Tin sulfide (SnS) nanorods: structural, optical and lithium storage property study

Abstract

Tin mono-sulfide (SnS) nanorods (NRs) have been successfully synthesized through a solvothermal process using hydrated tin(II) chloride and sodium sulfide as precursors and N,N-dimethyl formamide (DMF) as solvent. The Reitveld refined powder X-ray diffraction (PXRD), Raman and ¹¹⁹Sn solid-state NMR experiments have confirmed the presence of a SnS phase with Pnma space group and a SnS₂ phase with Pm1 space group as a minor impurity. HRTEM and HRSEM studies have confirmed the nanoparticle shape as nanorods (NRs). The growth of the NRs has been explained from the observation that by increasing the solvothermal temperature, nanorods grow preferentially in the [100] direction. Optical properties of the SnS nanorods were measured and it was found that all NRs have an indirect band gap in the range of 1.10 eV to 1.2 eV. The electrochemical properties for lithium storage (half-cell configuration) have been tested against Li/Li⁺ using conventional polyvinylidene fluoride (PVDF) binder and an eco-friendly, low cost binder, carboxy methyl cellulose (CMC). After fifty cycles of charge–discharge, the CMC binder electrode shows a superior electrochemical charge storage property of 591 mA h g⁻¹ compared with 385 mA h g⁻¹ for the PVDF binder electrode, at 160 mA g⁻¹ current rate. At a high current rate of 350 mA g⁻¹, the SnS NRs with the CMC binder shows a discharge capacity of 565 mA h g⁻¹ after 50 cycles, therefore exhibiting excellent properties for a lithium battery anode as it can maintain a high capacity and coulombic efficiency continuously for 50 cycles.