Crystallinity-dependent lithium storage behavior of molybdenum dioxide for lithium rechargeable batteries

초록

Molybdenum dioxide (MoO2) is a promising anode material owing to its electronic conductivity and a theoretical capacity of 838 mAh g−1. However, MoO2 shows suppressed conversion at room temperature because strong Mo–O bonding hinders bond cleavage. This study shows that lowering crystallinity activates conversion. Low-crystalline MoO2 (lc-MoO2) delivers 937.4 mAh g−1 at 100 mA g−1 in the 100th cycle (91.6% retention vs the 10th) and 404.5 mAh g−1 at 5000 mA g−1, outperforming crystalline MoO2. The defect-rich framework lowers the barrier for Mo–O cleavage and provides flexibility, while short diffusion paths and a larger surface area increase the surface-capacitive contribution and accelerate Li storage. Synchrotron-based X-ray absorption spectroscopy and electron microscopy reveal an evolution toward MoO3 that correlates with increased capacity. Lithium insertion, partial conversion, and gel-like film formation account for the high reversible capacity. These findings highlight crystallinity control as a design parameter for oxide anodes in lithium-ion batteries.

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