Progress on Failure Mechanisms and Modification Strategies of Ni‐Rich Ternary Cathode Materials

Ni‐rich ternary cathode materials deliver high reversible capacity and energy density, making them leading candidates for next‐generation high‐energy‐density lithium‐ion batteries. However, increasing Ni content inevitably destabilizes the layered structure, accelerates interfacial side reactions, and induces mechanical degradation, creating a trade‐off between capacity and longevity. This review provides a comprehensive analysis of the coupled failure mechanisms that underlie this trade‐off. Cation mixing and lattice oxygen release are identified as primary triggers that initiate irreversible phase transitions and surface reconstruction, which in turn promote microcracking and electrolyte infiltration, establishing a self‐amplifying degradation loop that accelerates capacity fading. Based on this mechanistic understanding, recent advances in modification strategies are critically examined, including elemental doping, surface coating, concentration‐gradient design, single‐crystal engineering, defect regulation, and morphology optimization. The review highlights a paradigm shift from isolated modifications toward synergistic, multiscale design that integrates bulk structural stabilization, surface and interfacial protection, and particle mechanical integrity. Finally, future directions are proposed, emphasizing the extension of these synergistic design principles to all‐solid‐state battery systems, where solid–solid interfacial compatibility poses new challenges and opportunities.