Yolk-shell structured SiO2@NPC nanosphere for lithium ion battery anode material with enhanced cycling performance

초록

Along with the increasing demands for the electric energy, many researchers have been devoted to developing anode materials for lithium ion batteries (LIBs) with high capacity and long cycling stability [1]. Silicon (Si) has been considered as a promising anode material owing to outstanding gravimetric capacity (4200 mAh g?1) compared to commercial graphite anode (372 mAh g?1) [1]. However, huge volume expansion (360%) of Si during the lithiation/delithiation process cause the rapid capacity fading, which seriously hinder the practical application of Si based anode materials on LIBs [2]. Therefore, considerable scientific efforts to control the volume expansion have been performed by designing the structure of Si based active materials [3]. Herein, yolk-shell nanosphere with SiO2 yolk and N,P co-doped carbon shell was prepared through simple hydrothermal and phosphidation process, followed by partial etching strategy. First, SiO2 (SiO2@PPy) nanosphere was synthesized by hydrothermal polymerization, and then it was pyrolyzed with NaH2PO2 to form N,P co-doped carbon (NPC) shell. The yolk-shell structured SiO2@NPC materials with various size of yolk was prepared by partial etching of SiO2 with respect to the different concentration of HF solution. The optimized SiO2@NPC anode material exhibited the excellent gravimetric capacity and long cycling stability, which is attributed to the void space of the unique structures that effectively accommodate large volume expansion of SiO2 during the lithiation/delithiation processes. This work will provide new insight into the preparation and design of other yolk-shell structured anode materials for high-performance LIBs.