Abstract

The Li[Li0.23Co0.3Mn0.47]O2 cathode material was prepared by a sol−gel method. Combinative X-ray diffraction (XRD) and Raman scattering studies showed that the material was a solid solution rather than a composite of nano Li2MnO3 and LiCoO2. The material had a high discharge capacity of 250 mAh g−1 in the voltage window of 2.0−4.8 V. However, the capacity retention was poor. The material showed different electrochemical mechanisms in the first charge and subsequent cycles. Galvanostatic intermittent titration technique (GITT) study showed that the Li+ diffusion coefficients during the first charge were as small as 10−19 cm2 s−1 because of the high kinetic barriers associated with the concurrent Li+ extraction, oxygen loss, and structural rearrangement. The Li+ diffusion coefficients increased to 10−14 cm2 s−1 after the first charge. However, they were still much smaller than those of typical layered materials such as LiCoO2 and Li(Ni1/3Co1/3Mn1/3)O2. Electrochemical impedance spectroscopy (EIS) study showed that the large interface impedance at high potential seriously hindered the electrode performance of the material. A lower charge cutoff voltage of 4.6 V was the most suitable for this material considering that the correponding reversible capacity (∼200 mAh g−1) was attractive for high energy density lithium ion batteries.