Carbon-encapsulated V₂O₃ nanorods for high-performance aqueous Zn-ion batteries

Searching for stable cathodes is of paramount importance to the commercial development of low-cost and safe aqueous Zn-ion batteries (AZIBs). V₂O₃ is a good candidate for AZIB cathodes but has unsatisfied cycling stability. Herein, we solve the stability issue of a V₂O₃ cathode by coating a robust carbon shell. Strong evidence was provided that V₂O₃ was oxidized to favorable V₂O₅·nH₂O during charging and the carbon shell could promote the oxidation of V₂O₃ to V₂O₅·nH₂O. The discharge capacity was increased from ∼45 mA h g^-1 to 336 mA h g^-1 after V₂O₃ was oxidized to V₂O₅·nH₂O, indicating a higher Zn²⁺-storage capability of V₂O₅·nH₂O than V₂O₃. In addition, the rate-capability and long-term cycling performance are greatly enhanced after coating carbon shells on the surface of V₂O₃ nanorods. Therefore, the presented strategy of introducing carbon shells and fundamental insights into the favorable role of carbon shells in this study contribute to the advancement of highly stable AZIBs.