Synthesis of Needlelike 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 noncoordinating solvent at 280 °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 °C.