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Manganese-based oxides are one of the most promising high-performance supercapacitor (SC) electrode materials. In this work, a stable MnOx nanowires@MnOx nanosheets core–shell heterostructure electrode material consisting of MnOx nanosheets grown uniformly on the surface of MnOx nanowires has been prepared by a simple liquid phase method followed by thermal treatment. The electrode displays a specific capacity of 336 F g − 1 at 1 A g − 1 and exhibits a good cycling life of 83% capacitance retention after 5000 cycles. This is mainly due to the synergy effect between the one-dimensional MnOx nanowires as the backbone structure and the two-dimensional MnOx nanosheets with large specific surface area provide more active sites and the rapid transmission of electrons. In this work, a stable MnOx nanowires@MnOx nanosheets core–shell heterostructure electrode materials consisting of vertical MnOx nanosheets grown evenly on the surface of MnOx nanowires by a simple liquid phase method followed by thermal treatment was successfully synthesized. Moreover, the synergy effect between one-dimensional MnOx nanowire as a backbone structure and two-dimensional MnOx nanosheet with electrochemical active sites reveals good performance. [ABSTRACT FROM AUTHOR]

Due to the high energy density and low cost, LiNi1/3Co1/3Mn1/3O2 is wildly explored as a promising cathode material for lithium-ion batteries. However, this material suffers from the destruction of surface structure in the electrolyte and the reacting of electrode with the electrolyte during cycles in highly voltage. Herein, we rationally designed core-shell nanostructure LiNi1/3Mn1/3Co1/3O2@ ultrathin δ-MnO2 nanoflakes cathode material with excellent capacity retention and rate capacity by a liquid-phase precipitation method. The unique ultrathin δ-MnO2 nanoflakes shell nanostructure plays a key role in effectively improving rate performance and cycle life of LiNi1/3Co1/3Mn1/3O2. The electrode with the coating amount of 3 wt% exhibits excellent cycle performance and superior rate capacity compared with bare electrode. The δ-MnO2 nanoflakes-coated layer can react with Li+ during cycling and convert to spinel phase, resulting in a reversibly de/lithiation coating layer to improve its specific capacity compared with other inactive coating layer, and the spinel phase can also provide a three-dimensional lithium ions diffusion channels and thus promote lithium ions diffusion. Judging from the discussion, it can be concluded that the role of δ-MnO2-nanoflakes coating layer not only acts as a protective layer to impede the electrode directly contact with electrolyte but also accelerates lithium ions diffusion and improve its specific capacity. [ABSTRACT FROM AUTHOR]

Here, we proposed a rational design of a plumage-like MnO2@NiCo2O4 core-shell architecture by a mild hydrothermal and chemical bath deposition method. The hierarchical structure comprises the stable “scaffold” of the MnO2 nanowires and the high-activity “fluff” of ultrathin NiCo2O4 nanosheets. Besides, considering the cost of nickel and cobalt elements, the content of NiCo2O4 was controlled within 50% in our design. The ideal MnO2@NiCo2O4-8h electrode achieved remarkable electrochemical performances with high specific capacity of 618.0 C g−1 at 1 A g−1, outstanding rate capability of 89% from 1 to 10 A g−1, and superior cycling stability of 71% after 5000 cycles. Furthermore, the synergy capacitance was also evaluated to be 360.7 C g−1 with a synergy efficiency of 58%. The smart design is suitable for constructing advanced electrode material for high-performance supercapacitor. [ABSTRACT FROM AUTHOR]

A stable MnO x @C@MnO x core-shell heterostructure consisting of vertical MnO x nanosheets grown evenly on the surface of the MnO x @carbon nanowires are obtained by simple liquid phase method combined with thermal treatment. The hierarchical MnO x @C@MnO x heterostructure electrode possesses a high specific capacitance of 350 F g -1 and an excellent cycle performance owing to the existence of the pore structure among the ultrasmall MnO x nanoparticles and the rapid transmission of electrons between the active material and carbon coating layer. Particularly, according to the in situ Raman spectra analysis, no characteristic peaks corresponding to MnOOH are found during charging/discharging, indicating that pseudocapacitive behavior of the MnO x electrode have no relevance to the intercalation/deintercalation of protons (H + ) in the electrolyte. Further combining in situ X-ray powder diffraction analysis, the diffraction peak of α-MnO 2 can be detected in the process of charging, while Mn 3 O 4 phase is found in discharge products. Therefore, these results demonstrate that the MnO x undergoes a reversible phase transformation reaction of Mn 3 O 4 ↔α-MnO 2 . Moreover, the assembled all-solid-state asymmetric supercapacitor with a MnO x @C@MnO x electrode delivers a high energy density of 23 Wh kg -1 , an acceptable power density of 2500 W kg -1 , and an excellent cyclic stability performance of 94% after 2000 cycles, showing the potential for practical application., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)