Synthesis and characterization of nano-LiMn₂O₄ powder by tartaric acid gel process

Polycrystalline nano-LiMn₂O₄ spinel powder was synthesized by the tartaric acid gel process and developed without any detectable minor phase at 300°C. The powders synthesized by the tartaric acid gel process had a relatively smaller particle size, larger specific surface area and narrower particle size distribution than those prepared by the conventional solid state reaction. The average valence of manganese decreased with increasing synthesis temperature and resulted in an increase of the lattice parameter with calcination temperatures. As temperatures were increased to above 500 °C, LiMn₂O₄ underwent phase transition from a cubic to a tetragonal phase by removing oxygen ion in the lattice. From the results of MAS NMR, LiMn₂O₄ spinels formed at 300-800°C had a large Knight shift of ∼520 and 560 ppm in reference to LiCl.