First-Principles Investigation on Delithiation Mechanisms in a Li-Rich Monoclinic Li2MoO3 Cathode Material for Li-Ion Batteries

Li2MoO3 is a promising cathode material for high-capacity Li-ion batteries. However, during cycling, migration of Mo to Li sites results in capacity fading. The present study analyzed structural, electronic, electrochemical, and mechanical characteristics of ordered monoclinic C2/m-Li2MoO3 and found that this phase has improved electrochemical properties compared to the rhombohedral R3̅m phase. Nudged elastic band calculations showed that Mo migration to the Li site is less probable in C2/m-Li2MoO3. The charge and chemical bonding analyses during delithiation showed Mo4+/Mo6+ oxidation and partial oxygen oxidation, but no spontaneous oxygen release occurred. The voltage profile calculated using the SCAN + U method exhibits high voltage, and partial W substitution at Mo sites suppresses intralayer Mo migration to the Li site and improves the voltage characteristics. These findings suggest that monoclinic Li2MoO3 is a potential cathode material for high-capacity Li-ion batteries with reduced Mo migration and maintained Mo4+/Mo6+ oxidation and oxygen stability. Moreover, partial W substitution at Mo sites further enhances the electrochemical properties of C2/m-Li2MoO3.