Improved Electrochemical Performance of SnS2 for Li-Ion Battery Anode By Engineering Interlayer Spacing

Abstract

Keywords: layered SnS2, organic-inorganic composites, lithium-ion batteries, polymer restacking The unique layered structure of transition metal dichalcogenides (TMDs) has historically been of great interest for energy storage applications because of the feasible ion intercalation/deintercalation within the van der Waals (vdW) gaps. Tin disulfide (SnS2) is a TMD that approaches twice the theoretical reversible gravimetric capacity of carbon (645 mAh/g vs. 372 mAh/g),1,2 the current anode of choice for lithium-ion batteries.2 In the present study, pristine SnS2 nanoflakes were prepared using a hydrothermal reaction. Subsequent exfoliation was achieved by intercalating n-butyllithium into the vdW gaps and reacting the LixSnS2 with dimethylformamide and distilled H2O. Once exfoliated, polymer was introduced either by direct addition or by polymerizing monomer in solution. X-ray diffraction shows a modified d-spacing along the c-direction of the resultant powders, indicative of successful restacking. Coin cells were constructed as a cathode/electrolyte/Li-metal configuration, with LiPF6 as Li salt and EC/DEC as solvent. Electrochemical tests were conducted from 0.1 V to 3.0 V at 0.1C-rate. Galvanostatic Intermittent Titration Technique was also employed to determine the diffusivity of Li-ions in the active material during cycling. By selectively expanding the vdW gaps, we probed the structure-property relationship of this nanocomposite material, and correlated how this expansion affects the barrier to Li+diffusion.