Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni3Co6S8-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni3Co6S8@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni3Co6S8@C-YS exhibited an impressive reversible capacity of 525.2 mA h g-1 at a current density of 0.5 A g-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni3Co6S8 yolk shell nanopowder (Ni3Co6S8-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni3Co6S8@C-YS were attributed to the pitchderived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

1. Introduction
2. Experimental
3. Results and Discussion
4. Conclusion
Acknowledgement

• 서효영(충북대학교 도시에너지환경 융합학부) | Hyo Yeong Seo (Department of Urban, Energy, and Environmental Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic of Korea)
• 박기대(충북대학교 도시에너지환경 융합학부, 충북대학교 신소재공학과) | Gi Dae Park (Department of Urban, Energy, and Environmental Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic of Korea, Department of Advanced Materials Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic of Korea) Corresponding Author