Tubules of 200 nm outer diameter spinel LiMn2O4 were prepared by thermal decomposition of an aqueous solution containing lithium nitrate and manganese nitrate at 1:2 molar ratio using a nanoporous alumina membrane as a template. After dissolving the template membrane, the resulting nanotubule array of LiMn2O4 was coated with polypyrrole to investigate the galvanostatic charge-discharge characteristics. The polypyrrole-coated LiMn2O4 tubule electrodes exhibited higher capacities than the polypyrrole-coated LiMn2O4 thin-film electrode prepared under the same conditions, except for the use of the alumina membrane; it was ca. 2.5 times greater at 0.1 mA cm-2 and became ca. 12 times greater with an increase in current density to 1.0 mA cm-2. The observed high capacity of the tubule electrode seems to have resulted from two kinds of effects: a decrease in real current density of high specific surface area at the tubule electrode and a decrease in thickness of LiMn2O4 solid phase for Li+ ions to diffuse through during the charging and discharging reactions.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry