Nowadays, the energy issue has increasingly become a hot spot of social attention, and the supercapacitor as a new type of energy storage device attracts much attention due to its long service life, high power and environmental friendliness. MnO 2 based supercapacitors not only assume the characteristics of high power density, long cycle life, fast charge and discharge, but also have the advantages of low cost, broad source and environmental friendliness. Thus they have displayed a very broad application prospects and economic value in various fields. However, the specific capacitance of the MnO 2 based supercapacitor is considerably lower than the theoretical value due to its poor conductivity and limited specific surface area. Moreover, its unstable structure also results in poor cycling stability. To resolve the above mentioned problems, the current researches about the MnO 2 based supercapacitor mainly focus on finding facile and controllable preparation methods to improve the electrochemical properties like conductivity, specific capacitance, cycling stability, etc., and trying to magnify the advantages and realize synergistic effect of various electrode materials. Searching a simple and controllable electrode preparation method has become a primary task for high quality MnO 2 based supercapacitors. The common methods include sol-gel method, hydrothermal synthesis method, chemical precipitation method, low temperature solid phase method and electrochemical deposition method. The resultant powders prepared by sol-gel method have high purity, agglomerate easily due to the drying conditions. Through the chemical precipitation method can obtain uniformly distributed powders with even chemical compositions, and still, ease of agglomerat owing to high synthesis temperature. The low temperature solid phase method can efficiently overcome the shortcomings mentioned above involving the rapid growth and agglomeration of particles at high temperature, but nevertheless suffers low reaction conversion rate which is attributed to the inadequate contact among the reactants. The hydrothermal synthesis is a simple and low cost method which has been applied to prepare the powder widely at pre-sent. The powders prepared by the above methods need certain pre-treatment for the fabrication of electrode, which extends the process and is detrimental to energy saving and environmental protection. On the contrary, the electrodeposition method can directly deposit manganese dioxide on different substrates with flexible operation and controllable operating parameters. The modification of manganese dioxide electrode material has converged intensive research endeavors, the doping and composing methods are still used commonly at present, for example, a small amount of metal elements doped in manganese dioxide can improve the conductivity of the electrode, and some conductive polymers added into manganese dioxide can effectively solve the unstable structure of manganese dioxide which results in its easy dissolution in the electrolyte. In order to obtain the high-quality electrode, it is very essential to select the species of the doped materials and composited materials, their proportions, and the doping and composing methods. Now, the MnO 2 based supercapacitor is not barely composed of MnO 2 , but a combination of MnO 2 and other substances, such as a variety of carbon materials, composite materials or metal oxides. The combination of multiple composite materials can adequately make use of the characteristics of each component, which contributes to optimizing the performance of the capacitor. In addition, some scholars also found that the selection of electrolyte has great influence on expanding the electrochemical window of supercapacitors, improving the energy density and power density of capacitors. This paper briefly introduces the energy storage mechanism and summarizes the research status of capacitor electrolyte, electrode preparation and modification method. The fabrication and performance characteristics of MnO 2 based supercapacitors device are introduced, and the future research trends are also presented. © 2018, Materials Review Magazine. All right reserved.
