Electrochemical and structural properties of Li-rich layered Li1.2Ni0.2Mn0.6O2 cathode materials have been investigated by measurements of rate capability, chemical diffusion coefficient of Li+, synchrotron X-ray diffraction, and neutron diffraction. Faster initial charging enhanced the rate capability and the chemical diffusion of Li+ in solid. In the X-ray and the neutron diffraction patterns, the peaks related to the distance of interlayer, such as (003) and (108) in the rhombohedral R (3) over barm notation, broadened upon charging. Furthermore, increasing the initial charging rate decreased this broadening of the peaks. These results indicate that structural stabilization plays an important role in diffusion of Li+ in Li1.2Ni0.2Mn0.6O2, and leads to the high rate capability. (C) 2015 Elsevier Ltd. All rights reserved.