Sulfur Loaded by Nanometric Tin as a New Electrode for High-Performance Lithium/Sulfur Batteries

Herein, a composite material formed by coating sulfur on nanometric tin is investigated as the cathode for high-performance lithium/sulfur (Li/S) batteries. The study includes structural and morphological characterization performed by X-ray diffraction and electron microscopy, as well as electrochemical investigation by means of voltammetry, electrochemical impedance spectroscopy, and galvanostatic cycling in lithium cell. The data show an electrode reflecting the crystalline structure of S8 and Sn, with a suitable morphology that consists of micrometric sulfur particles surrounding a metallic core of nanometric tin. This particular configuration leads to optimal behavior in the lithium cell, with a highly reversible electrochemical process evolving between 1.9 and 2.8 V versus Liþ/Li and low polarization. The S-Sn composite shows a favorable electrode/electrolyte interphase having a resistance limited to few ohms after the first activation charge/discharge cycle in the Li/S cell, which allows suitable operation with excellent rate capability and limited capacity fading. Indeed, the cell shows an efficiency approaching 100% upon the first cycle, a maximum specific capacity of about 1200 mAh g1 at C/10 rate, and still a relevant capacity value of about 700 mAh g1 at the relatively high C-rate of 2 C, with suitable retention upon 100 charge/discharge cycles.