Synthesis of NiS–carbon fiber composites in high-boiling solvent to improve electrochemical performance in all-solid-state lithium secondary batteries

Newly designed composites of nickel sulfide (NiS) and vapor grown carbon fiber (VGCF) for use in all-solid-state lithium secondary batteries were synthesized using thermal decomposition of nickel acetylacetonate and 1-dodecanethiol in a mixture of VGCF and 1-octadecene. X-ray diffraction measurements and transmission electron microscopy revealed that NiS nanoparticles of 50 nm diameter were grown on the surface of vapor grown carbon fiber. All-solid-state cells using 80Li2S·20P2S5 (mol%) glass–ceramic were fabricated as a solid electrolyte. The cell using the mixture of the NiS–VGCF composite and the solid electrolyte as a working electrode showed initial discharge capacity of 590 mAh g−1 at 1.3 mA cm−2, and exhibited better cycle performance than the cell using the mixture of NiS, solid electrolyte, and VGCF. Electrochemical performance in all-solid-state batteries was improved by forming a favorable solid–solid interface between NiS active materials and VGCF as electron conduction paths in the working electrode.