Voltage Decay in Li‐Rich Layered Oxide Cathodes: From Multiscale Mechanism Clarification to Integrated Strategies Design

Lithium‐rich layered oxides (LLOs) are recognized as promising next‐generation cathodes for their high specific capacity and low cost. However, a severe voltage decay issue during long‐term cycling decreases the exceptional energy density, presenting a critical challenge for their application. This review systematically discusses the voltage decay mechanism in LLOs, progressing from intrinsic characteristic descriptions to a comprehensive mechanical interpretation of interrelated multiscale processes: microscale erosion (irreversible lattice oxygen reaction and transition metal ions migration), mesoscale degeneration (phase transformation from layer to spinel or rock‐salt structure), and macroscale failure (the propagation of microcracks). Collectively, these multi‐scale processes induce the coupled decline of the discharge voltage plateau from both thermodynamic and kinetic perspectives. Following a detailed discussion of the underlying mechanism, this review summarizes recent advances in mitigating the voltage decay through the integrated internal‐external design strategy. Finally, future research directions are proposed, including elucidating the voltage decay mechanism from a panoramic view and developing tailored strategies for stabilizing the bulk and interfacial structures of LLOs. This review aims to clarify the persistent ambiguity surrounding voltage decay in LLOs, fully exploit the electrochemical advantages of these anion redox‐based cathodes, and accelerate the development of high‐energy‐density lithium‐ion batteries.