Manganese oxides (MnO2) have particularly received increasing attention owing to their high theoretical specific capacitance of 1370 F/g, low-cost, natural abundance, and environmental benignity. However, MnO2 suffers from low electrical conductivity (10−5 to 10−6 S/cm), low ionic diffusion constant (~10−13 cm2/V s), and low structural stability, which results in low electrochemical utilization and poor cycling life. It is therefore important to explore new strategies to improve the electrochemical performance of MnO2. The effective methods to maximize the performance involve (i) reducing MnO2 structures to a nanoscale range and (ii) compositing MnO2 with highly conductive materials. In this chapter, we will first introduce the rapid development of MnO2 nanostructures for supercapacitors. Then the fundamental charge storage mechanism of MnO2 will be specifically clarified. The preparation methods of MnO2 nanostructures and their composites will be subsequently summarized. Then, we will pay great attention to the most recent development of MnO2-based nanostructures for supercapacitors, which is the main body of this chapter. The practical application of MnO2 nanostructures for symmetric and asymmetric supercapacitors will be discussed. Finally, we will present a brief perspective regarding the rational design and synthesis of MnO2-based nanostructures.
Part of the book: Supercapacitor Design and Applications