Oxygen Release and Its Effect on the Cycling Stability of LiNi x Mn y Co z O 2 (NMC) Cathode Materials for Li-Ion Batteries

Layered LiNixMnyCozO2 (NMC) is a widely used class of cathode materials with LiNi1/3Mn1/3Co1/3O2 (NMC111) being the most common representative. However, Ni-rich NMCs are more and more in the focus of current research due to their higher specific capacity and energy. In this work we will compare LiNi1/3Mn1/3Co1/3O2 (NMC111), LiNi0.6Mn0.2Co0.2O2 (NMC622), and LiNi0.8Mn0.1Co0.1O2 (NMC811) with respect to their cycling stability in NMC-graphite full-cells at different end-of-charge potentials. It will be shown that stable cycling is possible up to 4.4 V for NMC111 and NMC622 and only up to 4.0 V for NMC811. At higher potentials, significant capacity fading was observed, which was traced back to an increase in the…