, which stabilizes the VOx lattice, reduces VO2 surface oxidation, and improves interfacial charge transport. As a result, the optimized AlVO-2 delivers a reversible capacity of 613 mAh g-1 after 100 cycles at 0.5 A g-1, demonstrates high-rate performance of 313 mAh g-1 at 10 A g-1, and retains 397 mAh g-1 after 2500 cycles at 5 A g-1. Electrochemical impedance spectroscopy (EIS), distribution of relaxation time (DRT) analysis, and temperature-dependent EIS with Arrhenius fitting reveal accelerated kinetics and reduced charge-transfer barriers. Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirm highly reversible Zn2+/H+ intercalation accompanied by stable V5+/V4+ transitions. Therefore, this work establishes aliovalent substitution-mediated compositional engineering as a robust route to high-rate, durable vanadium oxide cathodes for AZIBs.

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