Co-activated Conversion Reaction of MoO2:CoMoO3 as a Negative Electrode Material for Lithium-Ion Batteries.

Extensive studies to develop high-capacity electrodes have been conducted worldwide to meet the urgent demand for next-generation lithium-ion batteries. In this work, we demonstrated a novel strategy to alter the lithiation mechanism of the transition metal oxide to increase the reversible capacity of the electrode material. A representative insertion-type negative electrode material, MoO2, was modified by introducing a heterogeneous element (Co) to synthesize the solid solution of CoO and MoO2 (CoMoO3). CoMoO3 exhibited a notably improved reversible capacity of 860 mA h g-1, attributed to the conversion reaction, in contrast to MoO2 that delivers 310 mA h g-1, as it is limited by the insertion reaction. X-ray absorption spectroscopy and X-ray diffraction demonstrated that CoO is converted to Co and Li2O, amorphizing the host structure, whereas the conversion of MoO2 takes place subsequently. Furthermore, the superior initial Coulombic efficiency of CoMoO3 (84.4%) to that of typical conversion materials is attributed to the highly conductive Co and MoO2, which reinforce the electronic conductivity of the active particles. The results obtained from this study provide significant insights to explore high capacity metal oxides for the advanced lithium-ion batteries.