Electrode Characteristics of Individual, MnO2 Coated Carbon Nanotubes

We investigate interfacial charge transfer between a manganese oxide (MnO 2 ) pseudocapacitor material and graphitic carbon supports in the limit where the graphitic carbon is defect free. We achieve this limit experimentally by fabricating model electrodes comprising MnO 2 deposited on single, pristine, isolated single-walled carbon nanotubes. Li ion cyclic voltammetry of the composites gives a specific capacitance in accord with MnO 2 storage capacities, but with kinetics limited by the poor electron transfer properties of defect free carbon. By fitting the data to an equivalent circuit model, we determine the charge transfer resistivity of MnO 2 -carbon interfaces to be 9 x 107 Ohm-cm when defects are absent, a limiting value for high power cathodes.