科研之友
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摘要
This work reports the synthesis of the core-shell Mn3O4@NC by the controlled thermal oxidation of the MnO@NC in air. It shows that to obtain the Mn3O4@NC with a high purification, the thermal oxidation has to be done at 280 degrees C. At this temperature, MnO can be fully transformed into Mn3O4, while the combustion of the NC shell proceeds in the limited rate, allowing for the formation of the Mn3O4@NC in a limited oxidation duration. The Mn3O4@NC is found to be a promising anode material for both LIBs and SIBs. As the anode for the LIBs and SIBs, it can deliver excellent stable reversible capacities of 1220.8 and 249.5 mAh g(-1) at 100 mA g(-1), respectively. In the both cases, the Mn3O4@NC exhibits excellent rate capacities and cycling stabilities. The performance of the Mn3O4@NC for both the LIBs and SIBs is higher than that of many transition metal oxide based anodes reported. The NC shell is found to play important roles in the high performance of the Mn3O4@NC. It does not only improve the BET specific surface area and the structural stability of the Mn3O4@NC, but also increases the electric conductivity and Li/Na diffusivity of the Mn3O4@NC. The DFT calculations have demonstrated the existence of the strong electronic coupling between Mn3O4 and NC. The interface between the Mn3O4 MSs and the NC shell is suggested to be active sites for the adsorption of Li/Na ions.
