Synthesis of Needle like and Platelike SnS Active Materials in High-Boiling Solvents and Their Application to All-Solid-State Lithium Secondary Batteries

Tin sulfide (SnS) particles were synthesized by thermal decomposition of tin acetate in a mixed solution of 1-dodecanethiol, one of coordinating solvents such as trioctylphosphine and oleylamine, and 1-octadecene as a non-coordinating solvent at 280 degrees C for 2 h. The morphology of the obtained SnS particles was determined by transmission electron microscopy. Needlelike SnS particles were obtained by using trioctylphosphine as a coordinating solvent. On the other hand, platelike SnS particles were obtained by using oleylamine. The SnS particles were formed by diffusion of sulfur derived from 1-dodecanethiol into Sn particles. In addition, the aspect ratio of needlelike SnS particles was affected by the amount of 1-dodecanethiol as a sulfur source. The all-solid-state cells using SnS particles with the different morphology as an active material were fabricated. The initial discharge capacity of the all-solid-state cell using needlelike SnS particles as an active material was ca. 1000 mAh g(-1), which was larger than that of the cell with platelike SnS particles under the current density of 0.13 mA cm(-2) at 25 degrees C.