Study of Overcharge Behavior of Li1+x(Ni1/3Mn1/3Co1/3)1-xO2 Using In Situ and Ex Situ X-ray Synchrotron Diffraction

Structural investigation was performed on a range of NMC materials, Li 1+x (Ni 1/3 Mn 1/3 Co 1/3 ) 1-x O 2 (0≤ x ≤ 0.13), using in situ X-ray synchrotron diffraction while electrochemically cycling them between 2.5 and 5.0 V vs. Li/Li + . From the analysis of the obtained data, an irreversible phase transformation of part of the starting O3 phase ( R 3 − m ) to the O1 phase ( P 3 − m 1) was observed for all the NMC samples, where the O1 phase was detected at more negative potentials with increasing overlithiation content. Moreover a second irreversible reaction was detected at positive potentials using ex situ X-ray synchrotron diffraction for overlithiated NMC (x = 0.1) that involved loss of Li 2 MnO 3 ordering in the structure.