Supercritical Solvothermal Synthesis of Spinel ZnV ₂ O ₄ /Porous Carbon Composite Cathodes for Aqueous Zinc‐Ion Batteries

ABSTRACT

The electrochemical performance of vanadium‐based oxide cathodes in aqueous zinc‐ion batteries has long been constrained by their intrinsically low electronic conductivity, severe vanadium dissolution, and prolonged synthesis procedures. To address these limitations, a supercritical solvothermal strategy is developed for the rapid fabrication of a high‐performance spinel‐structured ZnV ₂ O ₄ /porous carbon (ZnV ₂ O ₄ /PRC) composite. Benefiting from the excellent mass transfer and heat transfer characteristics and mild reducing capability of supercritical ethanol, this approach effectively suppresses the formation of hydrated zinc vanadate phases, thereby significantly shortening the reaction time required for ZnV ₂ O ₄ formation. Meanwhile, the introduction of a porous carbon (PRC) framework provides efficient electrolyte penetration pathways, reduces the interparticle diffusion resistance of Zn ²⁺ ions, and minimizes the direct contact between ZnV ₂ O ₄ and the electrolyte. As a result, the electronic conductivity of the composite is substantially enhanced, Zn ²⁺ transport kinetics are accelerated, and vanadium dissolution is significantly mitigated. Owing to these combined advantages, the ZnV ₂ O ₄ /PRC cathode delivers a high reversible capacity of 470 mAh g ⁻¹ at 0.1 A g ⁻¹ and retains 172 mAh g ⁻¹ after 5000 cycles at a high current density of 10 A g ⁻¹ , demonstrating outstanding long‐term cycling stability.