Study On Manganese Dioxide As Electrode Materials For Supercapacitor

Manganese oxide(MnO2)with advantages such as natural abundance,low cost and high theoretical capacitance(1370 F/g)is considered as one of the most promising electrode materials for pseudocapacitors,but the stablity and electrochemical properties of MnO2 materials always become poor,which due to the collapse of crystal structure during electrochemical reactions.Furthermore,the intrinsically poor electrical conductivity of MnO2 is a hindrance to obtain high theoretical electrochemical performance in practical application.It is the aim of this work to enhance the electrochemical performance of MnO2.To improve the stablity and electrical conductivity of MnO2-based electrodes by nanocrystallization and doping.The main contents of this paper are as follows.1?Nanorods MnO2 was synthesized by a hydrothermal method,compared with the coprecipitation synthesis of MnO2,Nanorods MnO2 with high specific surface area can offer more active electrochemical reaction site and short transport/diffusion distance for electrolyte ions diffusion.The electrochemical test result suggested that the specific capacitance of Nanorods MnO2 was 134.7 F/g,which is higher than the coprecipitation synthesis of MnO2,the power performance improved obviously,the electrochemical impedance of Nanorods MnO2 was decreased,which promotes the conductivity of Nanorods MnO2.2?Bi-doped MnO2 has been prepared by a hydrothermal method.The crystal structure and morphological properties of Bi-doped MnO2 have been characterized by XRD,XPS,SEM,HRTEM and the electrochemical performances have been also tested.The XRD and HRTEM results suggest that Bi-doped MnO2 is ?-MnO2 and the bismuth element is successfully doped into the crystal lattice of ?-MnO2.The electrochemical performances of Bi-doped MnO2 are notably improved compared with ?-MnO2.The specific capacitance of Bi-doped ?-MnO2 electrode materials is 265 F/g at a current density of 1 A/g,which is 1.05 times higher than that of pure ?-MnO2(129 F/g)synthesized under the same situation.The result of EIS shows that doping Bi has reduced the charge transfer resistance of ?-MnO2 and enhanced conductivity.the capacitance of Bi-doped ?-MnO2 is kept at of 95% of the initial capacitance after 2000 cycles,higher that the pure ?-MnO2 synthesized under the same situation.Therefore,Doping Bi is helpful to improve the performance of ?-MnO2 as electrode materials for supercapacitor...