Tin and graphite based nanocomposites: Potential anode for sodium ion batteries

Pure tin (Sn) and a homogeneous nanocomposite of tin and graphite (C), denoted as Sn/C, have been studied as a suitable anode for sodium ion batteries. The Sn/C nanocomposites have been synthesized by high energy mechanical milling (HEMM) of pure Sn and graphite of nominal composition C-70 wt.% Sn. Pure microcrystalline Sn (<= 44 mu m) exhibits a 1st discharge capacity similar to 856 mAh g(-1) which is close to the expected theoretical capacity, however, it shows a large 1st cycle irreversible loss (similar to 67%) and the anticipated inevitable rapid fade in capacity expectedly due to structural failure of the electrode. On the other hand, the resultant Sn/C based nanocomposite, synthesized by HEMM after 1h of milling, exhibits a 1st cycle discharge capacity similar to 584 mAh g(-1) with a 1st cycle irreversible loss similar to 30%. The Sn/C nanocomposite shows a 1st cycle charge capacity of similar to 410 mAh g(-1) with improved capacity retention in comparison to pure Sn displaying 0.7% fade in capacity per cycle up to 20 cycles when cycled at a rate of similar to C/8. Scanning electron microscopy (SEM) analysis indicates that the structural integrity and microstructural stability of the Sn/C nanocomposite during the alloying/dealloying processes appear to be the primary factors contributing to the good cyclability observed in the above HEMM derived nanocomposite suggesting its promise as a potential anode for Na-ion systems. (C) 2012 Elsevier B.V. All rights reserved.