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

Novelhollow Mn-Co-O@C yolk-shell microsphereswith carbon shells were fabricated from the self-assembled sustainableMn-Co-MOF. Manganese-based cathodes are promising candidates foraqueous zinc-ionbatteries (AZIBs) due to their high-voltage platform, low-price, environmentalfriendliness, 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 leadto unsatisfactory rate performance and fast capacity decay. HollowMn-Co-O@C yolk-shell microspheres with carbonshells were fabricated from self-assembled Mn-Co-metal-organicframeworks via combining facile normal temperature and annealing methods.Mn-Co-O@C achieved an excellent specific capacity of401 mA h g(-1) and a capacity retention of 94.7% at2 A g(-1) after 2000 cycles. Its remarkable propertiesare attributed to the hollow structure with high specific surfaceareas and the mesoporous structure effectively buffering the largevolume change which provide additional storage sites and rapid electron/iontransfer. Cobalt doping decelerates the dissolution of Mn2+, so as to maintain good structural stability and improve the specificcapacity due to the multielectron redox reaction of cobalt, as wellas the carbon coating with high conductivity and thermal stabilitywhich can further inhibit the dissolution of manganese. The resultsindicate that the Mn-Co-O@C hybrid can be a potentialcathode for AZIBs.

Automated summary

Novelhollow Mn-Co-O@C yolk-shell microspheres with carbon shells were synthesized from self-assembled Mn-Co-MOF. The hollow structure with high specific surface areas and mesoporous structure effectively buffered the large volume change, providing additional storage sites and rapid electron/ion transfer. Cobalt doping decelerated the dissolution of Mn2+, maintained good structural stability, and improved the specific capacity due to the multielectron redox reaction of cobalt. The carbon coating further inhibited the dissolution of manganese and exhibited high conductivity and thermal stability. The Mn-Co-O@C hybrid showed promising potential as a cathode material for AZIBs, achieving an excellent specific capacity and capacity retention after cycling.