Synthesis of nanosized nickel sulfide in high-boiling solvent for all-solid-state lithium secondary batteries

Abstract

Nickel sulfide nanoparticles were synthesized by thermal decomposition of nickel acetylacetonate in a mixed solution of 1-dodecanethiol and a high-boiling solvent. The crystal phase and morphology of the obtained samples by changing the reaction time, reaction temperature, and the kind of the solvents were characterized by X-ray diffraction measurements and transmission electron microscopy. By using oleylamine as a coordinating solvent, Ni₉S₈ nanorods with the size of about 100 nm were obtained at 280 °C for 5 hours. On the other hand, NiS nanoparticles with the size of about 50 nm were obtained by using 1-octadecene as a noncoordinating solvent. Nickel sulfide crystals with different phase and morphology were obtained by selecting the solvent. The all-solid-state cells using NiS nanoparticles with the size of about 50 nm as active materials were fabricated. The 80Li₂S·20P₂S₅ (mol%) glass–ceramic was used as a solid electrolyte. The cell Li–In/NiS exhibited the initial discharge capacity of 780 mA h g⁻¹ at 0.13 mA cm⁻² and the good cycle performance during 20 cycles.