Novel 3D Si/C/SiOC nanocomposites: Toward electrochemically stable lithium storage in silicon

In this work, we present an easy and environmentally friendly approach to stabilize nanostructured, porous crystalline (Sitc) and amorphous (Sisa) silicon synthesized via magnesiothermic reduction. As matrix, fructose-derived carbon, polymer-derived SiOC ceramic or both, carbon and SiOC, are used. By means of X-ray diffraction and Raman spectroscopy it is found that the crystallinity of Sitc as well as the amorphous character of Sisa is preserved in the final composites. Embedding of crystalline silicon into carbon leads to high initial capacities of ~ 600-650 mAh·g− 1, but only the matrix consisting of carbon and SiOC results in a stable cycling behaviour over 50 cycles with a final capacity of 575 mAh·g− 1. All composites derived from amorphous Sisa show a stable cycling behaviour; the highest, stable capacity of ~ 500 mAh·g− 1 is observed when silicon is covered with carbon and SiOC.