CoS2 is a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, its practical application is hampered by severe volume expansion during cycling. In this study, fluorine-doped carbon-coated CoS2 (F-CoS2@C) was synthesized via NaCl template-assisted carbon coating using petroleum-derived pyrolyzed fuel oil, followed by CF4 plasma treatment. The proposed method of synthesis enables control of the carbon layer thickness, formation of a void structure, and introduction of fluorine functional groups. F–CoS2@C delivered 295 mAh/g at 5 A/g and retained 375 mAh/g after 500 cycles at 1 A/g. The enhanced electrochemical performance is attributed to the void carbon structure and fluorine-induced interfacial stabilization. The carbon structure increased electrolyte penetration and electrical conductivity, and mitigated volume changes. Fluorine doping promoted the formation of a LiF-rich solid electrolyte interphase layer and enhanced the electronic transport by semi-ionic C-F bonds. This study offers a promising strategy for the development of transition metal sulfide/carbon composites as high-performance LIB anodes.

Design of F-doped  with void structure as a high-performance anode for lithium-ion battery
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Fabrication of CoS2, CoS2@C, and F-CoS2@C
        2.3 Characterization
        2.4 Electrochemical measurements
    3 Results and discussion
        3.1 Structure and characterization
        3.2 Electrochemical properties
    4 Conclusion
    References

• Bo Kyoung Kim(Research Center for Materials Analysis, Korea Basic Science Institute, Daejeon 34133, Republic of Korea)
• Tae-Sung Bae(Research Center for Materials Analysis, Korea Basic Science Institute, Daejeon 34133, Republic of Korea)
• Young-Seak Lee(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea, Institute of Carbon Fusion Technology (InCFT), Chungnam National University, Daejeon 34134, Republic of Korea) Corresponding author
• Eunseon Chae(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• In Woo Lee(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Seongjae Myeong(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Minah Kang(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)