Electrochemical cycling effect on structural parameters and electron density of Li1−xNi0.5Mn1.5O4 using synchrotron X-ray analyses

We investigated the electrochemical cycling effects on the average, local, and electronic structures of 1st and 28th cycled Li1−xNi0.5Mn1.5O4 (LNMO) by Rietveld refinements, the maximum entropy method (MEM) for synchrotron X-ray, and X-ray absorption spectroscopy (XAS) using unexposed cathode materials. The results obtained with Rietveld refinements and XAS showed that the electrochemical cycling increases the transition metal valences, distorts the (Ni, Mn)-O6 octahedral, and decreases the Ni content in LNMO. Through MEM analyses we found that Li ions were stabilized by the electrochemical cycling. We also used synchrotron X-ray analyses to ascertain the correlation among specific capacity degradation, average and local structures, and the electron density before and after cycled LNMO.