クエン酸ゲル法で合成されたLiMn₂O₄ナノ粒子の電気化学的特性

抄録

Thermal analysis, phase and electrochemical properties of nano-LiMn₂O₄ powders synthesized at low temperature by citric acid gel process were investigated. The activation energy for LiMn₂O₄ formation was 130.8kJ/mol when lithium manganese citrate was used as a precursor. The lattice parameter and volume of LiMn₂O₄ powders increased with synthesis temperature increased, which resulted from the decreased average valence of manganese. As the temperature was above 700°C, LiMn₂O₄ underwent phase transition from a cubic to a tetragonal phase, which was attributed to oxygen removal in the lattice. In cyclic voltammogram (CV) analysis, the two pairs of oxidation and reduction CV curves indicated that, apparently, the insertion and extraction reactions of lithium ion occurred in two stages. The initial discharge capacity of LiMn₂O₄ powders increased with the increasing calcination temperature, but the powders calcined at lower temperatures exhibited a better cycling behavior than the ones calcined at higher temperatures. The capacity fading of the spinel LiMn₂O₄ was due to structural damages caused by the Jahn-Teller distortion.