  Li-ion batteries (LIBs) are the most widely used form of energy storage in
mobile electronic devices and electric vehicles. Li-ion battery cathodes with
the composition LiNixMnyCozO2 (NCMs) currently display some of the most
promising electrochemical characteristics for high performance LIBs. NCM
compositions with high nickel content (x > 0.8) exhibit the largest specific
capacity while undergoing fast degradation and presenting safety issues. As the
main degradation mechanisms of NCM materials and the mitigation of their
degradation, are still subjects of many ongoing studies, this work summarizes
the current knowledge on the subject. Here, the existing literature is reviewed
to present the structural and electrochemical degradation of NCM with varying
Ni stoichiometries (NCM111, NCM622, NCM811, and beyond). Routes for hindering
the degradation of NCM are discussed as a function of Ni content in NCM and
include doping, application of protective coatings, and engineering of the
microstructure. A comprehensive understanding of the main degradation pathways
of NCM is key to applying the most appropriate mitigation strategies and keep
advancing towards higher energy NCM materials with longer cycle-life.
