Effects of manganese and cobalt on the electrochemical and thermal properties of layered Li[Ni_(0.52)Co_(0.16+x)Mn_(0.32-x)]O_2 cathode materials

摘要

We investigate the effects of the Co and Mn ratio on the structure, morphology, electrochemical properties, and thermal stability of Li[Ni_(0.52)Co_(0.16+x)Mn_(0.32-x)]O_2 cathode materials. Li[Ni_(0.52)Co_(0.16-x)Mn_(0.32-x)]O_2 (x=0, 0.08, 0.16) cathode materials are prepared via high temperature calcination of LiOH and copre-cipitated [Ni_(0.52)Co_(0.16+x)Mn_(0.32-x)](OH)_2 hydroxides. From an X-ray diffraction investigation, the prepared materials have a well ordered O_3 type a-NaFeO_2 layer structure (R3m). 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 ℃) 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.