Journal of Power Sources, Vol.410, 38-44, 2019
Average, electronic, and local structures of LiMn2-xAlxO4 in charge-discharge process by neutron and synchrotron X-ray
The effect of Al substitution in LiMn2-xAlxO4 on the charge-discharge process was investigated by average, local, and electronic structure analyses. A Rietveld analysis of the neutron and synchrotron X-ray diffractions was performed for LiMn2O4 and LiMn1.8Al0.2O4 during the charge-discharge process. The change range of the distortion parameters, lambda and sigma(2) of the (Mn, Al)-O-6 in LiMn1.8Al0.2O4 during the charge-discharge was smaller than that of LiMn2O4. Using the Maximum Entropy Method, the covalent change between the 16d site and 32e site was mitigated by the Al substitution, which indicated stabilization of the MO6 octahedra during the charge discharge process. The PDF analysis of the neutron total scattering data was performed for LiMn2O4 and LiMn1.8Al0.2O4 before the charge-discharge. The a' of AlO6 was smaller than that of MnO6, which indicated that distortion of the MO6 octahedra was locally mitigated by the Al substitution. The distortion range of MnO6 was reduced by the Al substitution that improved the cycle performance.