as 4.7 V-class cathode materials were prepared with our self-reaction method at 650, 700, and 750°C calcination temperatures respectively, and their electrochemical properties and crystal structures were studied. The sample at 700°C was assigned to the space group in the X-ray diffraction analysis. On the contrary, the space group of the sample calcined at 650 or 750°C fell into because diffraction peaks from were missing. The sample at 700°C showed a one-step profile in the charge/discharge curve and this contrasted with the other samples showing two-step ones. In spite of their different structures, these three samples had the same initial capacities of about 123 mAh/g. They gave similarly good cycle performance as well, but the sample at 650 or 750°C maintained a little higher capacity after 50 cycles of charge/discharge than the sample at 700°C. From the analysis of transformation of the crystal structure of during charging, it was found that underwent the electrochemical reactions at three stages unlike with two stages.
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Takahashi et al. (2003) studied this question.