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MnCo₂O₄/g-C₃N₄ composite material was synthesized by the hydrothermal method, compared with MnCo₂O₄ without g-C₃N₄, it has excellent electrochemical performance. The composite material can reach a specific capacitance of 350 Fg${}^{-1}$ at 1 Ag${}^{-1}$. The capacity retention rate is 96% after 1000 cycles at the rate of 2 Ag${}^{-1}$. Experiments show that g-C₃N₄ can effectively disperse and improve the conductivity of urchin-like MnCo₂O₄, and the composite of sufficient g-C₃N₄ can give full play to the performance of urchin-like MnCo₂O₄, provide faster electronic transport channels, effectively improve the ion migration rate, and make urchin-like MnCo₂O₄ increase the rate performance under high charge and discharge rates.

In this research, manganese cobaltite (MCO) nanoparticles with different morphologies were synthesized by a simple hydrothermal method with excellent electrochemical properties. To investigate the physical features of prepared samples, XRD analysis was used to study the crystalline structure. The SEM and TEM proved that the morphology of synthesized materials formed as flake and nanoplane structures. The electrode of samples was prepared using the hydrothermal method and the electrochemical properties of samples were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cyclic stability analysis. Results showed that the flake structures of nanoparticles revealed the highest capacitance of 1971.98$\mathrm{\text{F}}\cdot {\mathrm{\text{g}}}^{-1}$ at 0.5Ag${}^{-1}$ as well as longer stability compared to the others with the nanoplane structure. The high cyclic stability of 91.47% after 5000 cycles introduces this electrode as a durable and promising electrode for use in energy storage devices.

Ultra-small MnCo₂O₄ nanocrystals/nitrogen enriched carbon nanofiber composites, with particle size as small as 2–4nm and nitrogen content as high as $\sim 11.5$at.%, were designed and used as oxygen cathode materials for Li-O₂ batteries, with an aprotic electrolyte. Via an in-situ nucleation and growth, the morphology, size and distribution of MnCo₂O₄ nanocrystals were well controlled on surface of nanofibers, with strong interfacial interactions between the two components. Benefitting from the unique microstructure and high-level nitrogen doping, the MnCo₂O₄/NCF composite can deliver discharge and charge capacities of 4147.8 and 3842.8mAh/g as oxygen cathode materials, and columbic efficiencies are about 92.6%. More importantly, the discharge products can completely decompose in charging process as evidenced by an ex-situ FESEM investigation, while for pure NCF cathode, particle and plate-like Li₂O₂ were still observed on its surface, which confirmed that the MnCo₂O₄/NCF composite has a superior electrocatalytic activity that that of NCF.