Mechanochemical synthesis of SnS anodes for sodium ion batteries

Orthorombic tin (II) sulfide are synthesized by a simple and cost effective mechanochemical method in a high energy ball mill over different time scales. After the detailed characterization by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetricanalysis (TGA), scanning electron microscopy (SEM) and EDX mapping, 2 hours milling time is found to be the optimum as anode in sodium-ion batteries. Later, electrochemical performances are investigated with regards to the binder type; sodium carboxy methyl cellulose (CMC), sodium alginic acid (Na-alginate) and polyvinylidene fluoride (PVdF), in which the best performances are obtained with Na-alginate. Comprehensive electrochemical impedance spectroscopy (EIS) measurements are pursued in order to examine the effect of binders. EIS tests of SnS anodes after C-rate test reveal much bigger resistivity with PVdF binder than that of CMC and Na-alginate. Postmortem surface morphology analysis by means of SEMdemonstrates the self-healing properties of Na-alginate binder with no visible crack formation after cycles. As a whole, more than 300 mAh/g capacity is obtained over 60 cycle at C/5 current density without the help of carbon addition during the synthesis of the SnS composite.