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 mixture and 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 (≤44μm) exhibits a 1st discharge capacity ∼856mAh/g which is close to the expected theoretical capacity, however, it shows a large 1st cycle irreversible loss (∼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 mixture, synthesized by HEMM after 1h of milling, exhibits a 1st cycle discharge capacity ∼584mAh/g with a 1st cycle irreversible loss ∼30%. The Sn/C mixture shows a 1st cycle charge capacity of ∼410 mAh/g 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 ∼C/8. Scanning electron microscopy (SEM) analysis indicates that the structural integrity and microstructural stability of the Sn/C mixture during the alloying/dealloying processes appear to be the primary factors contributing to the good cyclability observed in the above HEMM derived mixture suggesting its promise as a potential anode for Na-ion systems.
Journal of Power Sources
Available online 16 October 2012
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