Correlating the phase evolution and anionic redox in Co-Free Ni-Rich layered oxide cathodes

摘要

Current trend of high-capacity Ni-rich layered cathode is to develop high-Ni and low-Co or Co-free oxides.The high Ni content layered oxides provide great advantages in capacity,cost and environmental benignity,similar to LiNiO_2 parent compound.But they also inherit drawbacks in structural and chemical instability at high voltages upon cycling.Elemental substitution plays a profound role in addressing these challenges.This work elucidates the roles of Al doping in cationic redox and anionic oxygen activity in LiAl_xNi_(1-x)O_2 using combined X-ray absorption spectroscopy (XAS),resonant inelastic X-ray scattering (RIXS) as well as operando differential electrochemical mass spectrometry (DEMS).Using synchrotron wide-angle X-ray scattering (WAXS),we extrapolate a general principle of phase transition and its coupling with lattice anionic oxygen redox.These findings shed light on the advancement of high-capacity,stable-cycling and safe-operating Ni-rich cathode materials for next generation Li-ion batteries.