Yolk-shell-structured SiO2@N, P co-doped carbon spheres as highly stable anode materials for lithium ion batteries

Silicon-based materials have attracted great interest as potential candidates for graphite anodes owing to their extremely high specific capacity and low working potential. Nevertheless, the conventional application of silicon-based anode materials is seriously limited by their poor electrical conductivity and severe volume change. Herein, the development of high-performance anode materials for lithium ion batteries (LIBs) is demonstrated using yolk-shell-structured SiO2@N, P co-doped carbon spheres (SiO2@NPC Y.S.) with an optimized yolk size. The highly controlled structure with sufficient void spaces between the yolk and shell can effectively alleviate the volume swelling of SiO2, thereby improving the long cyclability during repeated lithiation/delithiation. Furthermore, N, P co-doped carbon shells can not only improve the electrical conductivity but also encourage the expansion of the interlayer distance of carbon, which is favorable for both Li + storage and rate performance. SiO2@NPC Y.S. shows a high capacity retention of 94.3% and reversible specific capacity of 705 mAh g−1 over 300 cycles at a current density of 0.1 A g−1. This work would pave the way for the design of anode materials of LIBs with highly controlled yolk-shell structures and heteroatom co-doping.