Thin and Uniform Mesoporous TiO₂-Wrapped MoO₂ Submicrospheres as Anode Materials for Enhanced Electrochemical Performances

Abstract

MoO2 has great potential for applications in rechargeable batteries, supercapacitors, and catalysis. However, its application for a long duration remains a challenge. Here, an effective strategy is presented to enhance its structural and chemical stability by wrapping a thin layer of porous oxide on MoO2 particles. Mesoporous TiO2-coated MoO2 (MoO2@mTiO2) submicrospheres are thus designed and controllably fabricated via kinetics-controlled coating and thermal treatment. The composite submicrosphere is built of a spherical MoO2 core and a thin amorphous mesoporous TiO2 shell with a tunable thickness, showing the enhanced structural and chemical stability. Their formation is attributed to the NH4 +-mediated tiny TiO2 nanoparticle deposition mechanism. Importantly, the MoO2@mTiO2-based electrode for lithium-ion batteries can maintain a high reversible capacity of up to ∼970 mAh g–1 at 1 A g–1 even after 380 cycles, which is much higher than that of the bare MoO2 microsphere-based electrode, exhibiting excellent cycling performance. Further experiments have revealed that there exists an optimal TiO2 shell thickness (about 12 nm), and overly thin or thick TiO2 shells are unfavorable to a long cycling performance with high capacity. In addition, this MoO2@mTiO2 electrode can always maintain a high reversible capacity of above 200 mAh g–1 at 1 A g–1 even after 1000 cycles for sodium-ion batteries, showing a good practical prospect. This study provides not only a facile route for the fabrication of MoO2@mTiO2 submicrospheres but also a potential electrode material with enhanced structural and chemical stability for lithium (or sodium)-ion batteries.