In situ electrochemical Mn vacancies in CoMnHCF for a high level of zinc storage.

CoMnHCF is utilized in aqueous sodium/zinc mixed ion batteries and exhibits a high reversible capacity with good rate and cycle performances. At 0.05 A g -1 current density, the CoMnHCF can deliver a specific capacity for 180.4 mA h g -1 , and have 99.3% capacity retention after 300 cycles at 0.3 A g -1 . Such high reversible capacity profits from Mn vacancies that generate in situ during the first cycle, which provides more active sites for Zn storage. The de-intercalation of Na + further elevates this good electrochemical performance. Co atoms in the framework are not only involved in the redox reactions, but help to support the structure, thus achieving better cycle stabilities.