Influence of Mn content on the morphology and electrochemical performance of LiNi1−x−yCoxMnyO2 cathode materials

Abstract

LiNi_1−x−yCo_xMn_yO₂ cathode materials were successfully synthesized by a sol–gel method. X-Ray diffraction patterns show that these materials have a typical layered structure with Rm space group. The effect of Mn content and sintering temperature on the surface morphology has been carefully examined by scanning electron microscopy. Among the substituted materials synthesized, LiNi_0.65Co_0.25Mn_0.1O₂ sintered at 850 °C has shown the best characteristics in terms of initial capacity (198 mA h g⁻¹) and capacity retention (92%). However, excessive Mn substitution (y > 0.3) leads to a significant decrease in both initial capacity and capacity retention. Preliminary X-ray absorption near edge structure (XANES) results for LiNi_1−x−yCo_xMn_yO₂ cathode materials revealed that the oxidation state of Ni is decreased when the amount of Mn substituted for Ni is increased.