Comparative study of electrochemical properties of SnS and SnS₂ as anode materials in lithium-ion batteries

Phase pure SnS and SnS₂ were synthesized via the precipitation reaction and investigated as active anode materials for lithium-ion batteries. The crystal structure, morphology and chemical composition of the as-synthesized materials were determined by various physio-chemical techniques such as powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties of the SnS and SnS₂ active anode materials were investigated by galvanostatic cycling with potential limitation, cyclic voltammetry, electrochemical impedance spectroscopy and electrochemical in-situ dilatometry. It was shown that the SnS₂ electrodes exhibit superior cycling performance properties compared to the SnS electrodes. This is due to the higher amount of Li₂S which is produced during the conversion reaction of SnS₂ as well as to the intercalation of Li into the SnS₂ crystal structure prior to conversion, which allows for a finer distribution of Li₂S within the electroactive material.