Electrochemical Activation of Oxygen Vacancy-Rich Nitrogen-Doped Manganese Carbonate Microspheres for High-Performance Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) are considered as one of the ideal devices for large-scale energy storage because of their safety, low cost, and nontoxicity. Unfortunately, the choice of cathode materials for ZIBs is still limited. Herein, a novel oxygen vacancy-rich nitrogen-doped MnCO 3 (MnCO 3 @N) microsphere is reported as a cathode material for rechargeable ZIBs, which displays a relatively high reversible capacity of 171.6 mAh g -1 at 100 mA g -1 , outstanding rate performance, and long-term cyclic stability up to 1000 cycles at 1000 mA g -1 . The better electrochemical performances of MnCO 3 @N should be attributed to the introduction of oxygen vacancies in the MnCO 3 microcrystal by nitrogen doping, which not only improves the conductivity of MnCO 3 microspheres but also creates more active sites for zinc-ion diffusion. In addition, the energy storage mechanism of the MnCO 3 @N microspheres is systematically investigated. During the initial charge process, the MnCO 3 @N microspheres are activated to form MnO@N due to the insertion of Zn 2+ , and partial MnO@N is further oxidized into layered-type MnO 2 @N, which becomes a part of the active material for subsequent energy storage. This work not only provides a new insight for the ZIB cathode but also deepens the understanding of the energy storage mechanism of carbonate materials.