Rational structure design to realize high-performance SiO_x@C anode material for lithium ion batteries

Silicon suboxide (SiO_x) is considered to be one of the most promising materials for next-generation anode due to its high energy density. For its preparation, the wet-chemistry method is a cost-effective and readily scalable route, while the so-derived SiO_x usually shows lower capacity compared with that prepared by high temperature-vacuum evaporation route. Herein, we present an elaborate particle structure design to realize the wet-chemistry preparation of a high-performance SiO_x/C nanocomposite. Dandelion-like highly porous SiO_x particle coated with conformal carbon layer is designed and prepared. The highly-porous SiO_x skeleton provides plenty specific surface for intimate contact with carbon layer to allow a deep reduction of SiO_x to a low O/Si ratio at relatively low temperature (700 °C), enabling a high specific capacity. The abundant mesoscale voids effectively accommodate the volume variation of SiO_x skeleton, ensuring the high structural stability of SiO_x@C during lithiation/delithiation process. Meanwhile, the three-dimensional (3D) conformal carbon layer provides a fast electron/ion transportation, allowing an enhanced electrode reaction kinetics. Owing to the optimized O/Si ratio and well-engineered structure, the prepared SiO_x@C electrode delivers an ultra-high capacity (1,115.8 mAh·g^-1 at 0.1 A·g^-1 after 200 cycles) and ultra-long lifespan (635 mAh·g^-1 at 2 A·g^-1 after 1,000 cycles). To the best of our knowledge, the achieved combination of ultra-high specific capacity and ultra-long cycling life is unprecedented.