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.

Oxyfluorination treatment was used to enhance the electrochemical properties of SiOx/C-based lithium-ion battery anode materials by improving the dispersibility of multi-walled carbon nanotubes, which are conductive materials. The dispersibility, chemical, and morphological characteristics of the oxyfluorinated carbon nanotubes were confirmed through various analyses. In addition, the effect of oxyfluorination was analyzed by a lithium-ion battery performance test, and the discharge capacity and cycling stability were significantly improved. The introduction of oxygen functional groups onto the surface of the carbon nanotubes improved their dispersibility. The fluorine functional groups also acted as catalysts for the introduction of these oxygen functional groups onto the surface and improved the cycling stability by forming a LiF-based solid electrolyte interphase layer. The high discharge capacity and improved cycling stability of these lithium-ion batteries were attributed to the enhanced dispersibility of carbon nanotubes induced by oxyfluorination and the resulting enhancement of the 3D network in the anode material promoting the movement of lithium ions and electrons.