Nanocrystalline orthorhombic LiMnO2 cathode materials synthesized by a two-step liquid-phase thermal process

Orthorhombic LiMnO2 (o-LiMnO2) particles of nano-sized grain were successfully synthesized using a two-step liquid phase thermal process at low temperature. Trimanganese tetraoxide (Mn3O4) particles as a precursor for o-LiMnO2 were prepared via a solvothermal route, in which potassium permanganate (KMnO4) powder was reduced with a primary alcohol, e.g., CH3OH or CH3CH2OH. And a hydrothermal process in lithium hydroxide aqueous solution at 160–180 °C was utilized to transform Mn3O4 particles to nanocrystalline o-LiMnO2. The electrochemical characterization of as-synthesized o-LiMnO2 particles as cathode materials for assembled Li/o-LiMnO2 cells by cycling galvanostatically in the voltage range of 2.0–4.3 V vs. Li+/Li at a current density of 20 mA g−1 at room temperature, indicated that the initial specific capacity was about 225 mA h g−1 and the specific capacity increased to 232 mA h g−1 after several cycling. A coulombic efficiency of more than 95% was achieved, and the discharge capacity of over 30 cycles could be more than 182 mA h g−1. The electrochemical capacity and its retention behavior improved presumably due to smaller particle size and high crystallinity, and thus suggested that as-developed two-step liquid phase thermal process could be a promising method for readily synthesizing highly ordered o-LiMnO2 phase of good electrochemical performances.