Synthesis of Yolk-Shell-Structured SiO₂/C Particles Using a Heat-Treated Mixture of Polyvinylidene Fluoride and SiO₂ Particles

This study devised a method for manufacturing yolk-shell-structured SiO2/C composite particles by a simple heat treatment process using a mixture of polyvinylidene fluoride (PVDF) and SiO2. This simple technique for fabricating yolk-shell structures involves the simultaneous carbonization of a carbon source and etching of SiO2 during the heat treatment. During the fabrication process, PVDF and SiO2 particles were mixed and heat treated, and the changes in the mixture before and after the heat treatment were examined by mass measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) analysis. The mass of the mixture, which decreased after heat treatment, decreased even further at 400degree celsius because of the active thermal decomposition of PVDF in particular. These results, which were confirmed through TEM, were attributed to the loss of decomposed gases and SiO2 etching by HF gas. As a result, the yolk-shell-structured SiO2/C composite particles are formed a carbonized carbon layer through the heat treatment of PVDF while empty spaces are formed by etching the core SiO2 with HF generated by the thermal decomposition of PVDF. Thus, carbonization and SiO2 etching were simultaneously performed in a single heat treatment process to fabricate the yolk-shell-structured particles.