Thread like structured VO₂ microspheres for improved lithium-ion storage kinetics and stability

Among vanadium-based materials, VO₂(B), sharing octahedral VO₆ structure with cavities, are considered as cathode materials due to their high capacity and multiple oxidation state. However, it has its own limitations such as low cyclic stability and sluggish charge storage kinetics arising from large structural deformation and poor electrical conductivity. In order to resolve these problems, we report a microsphere of thread like structured VO₂(B) consisting of interconnected particles each other, providing continuous and facile electron and ion transport pathway. The robust internetworked microspherical structure leads to prevent the drastic volume variation during Li insertion/de-insertion process. More specifically, the as-synthesized VO₂(B) displays high capacity of 225.6 mAh g⁻¹ at 50 mA g⁻¹ with a Columbic efficiency of 98%, high rate retention of 70% at 300 mA g⁻¹, and good cycle stability of 72% after 350 cycles at 300 mA g⁻¹. In addition, their structural and phase reversibility are confirmed by the in-situ XRD of VO₂(B), where position of crystalline (002) peak after several electrochemical processes nearly returns on the origin position during Li insertion/de-insertion.