Effect of precursor structure transformation on synthesis and performance of LiNi0.5Co0.2Mn0.3O2 cathode material

The precursor has great influences on electrochemical performance of LiNi1-x-yCoxMnyO2 cathode materials. However, the effect of precursor structure transformation on the synthesis and electrochemical performance of LiNi1-x-yCoxMnyO2 is rarely mentioned. In this paper, Ni0.5Co0.2Mn0.3(OH)2 and different-temperature-preheated Ni0.5Co0.2Mn0.3(OH)2 were synthesized to prepare LiNi0.5Co0.2Mn0.3O2. The results show that Ni0.5Co0.2Mn0.3(OH)2 precursor transform into spinel-type solid solution (Ni0.5Co0.2Mn0.3)3O4 after preheating, and the contents of Ni3+, Co3+ and Mn4+ increase significantly. Comparative analyses reveal that the precursor structure change has no obvious effects on the crystal structure and surface morphology of the prepared LiNi0.5Co0.2Mn0.3O2. But the preheated precursors can reduce the undesirable lithium loss due to lithium volatilization in the high-temperature sintering process, leading to excess lithium ions enter into transition metal ions layer. Lithium excess can affect the amount of Ni3+, lattice parameters and residual lithium compounds on the particle surface, which in turn lead to different electrochemical behaviors of the prepared LiNi0.5Co0.2Mn0.3O2.