Effects of manganese and cobalt on the electrochemical and thermal properties of layered Li[Ni0.52Co0.16+xMn0.32-x]O-2 cathode materials

Abstract

We investigate the effects of the Co and Mn ratio on the structure, morphology, electrochemical properties, and thermal stability of Li[Ni0.52Co0.16+xMo0.32-x]O-2 cathode materials. Li[Ni0.52Co0.16+xMn0.32-x]O-2 (x=0, 0.08, 0.16) cathode materials are prepared via high temperature calcination of LiOH and coprecipitated [Ni0.52Co0.16+xMn0.32-x](OH)(2) hydroxides. From an X-ray diffraction investigation, the prepared materials have a well ordered O-3 type alpha-NaFeO2 layer structure (R (3) over barm). As the Co content (x) is increased, the initial discharge capacity increase slightly but it is accompanied by severe capacity fading during extensive cycling. Meanwhile, a small increase of Mn enhances the electrochemical stability at high temperature (55 degrees C) as well as the thermal stability. Electrochemical impedance spectroscopy reveals that manganese substitution is effective to reduce the resistance during cycling due to stabilization of the host structure.