Controlled Cooling‐Induced Modulation of Transition Metal‐Oxygen Covalency for Mitigating Electrochemical Performance Degradation in Lithium‐ and Manganese‐Rich Layered Oxide Cathodes

Practical application of Li‐rich and Mn‐rich cathodes has been hampered, despite their high theoretical capacity, owing to severe degradation of electrochemical performance accompanied by pronounced voltage decay. Herein, we modulate covalency between transition metals and oxygen to retard crystal structural and electrochemical degradation. Moderate covalency delocalizes electrons within the crystal structure, leading to a more ordered layered structure with reduced interplanar strain. In contrast, relatively weak covalency results in less layered ordering accompanied by highly localized strain. The localized strain facilitates transition metal migration to form an antiphase boundary, diamond‐patterned Li/transition metal ordering, and a rock‐salt‐like phase. Our results elucidate the relationship among the transition metal–oxygen covalency, interplanar lattice strain, transition metal migrations, and the degradation behavior of crystal structure and electrochemical performance of Li‐rich and Mn‐rich cathodes.