Structural change of LiNi1/2Mn1/2O2 during charge and discharge in nonaqueous lithium cells

The structural change of LiNi1/2Mn1/2O2 (a=2.89 Å, c=14.31 Å in hexagonal setting) during charge and discharge was examined by means of ex-situ X-ray diffraction (XRD) measurements. The integrated intensity ratio of the (0 0 3) to (1 0 4) diffraction lines increased from ca. 0.9 at an initial state to ca. 1.5 when LiNi1/2Mn1/2O2 was oxidized up to x=0.7 in Li1−xNi1/2Mn1/2O2 corresponding to the charge capacity of 200 mA h g−1 based on the sample weight, while the change in lattice dimensions of a- and c- axis was similar to those of LiCoxNi1−xO2. The change in the intensity ratio of I(0 0 3)/I(1 0 4) was reversible between ca. 0.9 and 1.5 during charge and discharge. From these results, structural changes of layered lithium insertion material of LiNi1/2Mn1/2O2 during charge and discharge were discussed.