Nano-(V1/2Sb1/2Sn)O-4: a high capacity, high rate anode material for Li-ion batteries

Vanadium antimony tin oxide, M (micron size)-(V1/2Sb1/2Sn)O-4 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 degrees C) and at 54 degrees C by galvanostatic discharge-charge cycling and cyclic voltammetry. Nano-(V1/2Sb1/2Sn)O-4 shows stable cycling performance at 24 degrees C with capacities 450, 435 and 360 (+/- 5) mA h g(-1) at rates of 0.43, 1.0 and 3.5 degrees C, respectively, in the range, 0.005-1.0 V vs. Li. These values are stable up to 100 cycles at 0.43 degrees C and up to at least 50 cycles at 1 degrees C and 3.5 degrees C. At 54 degrees C and at 0.43 C, N-(V1/2Sb1/2Sn)O-4 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-(V1/2Sb1/2Sn)O-4 is inferior to that of the N- analogue. The M- and N-(V1/2Sb1/2Sn)O-4 showed main cathodic and anodic peaks at similar to 0.2 V and similar to 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.