Exploring lithium storage mechanism and cycling stability of MoO2 metal oxide anode composited with Li2MoO4

Metal oxides are considered one of the most promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacity, low cost and abundant reserves. Unfortunately, poor cycle and rate performance have limited their use as anode materials on a large scale. Here, we report the MoO2 and Li2MoO4 composite material as an anode for LIBs. The prepared MoO2-Li2MoO4 composite demonstrates initial discharge capacity of over 700 mAh g+1 at a current density of 500 mA g+1 and an initial coulombic efficiency of 79.5 %, which out-performs the bare MoO2 and Li2MoO4 alone. In addition, the MoO2-Li2MoO4 composite material exhibits excellent rate performance, at a 5C high rate (1C = 500 mA g+1), a capacity of more than 500 mAh g+1 can be obtained. The resulting MoO2-Li2MoO4 composite material successfully resolves an issue of poor Li+ diffusion kinetics of MoO2-based materials. The lithium-ion storage mechanism of the MoO2-Li2MoO4 composite was also explored through an in situ XRD characterization, that MoO2 is first converted to Li0.98MoO2 and small amount of Mo metal at low potentials, which can be reversibly returned to MoO2 on charge, and Li2MoO4 is irreversibly converted into amorphous phase in first discharge. It is suggested that the composition idea can be extended to other metal oxide anode materials.