Effect of operating temperature on local structure during first discharge of 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 electrodes

The present study investigated the temperature dependence of the local structure of 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 electrodes during the first discharge cycle, using neutron and synchrotron X-ray diffraction. It was found that at 60 °C, a capacity of more than 280 mAh/g could be achieved at a voltage of 2.5-4.8 V vs. Li/Li+, which was larger than the capacity at room temperature. To clarify the reason for this, an analysis was carried out based on the pair distribution function for electrodes following their first charge and discharge cycles. The results indicated a unique distortion of Ni-O6 octahedra at higher temperature. In addition, an analysis using X-ray absorption near edge structure spectroscopy indicated a change in valence during charging and discharging based on a shift in the position of peaks associated with Mn, Ni, and Co. At 60 °C, the shift was particularly large for the Ni peak. Thus, the operating temperature can have a large effect on the behavior of especially Ni, which can influence the battery characteristics.