Coal tar pitch modification of the SiO interface enhances the cycling stability of lithium-ion batteries

Coal tar pitch has the advantages of high carbon content, controllability and economy, and broad application prospects in preparing carbon materials and carbon composites. Using pitch to modify the interface of silicon monoxide is an effective strategy to inhibit the expansion of silicon monoxide itself and improve the first Coulomb efficiency and cycle stability. To improve the bonding performance between pitch and matrix materials, this study prepared anode materials by adding binders. Firstly, we prepared a modified pitch with a high softening point, high coking value, and good rheology by air crosslinking at low temperatures. The precursor (SiO@PVP@pitch) was prepared, using polyvinylpyrrolidone (PVP) as a binder and infiltrating combined with silicon monoxide and modified pitch. Through in-situ polymerization, the modified pitch is converted into mesophase pitch and then carbonized at high temperature to obtain SiO/C composites, so that the carbon coating has certain mechanical strength and electrical conductivity. The results of the polarizing microscope show that the carbon coating has a good streamlined structure and the fiber is more delicate. High-resolution transmission electron microscopy (HRTEM) results show that there is a carbon coating layer containing graphite lattice with a thickness of about 90-100 nm on the surface of SiO. The synthesized SiO/C-5∶3-4 h composites showed excellent performance. It has a high specific capacity of 550 mA·h/g at 0.5 A/g, a reversible capacity of 660 mA·h/g, and a capacity retention rate of 83.33% after 200 cycles. The capacity is 472.8 mA·h/g at 1.5 A/g. Electrochemical impedance spectroscopy (EIS) results also prove that the carbon coating layer can effectively improve the conductivity of the composite material, thereby enhancing the cycle stability of the SiO electrode.