Yolk@Shell SiO /C microspheres with semi-graphitic carbon coating on the exterior and interior surfaces for durable lithium storage

Silicon oxides (SiOx) represent an attractive high-capacity lithium-ion battery (LIB) anode material. However, the huge volume variation of SiOx causes rapid capacity fading and unstable solid electrolyte interface, seriously limiting the practical application. To address the inherent defects of SiOx, herein, we designed a yolk@shell structured SiOx/C anode with semi-graphitic carbon coatings on the exterior and interior surfaces (SiOx/C-CVD) through sol-gel process, selective etching, and chemical vapor deposition. The unique composite nanostructure endows the SiOx/C-CVD high electrical conductivity and excellent structural stability. The as-prepared SiOx/C-CVD composite demonstrates a high reversible capacity (1165 mA h g-1 at 100 mA g-1) as well as outstanding durability (972 mA h g-1 after 500 cycles at 500 mA g-1). Furthermore, the full cells of SiOx/C-CVD//LiCoO2 are also assembled, delivering a high energy density of ~428 W h kg-1 with a stable cycling behavior. The carbon coated yolk@shell design might be applied to optimize the lithium storage performances of other high-capacity anode materials suffering from poor electrical conductivity and large volume variations.