Cation-disordered metal oxides as cathode materials for Li ion batteries have been overlooked from early studies due to to the restriction of Li ion diffusion, leading to poor electrochemical performance. However, the discovery of a new disordered rocksalt (DRX) structured material Li1.211Mo0.467Cr0.3O2 with a high capacity of >260 mAh g−1 at 0.05 C opened new research prospects in this emerging field and established DRX materials as a promising alternative with wider choices of transition metal elements compared with currently widely used layered cathode materials. Some of the major obstacles of the DRX materials include γ-LiFeO2 type cation short-range-order that impedes Li ion diffusion, irreversible oxygen loss, and transition metal dissolution, which also present challenges for appropriate characterization techniques. Several performance optimization strategies have been employed, including fluorine incorporation, high entropy modification, and surface coating. This review article focuses on advancements in characterization techniques to uncover underlying mechanisms of Li ion diffusion and degradation of the DRX cathode materials to address the abovementioned challenges and provide inspiration for future studies of this class of materials.