Synthesis and Characterization of Carbon-Coated LiNi_1/3Co_1/3Mn_1/3O₂ in a Single Step by an Inverse Microemulsion Route

Layered LiNi(1/3)Co(1/3)Mn(1/3)O2, which is isostructural to LiCoO2, is considered as a potential cathode material. A layer of carbon coated on the particles improves the electrode performance, which is attributed to an increase of the grain connectivity and also to protection of metal oxide from chemical reaction. The present work involves in situ synthesis of carbon-coated submicrometer-sized particles of LiNi(1/3)Co(1/3)Mn(1/3)O2 in an inverse microemulsion medium in the presence of glucose. The precursor obtained from the reaction is heated in air at 900 degrees C for 6 h to get crystalline LiNi(1/3)Co(1/3)Mn(1/3)O2. The carbon coating is found to impart porosity as well as higher surface area in relation to bare samples of the compound. The electrochemical characterization studies provide that carbon-coated LiNi(1/3)Co(1/3)Mn(1/3)O2 samples exhibit improved rate capability and cycling performance. The carbon coatings are shown to suppress the capacity fade, which is normally observed for the bare compound. Impedance spectroscopy data provide additional evidence for the beneficial effect of a carbon coating on LiNi(1/3)Co(1/3)Mn(1/3)O2 particles.