Carbon Nanotubes as electrically conducting additive for electrochemical supercapacitors based on Manganese Oxide

摘要

Nanocrystalline metal oxides can be prepared with the characteristics of large surface area, high conductivity, electrochemical stability and pseudocapacitive behaviour being able to be used as supercapacitor electrodes. Among the various metal oxides studied, amorphous and hydrated manganese oxide (a-MnO2·nH2O) is the most promising supercapacitor material due to the low cost of the raw material. In the present work, amorphous manganese dioxide (a- MnO2·nH2O) is prepared by chemical co-precipitation of Mn(VII) and Mn(II) in water medium, giving small particles of relatively high surface area. However, a-MnO2·nH2O does not afford the premise of high conductivity for being used as electrode material for supercapacitors, requiring to add a conducting agent to perform an electrode. Generally, carbon black is used as additive for electrodes due to its conductive nature and because it is chemically inert. In the present study, the use of carbon nanotubes as alternative electric conducting additive is proposed. The results obtained show that carbon nanotubes are effective in increasing the capacitance and improving the electrochemical properties of the a-MnO2·nH2O electrodes to show closer ideal capacitor behaviour when compared with carbon black. For the first time real capacitors were built from a- MnO2·nH2O/carbon nanotube composite electrodes, demonstrating high values of capacitance up to 200 F/g.