Synthesis and characterization of lithium nickel manganese oxides and their delithiated phases

Single phases of layered LiNi0.5Mn0.5O2 structure (a=2.89 ?, c=14.30 ?) with the LiNiO2 structure and cubic Li0.4Ni0.3Mn0.3O (a=4.15 ?) with the NiO structure were synthesized by calcination of mixed oxide (NiMnO3) and LiOH·H2O. The optimum calcination temperatures were 1000°C in air for LiNi0.5Mn0.5O2 and 700°C in nitrogen for Li0.4Ni0.3Mn0.3O. To our knowledge, the Li0.4Ni0.3Mn0.3O material has not been reported in the literature so far. It was converted to Li0.70.3Ni0.5Mn0.5O2 material (a=2.89 ?, c=14.34 ?) with the LiNiO2 structure by heating at 400°C in air. Acid delithiations of LiNi0.5Mn0.5O2 and Li0.70.3Ni0.5Mn0.5O2 materials were studied using a 0.5 moldm-3 HCl solution at room temperature. The extraction reactions progressed topotactically while maintaining the crystal structures with lithium extraction of 60% in LiNi0.5Mn0.5O2 and 80% in Li0.70.3Ni0.5Mn0.5O2.