SiOx/C Composite Anode for Lithium-Ion Battery with Improved Performance Using Graphene Quantum Dots and Carbon Nanoparticles

In this study, a composite was manufactured by mixing graphene quantum dots, silicon oxide, and carbon nanoparticles, and the characteristics of the anode materials for secondary batteries were examined. To improve the capacity of the graphene quantum dot (GQD) anode material, the added silicon oxide content was varied among 0, 5, 10, 15, and 30 wt%, and carbon nanoparticles were added as a structural stabilizer to alleviate silicon oxide volume expansion. The physical properties of the prepared GQD/SiOx/C composite were investigated through XRD, SEM, EDS, and powder resistance analysis. Additionally, the electrochemical properties of the manufactured composite were observed through an analysis of the charge–discharge cycle, rate, and impedance of a lithium secondary battery. In the GQD/SiOx/C composite, by adding carbon nanoparticles, an internal cavity was formed that can alleviate the volume expansion of silicon oxide, and the carbon nanoparticles and silicon oxide particles were uniformly distributed. The formed internal cavity had a silicon oxide content of 5 wt%. Low initial efficiency was observed, and above 30 wt%, low cycle stability was observed. The GQD/SiOx/C composite with 15 wt% of silicon oxide added showed an initial discharge capacity of 595 mAh/g, a capacity retention rate of 92%, and a rate characteristic of 81 at 2 C/0.1 C. Silicon oxide was added to improve the capacity of the anode material, and carbon nanoparticles were added as a structural stabilizer to buffer the volume change of the silicon oxide. To use GQD/SiOx/C composite as a highly efficient anode material, the optimal silicon oxide content and carbon nanoparticle mechanism as a structural stabilizer were discussed.