Fabrication of oxygen-vacancy abundant MnO2 nanowires@ NiMnxOy-δ nanosheets core-shell heterostructure for capacity supercapacitors

Structure instability and poor electrical conductivity are two major obstacles to realizing high performance of MnO2-based pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. Herein, a stable MnO2@NiMnxOy-δ core-shell heterostructure is prepared via a simple liquid-phase reaction combined with heat-treatment method, composed of ultrathin NiMnxOy-δ nanosheets with oxygen vacancies uniformly growing on the surface of ultralong MnO2 nanowires. Electrochemical test results show that the electrode exhibits a specific capacitance of 463.5 C g−1 at 1 A g−1 and has an excellent capacitance retention as high as 94.9% after 20,000 cycles. Compared with the MnO2@NiMnxOy nanowires, the introduction of oxygen vacancies in the ultrathin nanosheets of the MnO2@NiMnxOy-δ core-shell heterostructure can provide a large number of surface active sites to accelerate electron/ions transport during electrochemical reaction. Moreover, the interfacial behavior of the electrode reaction can be also adjusted due to the potential synergistic effect between one-dimensional nanowires and two-dimensional nanosheets, further the MnO2@NiMnxOy-δ core-shell heterostructure demonstrating the superior cyclic stability.