MnO2-graphene based composites for supercapacitors: Synthesis, performance and prospects

Supercapacitors stand out among some traditional energy storage devices due to their advantages such as long cycle stability, fast charge-discharge performance and high-power density. Therefore, it is necessary to explore high-performance electrode materials for application in supercapacitors. Manganese dioxide (MnO2) has high theoretical capacitance and high energy density, however, the deterioration of volume expansion and low conductivity directly affect its wide application. Graphene has attracted great interest owing to its invention. The combination of graphene and MnO2 can not only highlight the low resistance, large specific surface area and thermal stability of graphene, but also solve the shortcomings of MnO2 alone as an electrode material. The proposal of composite materials has also promoted the development and application of electrode materials in supercapacitors. Hence, this review aims to summarize the synthetic strategies and research progress of MnO2-graphene based multi-element composites, including the combination of MnO2-graphene with various carbon materials, transition metal oxides and conducting polymers, respectively. Finally, the possible development directions of MnO2-graphene based composite electrode materials in the future are also prospected.