Li-storage and cycling properties of Sn–Sb-mixed oxides, (M1/2Sb1/2Sn)O4, M = In, Fe

Abstract

The mixed oxide compounds, (M1/2Sb1/2Sn)O4, M = In and Fe are prepared by the high-temperature solid-state reaction, at 800 °C for M = In and at 1,150 °C for M = Fe. High-energy ballmilling is used to reduce the particle size to nm-range. The compounds are characterized by X-ray diffraction, Rietveld refinement, scanning electron microscopy, and Brunauer–Emmett–Teller surface area methods. The Li-storage and cycling properties of the bare and ballmilled compounds are evaluated by galvanostatic cycling at ~0.15 C and in the voltage ranges 0.005–1.0 and 0.005–1.2 V vs. Li up to 50 (or 100) cycles and by cyclic voltammetry (CV) at room temperature. Effect of electrode heat treatment and carbon nanotube (CNT) addition is also studied. Initial reversible capacities in the range 425–550 mAh g−1 are observed depending on the metal (M) upper cut-off voltage, CNT content and electrode heat treatment. Ballmilled (In1/2Sb1/2Sn)O4 showed a stable capacity of 445 mAh g-1 up to 30 cycles and 5 % capacity fading after 50 cycles. In all other cases, capacity fading is observed ranging from 9 to 60 %. The CV showed that the main cathodic and anodic peaks occur at 0.15–0.25 V and ~0.5 V vs. Li, respectively, for both M. The reaction mechanism involves alloying–de-alloying reactions of Sn and In with Li3Sb or Fe acting as conducting matrix, and corroborated by the ex-situ X-ray diffraction data on (In1/2Sb1/2Sn)O4.