LixV2O5/LiV3O8 nanoflakes with significantly improved electrochemical performance for Li-ion batteries

Abstract

Poor cycling stability and rate capability are the main challenges for LiV₃O₈ as the cathode material for Li-ion batteries. Here a novel strategy involving the self-transformation of superficial LiV₃O₈ in a reducing atmosphere (H₂–Ar) was reported to fabricate Li_xV₂O₅/LiV₃O₈ nanoflakes. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) results demonstrate that Li_xV₂O₅/LiV₃O₈ nanoflakes could be in situ formed and that the thickness of the Li_xV₂O₅ layer is controllable. When used as a cathode for a Li-ion battery, the Li_xV₂O₅/LiV₃O₈ nanoflakes exhibit significantly improved cycling stability with a capacity retention of ca. 82% over 420 cycles at a 1 C-rate (1 C = 300 mA g⁻¹), and much better rate performance compared with bare LiV₃O₈. The improvement of the electrochemical performance could be attributed to the unique core–shell structure, in which the ultrathin Li_xV₂O₅ layer could not only protect the internal LiV₃O₈ from dissolution, but also increase the Li ion diffusion coefficient and suppress the charge-transfer resistance, as verified by electrochemical impedance spectroscopy (EIS) and XRD results.