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.

Porous hard carbon has recently gained attention as an anode material for KIB because of its superior potassium ion storage performance. In this study, an efficient method for producing polyethylene-based hollow porous carbon is presented. Partial sulfonation was applied, and the porosity of the resulting carbon material was regulated by the sulfonation time. A hollow structure with the high specific surface area of 173.3 m2/g was achieved via partial sulfonation and carbonization without additional activation. Using polyethylene (PE)-based porous carbon as an anode material for KIB, a high specific discharge capacity of 187 mAh/g and excellent rate capability at 1000 mA/g were achieved. Moreover, potassium-ion storage mechanisms were identified and compared with those of non-porous PE-based carbon anodes. This study provides an effective method for preparing porous PE-based carbon with superior energy storage performance.