Composite of Manganese Dioxide and Two-dimensional Materials Applied to Supercapacitors

The world is currently facing a series of energy-related problems and challenges.In response, scientists are committed to seeking green high-performance energy storage devices to meet the demands of long-term, sustainable, and innovative development in the future.As a new type of green energy storage device, the supercapacitor has the advantages of high power density, high theoretical specific capacitance, fast charge and discharge speed, long cycle life, high safety, environmental friendliness, and economy to help people cope with the energy crisis.In addition, energy storage devices including Li-ion batteries and supercapacitors are being transformed from heavy, rigid, and bulky devices into light, flexible, and small units to fulfill the needs of the next generation.Among these energy storage systems, the electrode material is an important factor affecting the performance of supercapacitors.In recent years, supercapacitors based on manganese dioxide have been widely studied owing to their high theoretical specific capacitance, good chemical stability, and environmental friendliness.At the same time, a variety of two-dimensional materials are also used as supercapacitor electrode materials after graphene.Two-dimensional structural features play an important role in improving the energy density of electric double-layer capacitors and improving the pseudocapacitance of capacitors.To achieve high specific capacitance and high rate of performance, combining manganese dioxide with two-dimensional materials is a promising option.In this paper, we systematically introduce the application of composites that combine twodimensional materials represented by graphene and manganese dioxide in supercapacitors, and considers the electrochemical properties of these composites.However, there is still a long way to go in order to fabricate a suitable hierarchical structure consisting of two-dimensional materials and manganese dioxide.For example, a suitable twodimensional material must be chosen and combined with manganese dioxide to form composites that possess excellent electrochemical properties.In addition, the fabrication methods for these composites are a principal factor that affects their performance.Thus, there are reasons for us to strongly believe that if these key issues are resolved, the properties of these composites consisting of manganese dioxide and two-dimensional materials will make great progress.Overall, this paper only points out some general directions for these kinds of composites in the future, such as principles for choosing the two-dimensional materials to combine with manganese dioxide, and the composite methods which have been reported previously.We are pleased that other researchers are being inspired by our work, and we are looking forward to seeing better studies in this field.