Electrochemical Overview: A Summary of ACoxMnyNizO2 and Metal Oxides as Versatile Cathode Materials for Metal‐Ion Batteries

Abstract Early LiCoO 2 research provided the basis for the tremendous commercial success of Li + batteries since their invention in the early 1990s. Today, LiNiMnCoO 2 (Li‐NMC) is one of the most widely used batteries in the rapidly evolving electronic vehicle industry. Li‐NMC batteries continue to receive significant interest as research efforts aim to partially, or entirely, replace the use of scarcely available and toxic Co with elemental doping to form binary, ternary, and quaternary layered oxides. Furthermore, safety concerns and rising uncertainty for the future of Li supplies have resulted in growing curiosity toward non‐Li + rechargeable batteries such as Na + and K + . Unfortunately, the success of Li + host materials does not always directly transfer to Na + and K + batteries due to the difficulty of reversibly intercalating larger ions without irreparably distorting the host structure. Consequently, this report provides an overview of the Li‐based materials surrounding the success of commercial Li‐NMC and the subsequent progress of their lesser studied Na and K counterparts. The challenges for current cathode materials are highlighted, and the opportunities for progression are suggested. The summary presented in this review can be consulted to steer new and unique research avenues for layered oxide materials as metal‐ion battery cathodes.