Core-shell cathode material with size-dependent composition

A LiCoO2-based cathode material was synthesized from a core-shell structured precursor whose core was LiCoO2 and the shell was mixed metal hydroxide of MOOH (M = Ni1/2Mn1/2) co-precipitated onto the LiCoO2 seeds. The core of the final material was covered with dense [Li(Ni1/2Mn1/2)(1-X)CoXO2] shell. The core-shell cathode material showed an exceptional cycling stability at high voltage up to 4.5 V maintaining high rate performance. Further improvement up to 4.6 V was achieved applying a fluorination process. The thermal stability measurement using differential scanning calorimetry indicated that the core-shell material was more stable than conventional material having the same composition. (c) 2007 The Electrochemical Society.