Aluminum Oxide Coatings on Co-Rich Cathodes and Their Interactions with Organic Electrolyte

Lithium-ion batteries (LIBs) are indispensable in modern energy storage, yet their performance remains limited by the stability and efficiency of their components, particularly the cathode and electrolyte. Transition metal layered oxide cathodes, widely used for LIBs, suffer from several degradation mechanisms, including capacity fading, reactions with the electrolyte, unstable cathode-electrolyte interfaces, and lattice breakdown during cycling. Moreover, the conventional organic electrolytes in LIBs are prone to side reactions, especially at higher states of charge, further hindering performance. In recent years, oxide coatings, such as alumina, have emerged as a promising strategy to enhance cathode durability by forming a protective layer that mitigates detrimental reactions and stabilizes the cathode-electrolyte interphase. We employ <i>ab initio</i> molecular dynamics simulations to investigate the chemical and mechanical behavior of LiCoO₂ cathodes with and without aluminum oxide coatings in contact with an organic electrolyte. We analyze electrolyte interactions with both bare and coated cathode surfaces, focusing on the decomposition of ethylene carbonate and dimethyl carbonate, oxygen species formation, and solvation dynamics. The mechanical robustness of the cathode-coating interface is further assessed through calculations of axial strain and cleavage energy. Our findings reveal that alumina coatings effectively suppress electrolyte degradation and stabilize the cathode structure, particularly at high charge states. The coating's thickness and structural orientation are critical for enhancing mechanical strength and minimizing detrimental reactions at the cathode-electrolyte interface. These insights contribute to developing more durable LIBs by optimizing the interface chemistry and mechanical properties, providing a pathway toward higher energy densities and longer cycle life.