Intercalant-induced V t 2 g orbital occupation in vanadium oxide cathode toward fast-charging aqueous zinc-ion batteries

This is the authors' abstract. We don't add key points for this paper.

Intercalation-type layered oxides have been widely explored as cathode materials for aqueous zinc-ion batteries (ZIBs). Although high-rate capability has been achieved based on the pillar effect of various intercalants for widening interlayer space, an in-depth understanding of atomic orbital variations induced by intercalants is still unknown. Herein, we design an NH₄⁺-intercalated vanadium oxide (NH₄⁺-V₂O₅) for high-rate ZIBs, together with deeply investigating the role of the intercalant in terms of atomic orbital. Besides extended layer spacing, our X-ray spectroscopies reveal that the insertion of NH₄⁺ could promote electron transition to 3dxy state of V t2g orbital in V₂O₅, which significantly accelerates the electron transfer and Zn-ion migration, further verified by DFT calculations. As results, the NH₄⁺-V₂O₅ electrode delivers a high capacity of 430.0 mA h g⁻¹ at 0.1 A g⁻¹, especially excellent rate capability (101.0 mA h g⁻¹ at 200 C), enabling fast charging within 18 s. Moreover, the reversible V t2g orbital and lattice space variation during cycling are found via ex-situ soft X-ray absorption spectrum and in-situ synchrotron radiation X-ray diffraction, respectively. This work provides an insight at orbital level in advanced cathode materials.