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

Abstract

Single phases of layered LiNi 0.5Mn 0.5O 2 structure ( a=2.89 A ̊ , c=14.30 A ̊ ) with the LiNiO 2 structure and cubic Li 0.4Ni 0.3Mn 0.3O ( a=4.15 A ̊ ) with the NiO structure were synthesized by calcination of mixed oxide (NiMnO 3) and LiOH·H 2O. The optimum calcination temperatures were 1000°C in air for LiNi 0.5Mn 0.5O 2 and 700°C in nitrogen for Li 0.4Ni 0.3Mn 0.3O. To our knowledge, the Li 0.4Ni 0.3Mn 0.3O material has not been reported in the literature so far. It was converted to Li 0.7□ 0.3Ni 0.5Mn 0.5O 2 material ( a=2.89 A ̊ , c=14.34 A ̊ ) with the LiNiO 2 structure by heating at 400°C in air. Acid delithiations of LiNi 0.5Mn 0.5O 2 and Li 0.7□ 0.3Ni 0.5Mn 0.5O 2 materials were studied using a 0.5 mol dm −3 HCl solution at room temperature. The extraction reactions progressed topotactically while maintaining the crystal structures with lithium extraction of 60% in LiNi 0.5Mn 0.5O 2 and 80% in Li 0.7□ 0.3Ni 0.5Mn 0.5O 2.