Electrochemical Stress at High Potential to Investigate Phase Transitions in Li[sub 1.1](Ni[sub 1/3]Mn[sub 1/3]Co[sub 1/3])[sub 0.9]O[sub 2]

The purpose of this work was to understand the long-term reversibility characteristics of by investigating the possible phase transitions of this material when subjected to high potential ( vs ) electrochemical stress. The effect on the crystal structure after first-cycle charge, extended galvanostatic cycling, and potentiostatic stress was examined by in situ X-ray synchrotron powder diffraction and ex situ X-ray powder diffraction. did not undergo any phase transition when deeply delithiated because of a lithium–nickel exchange degree of about 4% in our sample. The latter property is believed to be the reason for the improved structural stability: Nickel ions present in the interslab space keep the slabs in place, thus preventing the O3 phase from converting into the O1 phase.