Fabrication of Yolk-Shell Silicon@Carbon Anode Via Iodination Treatment

Abstract

As the demand for lithium ion batteries (LIBs) with high energy density increases, silicon has attracted great attention as a next-generation anode material due to its high theoretical capacity of 4200mAh/g. However, silicon has been suffered from poor cycleability due to a large volume change during the lithiation process. To tackle this critical problem, some methods have been used, such as nano-sized silicon, porous silicon, and a hollow carbon/silicon composite. However, nano-sized silicon is expensive for commercialization. In addition, the harmful hydrogen fluoride (HF) acid is commonly used to etch silicon oxides for porous structure. In this study, a yolk-shell structure with a space between the carbon shell and micro-sized silicon was made without HF. The poly(vinyl alcohol) (PVA) coated silicon was treated with an iodine followed by stabilization at 200 oC. The iodination process converts the chemical structure of PVA to polyene structure and enhances the carbon yield. The yolk-shell structure was formed by the eliminating an untreated PVA layer during the carbonization process. The prepared yolk-shell silicon/carbon composite worked well as an anode electrode and showed a high initial discharge capacity of 3266 mAh/g and maintained 1700 mAh/g until 200 cycles.