Large-scale synthesis of Li1.15V3O8 nanobelts and their lithium storage behavior studied by in situ X-ray diffraction

Abstract

Li_1.15V₃O₈ nanobelts with length 3 μm, width 200 nm and 20–50 nm in thickness are prepared on a large scale by a tartaric acid-assisted sol–gel technique. They show greater reversibility of the lithium ion insertion/extraction reaction than those synthesized without the addition of tartaric acid. After twenty cycles, the reversible lithium storage capacities of Li_1.15V₃O₈ prepared from tartaric acid assisted and free techniques are 231.0 and 194.5 mAh/g at a current density of 30 mA g⁻¹, respectively. Cycled at 20 mA g⁻¹ in 1.5–4.1 V, Li_1.15V₃O₈ nanobelts can deliver discharge and charge capacities of 297.0 and 298.4 mAh/g, respectively. Increasing the charge/discharge current density to 2400 mA g⁻¹, the lithiation and delithiation capacities of Li_1.15V₃O₈ nanobelts can be mantianed at 184.2 and 184.2 mAh/g, respectively. In situXRD observation reveals that the host structure of Li_1.15V₃O₈ nanobelts will not be destroyed with a discharge process to 0.0 V at 20 mA g⁻¹ or a short circuit for 24 h. Over-lithiation can induce the formation of an inactive compound, leading to poor electrochemical properties of Li_1.15V₃O₈ nanobelts. The first lithiation/delithiation process in 0.0–4.1 V or 1.5–4.1 V is a reversible reaction at a current density of 60 mA g⁻¹, and is composed of reversible single-phase structural evolutions in a high voltage region and two-phase structural transitions in a low voltage region. The electrochemical properties of Li_1.15V₃O₈ nanobelts are poorer at the 10th cycle in 0.0–4.1 V than that obtained in 1.5–4.1 V. In situXRD results indicate that the breakdown of two-phase transition in a low voltage region is the main factor for poor cycleability. Besides, a delay of structural evolution and asymmetry lithiation/delithiation process can be observed at high rates, which may also be responsible for the deterioration of cycleability of Li_1.15V₃O₈ nanobelts.