Study on Supercapacity Properties of Manganese Dioxide Active Material by the Cation Concentration Change on the Electrode Surface

Abstract

A four-electrode system was developed to measure in-situ the cation concentration change on the supercapacitor electrode surface for the first time during the charge/discharge process. While the MnO2 electrode was used in a supercapacitor in K2SO4 solution, the potassium ion concentration on the electrode surface was reversible change during the charging/discharging process, decreasing with the reduction process and increasing with the oxidation process. It is clearly clarified that the charge storage mechanism of manganese dioxide, as a supercapacitor active material, involves a fast redox reaction through reversible insertion/desertion of potassium ion and variation of manganese valance.