Recent advances on the manganese cobalt oxides as electrode materials for supercapacitor applications: A comprehensive review

In the past decade, the electrochemical energy storage devices have drawn great attention in many fields such as smart portable electronics and hybrid electric vehicles. Among various energy storage systems, the supercapacitors have been regarded as one of the most promising candidates owing to their high power density, long lifespan and low production cost. As known, the natural characteristics of electrode materials play an important role in determining the charge storage performance of supercapacitors. A great effort has been devoted to improving the energy density and cycling durability of supercapacitors by constructing hierarchical porous electrode materials with high specific capacity. The manganese cobalt oxides including MnCo2O4, CoMn2O4 and MnCo2O4.5 have been demonstrated to be promising battery-type electrode materials in supercapacitor application due to their high theoretical specific capacity, rich redox activity, abundant availability, and easy synthesis. However, the MnCo-oxides sometimes suffer from severe capacity deterioration due to the small specific surface area and poor electrical conductivity. In this review, the progress regarding the synthesis methods & structure control of manganese cobalt oxides-based materials has been summarized and discussed in details. The major goal of this work is to highlight the latest progress in using the existing strategies to enhance the final electrochemical performances of materials, including structural design, morphological control, and composite engineering. In addition, some potential challenges and effective strategies for the future research direction and development of manganese cobalt oxides-based electrode materials are proposed. It is believed that an in-depth understanding on the design of other transition metal oxides with ideal electrochemical properties is guided in the future.