Hollow Mn–Co–O@C Yolk–Shell Microspheres with Carbon Shells as Cathodes Derived from a Double-Metal MOF for Aqueous Zinc-Ion Batteries

Manganese-based cathodes are promising candidates for aqueous zinc-ion batteries (AZIBs) due to their high-voltage platform, low-price, environmental friendliness, high theoretical capacity, and non-toxicity. Unfortunately, their application is restricted due to issues such as manganese dissolution, poor electrical conductivity, and poor volume expansion, which lead to unsatisfactory rate performance and fast capacity decay. Hollow Mn–Co–O@C yolk–shell microspheres with carbon shells were fabricated from self-assembled Mn–Co-metal–organic frameworks via combining facile normal temperature and annealing methods. Mn–Co–O@C achieved an excellent specific capacity of 401 mA h g–1 and a capacity retention of 94.7% at 2 A g–1 after 2000 cycles. Its remarkable properties are attributed to the hollow structure with high specific surface areas and the mesoporous structure effectively buffering the large volume change which provide additional storage sites and rapid electron/ion transfer. Cobalt doping decelerates the dissolution of Mn2+, so as to maintain good structural stability and improve the specific capacity due to the multielectron redox reaction of cobalt, as well as the carbon coating with high conductivity and thermal stability which can further inhibit the dissolution of manganese. The results indicate that the Mn–Co–O@C hybrid can be a potential cathode for AZIBs.