Voltage Decay and Capacity Loss in Lithium-Rich Manganese Oxide Cathodes: Atomic Origins, Mesoscopic Heterogeneities, and Macroscopic Evolution

Lithium-rich manganese-based oxide (LRMO) cathode materials have emerged as promising candidates for next-generation lithium-ion batteries (LIBs) due to their high specific capacity and exceptional energy density. Nevertheless, their practical application is significantly hindered by pronounced voltage decay and capacity loss during cycling, which stem from complex and interrelated mechanisms. This review presents a comprehensive, multi-scale analysis of the degradation pathways in LRMO materials, spanning from atomic-level structural dynamics to mesoscopic heterogeneities and macroscopic particle evolution. Special focus is directed toward unraveling the synergistic interplay between oxygen anionic and cationic redox processes, oxygen release, transition metal ions (TMs) migration, irreversible phase transitions, heterogeneous electrochemical reactions, and operational conditions. By integrating insights from advanced characterization, theoretical modeling, and electrochemical analyses, this review establishes a cohesive framework that elucidates the intricate relationships among oxygen activity, TMs dynamics, and structural transformations. These mechanistic insights lay a critical foundation for the development of stabilization strategies aimed at mitigating voltage decay and capacity loss. Ultimately, this review bridges the gap between fundamental mechanistic understanding and practical engineering applications, offering actionable guidance for the design of durable and high-energy-density LRMO cathode materials tailored for high-performance energy storage systems.