Facile synthesis of ultrasmall Si particles embedded in carbon framework using Si-carbon integration strategy with superior lithium ion storage performance

Downsizing the Si particles, creating conductive carbon matrix and constructing porous expansion space are main ways to enhance lithium ion storage performance of Si-based anode. However, up to now, there are few methods can design Si electrodes integrating these structural features. Here we supply novel ultrasmall Si particles embedded in carbon matrix by using a simple Si-carbon integration strategy. The key to this method is the employment of novel organic/inorganic hybrid building block, i.e., octaphenyl polyhedral oligomeric silsesquioxane (Ph-POSS). Ph-POSS has inorganic –Si8O12 core (SiO1.5) and organic phenyl group shell, simultaneously. The Friedel-Crafts crosslinking of phenyl group shell creates continuous polymeric nanospheres and wraps –Si8O12 core in it. After high-temperature heat treatment and magnesiothermic reduction, the crosslinked polymeric nanosphere will be converted into porous carbon matrix with a surface area of 332 m2 g−1, and the –Si8O12 core (ca. 1.0 nm) will be reduced and in-situ grows to ultrasmall Si particle (4–10 nm). This Si/C nanosphere exhibits superior lithium-ion storage performances. The initial discharge and charge capacities can reach 2139 and 1421 mAh g−1, respectively. After 120 cycles, a remarkable capacity of 738 mAh g−1 remains, which is 2.0 times of the theoretical capacity of graphite.