Boosting zinc-ion storage in hydrated vanadium oxides via migration regulation

Cost-effective and environmentally-friendly aqueous zinc-ion batteries (AZIBs) are promising candidate for large-scale energy storage devices. Layered vanadium oxides with pre-intercalated cations have gained significant attention as cathode materials for AZIBs, because of their excellent performance originated from the pillar effect. However, we observed an unexpected decrease in the interlayer space of vanadium oxides after the pre-intercalation of Cs+. The obtained Cs0.24V2O5·0.19H2O (CsVO) holds a smaller interplanar spacing but delivers excellent rate capacity and high stability (99.5% over 5,000 cycles at 10 A g−1). Systematical ex/in situ characterizations demonstrate the interesting Zn2+/H+ sequential domination mechanism for the CsVO cathode, namely Zn2+ insertion dominates the high voltage (1.6–0.7 V) and H+ insertion dominates the low voltage (0.7–0.2 V). Based on this mechanism, DFT calculation further reveals the unique functions of Cs+, especially the migration regulation of Zn2+.