VO2/rGO nanorods as a potential anode for sodium- and lithium-ion batteries

Abstract

VO₂ (B) is an interesting cathode candidate in lithium-ion batteries with a high theoretical capacity and fast charge/mass transfer rate. Most of the studies on this material have focused on the lithium insertion reaction in the range of 4.0–1.0 V. In this paper, VO₂/rGO nanocomposite was prepared by a microwave-assisted solvothermal method and investigated in both lithium-ion and sodium-ion batteries as a potential anode. The VO₂ (B) nanorods have an average diameter of ∼200 nm, and is encapsulated by reduced graphene oxide (rGO) nanosheets. Electrochemical results reveal that the VO₂/rGO electrodes exhibit stable cycling and good rate performance in both Li and Na cells. Reversible capacities of 400 mA h g⁻¹ over 400 cycles (vs. Li/Li⁺) and 200 mA h g⁻¹ over 200 cycles (vs. Na/Na⁺) have been achieved, indicating it is potential as an anode candidate either in lithium- or sodium-ion batteries. Nevertheless, the reaction mechanisms seem to be different in Li and Na cells. The crystal structure of VO₂ (B) is maintained at a low discharge potential of 0.05 V in lithium-ion cells, while phase amorphization occurs in sodium-ion cells below 0.5 V. This result is consistent with the previous study on TiO₂, further confirming that some stable metal oxides may show rather different behaviors in Na cells than expected.