Unveiling Intercalation Chemistry via Interference‐Free Characterization Toward Advanced Aqueous Zinc/Vanadium Pentoxide Batteries

Aqueous Zn/V₂O₅ batteries are featured for high safety, low cost, and environmental compatibility. However, complex electrode components in real batteries impede the fundamental understanding of phase transition processes and intercalation chemistry. Here, model batteries based on V₂O₅ film electrodes which show similar electrochemical behaviors as the real ones are built. Advanced surface science characterizations of the film electrodes allow to identify intercalation trajectories of Zn²⁺, H₂O, and H⁺ during V₂O₅ phase transition processes. Protons serve as the vanguard of intercalated species, facilitating the subsequent intercalation of Zn²⁺ and H₂O. The increase of capacity in the activation process is mainly due to the transition from V₂O₅ to more active V₂O₅·nH₂O structure caused by the partial irreversible deintercalation of H₂O rather than the increase of active sites induced by the grain refinement of electrode materials. Eventually, accumulation of Zn species within the oxide electrode results in the formation of inactive (Zn₃(OH)₂V₂O₇·2H₂O) structure. The established intercalation chemistry helps to design high-performance electrode materials.