A Mn/Co-oxide electrode for potential use in high energy density hybrid supercapacitors

A simple and inexpensive thermal pyrolysis method was used at the laboratory-scale to produce a high charge-storage Mn/Co-oxide electrode for hybrid supercapacitors. The material was investigated using galvanostatic charge-discharge (GCD), SEM, EDX, XPS and XRD. The Mn/Co-oxide exhibited a highly porous and intricate microstructure which allowed for high charge storage (capacitance). NaOH, LiOH, NaClO4 and LiClO4 electrolytes were employed and it was concluded that the pH, the type of anion and the size of cation played a large role in the resulting charge storage capability of the material. The highest capacitance of 4500 ± 60 mF cm−2 (1.38 mAh cm−2) was observed in 1.0 M LiOH at a current density of 0.4 mA cm−2. The high apparent capacitance was due to intercalation of cations (Na+ or Li+) into the crystalline structure of the Mn0.5Co0.5-oxide phase, rendering the electrochemical behavior of the metal-oxide closer to that of Li-ion battery electrodes than to pure supercapacitors.