Comprehensive Understanding of Voltage Fade of Li & Mn Rich Cathodes

Li- and Mn-rich (LMR) cathodes have emerged as promising candidates for next-generation lithium-ion batteries (LIBs) due to their high energy density and reliance on earth-abundant elements. Unlike conventional layered transition metal (TM) oxides, LMRs utilize both TM and anion (oxygen) redox reactions to achieve superior capacity. However, their widespread commercialization is hindered by voltage fade, a persistent issue characterized by a gradual decline in the operating voltage upon cycling, which leads to significant energy density loss. This review provides a comprehensive understanding of the fundamental mechanisms contributing to voltage fade, including irreversible phase transitions, transition metal migration, oxygen loss, and microstructural degradation. Furthermore, we discuss state-of-the-art strategies for mitigating voltage fade, including elemental doping, surface coatings, composition modulation, and concentration gradient engineering. Each approach is critically evaluated in terms of its effectiveness in stabilizing the cathode structure and improving long-term electrochemical performance. By integrating recent advancements in material design, this review outlines a strategic roadmap for developing structurally robust and electrochemically stable LMR cathodes, paving the way for their practical implementation in high-energy density LIBs.