In this study, carbon coating was carried out by physical vapor deposition (PVD) on SiOx surfaces to investigate the effect of the deposited carbon layer on the performance of lithium-ion batteries as a function of the asphaltene content of petroleum residues. The petroleum residue was separated into asphaltene-free petroleum residue (ASF) and asphaltene-based petroleum residue (AS) containing 12.54% asphaltene by a solvent extraction method, and the components were analyzed. The deposited carbon coating layer became thinner, with the thickness decreasing from 15.4 to 8.1 nm, as the asphaltene content of the petroleum residue increased, and a highly crystalline layer was obtained. In particular, the SiOx electrode carbon-coated with AS exhibited excellent cycling performance with an initial efficiency of 85.5% and a capacity retention rate of 94.1% after 100 cycles at a current density of 1.0 C. This is because the carbon layer with enhanced crystallinity had sufficient thickness to alleviate the volume expansion of SiOx, resulting in stable SEI layer formation and enhanced structural stability. In addition, the SiOx electrode exhibited the lowest resistance with a low impedance of 23.35 Ω, attributed to the crystalline carbon layer that enhanced electrical conductivity and the mobility of Li ions. This study demonstrated that increasing the asphaltene content of petroleum residues is the simplest strategy for preparing SiOx@C anode materials with thin, crystalline carbon layers and excellent electrochemical performance with high efficiency and high rate performance.

Effect of asphaltene content in petroleum residues on carbon layer properties and the electrochemical performance of SiOx as an anode in lithium-ion batteries
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Preparation of SiOx coated with petroleum residual oil with different asphaltene contents
        2.3 Material characterization
        2.4 Electrochemical measurements
    3 Results and Discussion
        3.1 Characterization of residues with different asphaltene contents
        3.2 Characterization of carbon-coated SiOx with different asphaltene contents
        3.3 Electrochemical performance of SiOx anodes carbon-coated with petroleum residues containing different asphaltene contents
    4 Conclusions
    References

• KyungSoo Kim(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)
• Yebin Lee(Carbon Materials R&D Center, POSCO MC Materials, Gwangyang 57812, Republic of Korea)
• Yongcheol Choi(Carbon Materials R&D Center, POSCO MC Materials, Gwangyang 57812, 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