Nano-(V_½Sb_½Sn)O₄: a high capacity, high rate anode material for Li-ion batteries

Abstract

Vanadium antimony tin oxide, M (micron size)- (V_½Sb_½Sn)O₄ with tetragonal rutile structure is prepared for the first time. The N (nanosize, 10-20 nm)-analogue is obtained by high energy ball milling of the above. They are characterized by Rietveld refinement of the X-ray diffraction data, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), density and BET surface area studies. The Li-cycling properties were studied at ambient temperature (24 °C) and at 54°C by galvanostatic discharge–charge cycling and cyclic voltammetry. Nano-(V_½Sb_½Sn)O₄ shows stable cycling performance at 24°C with capacities 450, 435 and 360 (±5) mA h g⁻¹ at rates of 0.43, 1.0 and 3.5 C, respectively, in the range, 0.005–1.0 V vs. Li. These values are stable up to 100 cycles at 0.43 C and up to at least 50 cycles at 1 C and 3.5 C. At 54 °C and at 0.43 C, N-(V_½Sb_½Sn)O₄ delivers a stable capacity of 440 (±5) mA h g⁻¹ in the range, 5–100 cycles. Under similar conditions the cycling performance of M-(V_½Sb_½Sn)O₄ is inferior to that of the N-analogue. The M- and N-(V_½Sb_½Sn)O₄ showed main cathodic and anodic peaks at ~0.2 V and ~0.5 V, respectively, by CV. Complementary impedance studies are reported at various voltages and as a function of cycle number to support the Li-cycling mechanism involving alloying–de-alloying reactions of Sn and Sb with Li using (VO) as an inert matrix.