Synthesis and Electrochemical Properties of Li[Ni1/3Co1/3Mn(1/3-x)Mgx]O2-yFy

초록

Recently, it has been investigated the high power characteristics of Li[Ni1/3Co1/3Mn1/3]O2 materials as well as its thermal stability for HEV application. However, Li[Ni1/3Co1/3Mn1/3]O2 is known to have unstable cycling performance and their capacity fades especially when charged and discharge at high voltage and high temperature. Ideally, Li[Ni1/3Co1/3Mn1/3]O2 consists of Ni2+, Co3+, and Mn4+ in formal charges, and the solid-state redox reactions of Li[Ni1/3Co1/3Mn1/3]O2 is shown that tetravalent manganese ions are not participated in the redox reaction. A possible modifications to improve electrochemical performances is to substitute metal ions for Ni, Co, Mn for stabilization of the layered structure upon cycling. Good electrochemical properties were shown for the Mg doped materials such as LiMgxCo1-xO2 and LiMgxNi1-xO2, because the Mg2+ ions do not participate in the redox process so that the stabilization of the host structure was achieved. Subsequently, this resulted in the enhanced cycling stability, accompanied by the suppression of the decomposition reaction at high cut-off charged state. Furthermore, oxygen replacement by F seemed to be substantially effective for the achievement of structural stability in spinel LiAl0.2Mn1.8O4, as reported by Amatucci et al.. Therefore, the aim of the present work is to investigate the effects on the structural stability and electrochemical behavior of Mg and F doped Li[Ni1/3Co1/3Mn1/3]O2.