title: Synthesis and Electrochemical Analyses of Manganese Oxides for Super-Capacitors.
abstract: δ-Phase and α-phase manganese oxides were prepared using a hydrothermal method and their electrochemical properties were characterized. The influence of calcination temperature on the properties of manganese oxides was studied. Crystallinities were studied by X-ray diffraction, and scanning and transmission electron microscopy were utilized to examine morphologies. Average pore sizes and specific surface areas of samples were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. After calcination in the range 300 degrees C to 600 degrees C, changes in morphology and crystallinity were observed. The flower-like shape of as synthesized samples became nanorod-like and the δ-phase changed to the α-phase. These changes may have been due to the removal of water during calcination. Furthermore, a transition stage in which the two phases coexisted was observed. Synthesized manganese oxides were mixed with carbon by sonification, to increase electric conductivity and to induce a synergistic effect between pseudo-capacitor and electric double layer capacitor (EDLC). Specific capacitances and rate durability of each composite were investigated by cyclic voltammetry in 1 M Na2SO4 electrolyte at different scan rates. MnO2 calcined at 400 degrees C exhibited the highest capacitance, probably due to its high surface area and more porous structure.
authors.forename: Taewoo
authors.initials: T
authors.lastname: Kim
authors.forename: Hyein
authors.initials: H
authors.lastname: Hwang
authors.forename: Jaeyong
authors.initials: J
authors.lastname: Jang
authors.forename: Inyeong
authors.initials: I
authors.lastname: Park
authors.forename: Sang Eun
authors.initials: SE
authors.lastname: Shim
authors.forename: Sung-Hyeon
authors.initials: SH
authors.lastname: Baeck