Double Core-Shell Si@C@SiO2 for Anode Material of Lithium-Ion Batteries with Excellent Cycling Stability.

Lithium-ion batteries (LIBs) composed of silicon (Si) anodes suffer from severe capacity decay because of the volume expansion deriving from the formation of Li15 Si4 alloy. In this study, we prepared a double core-shell Si@C@SiO2 nanostructure by the modified Stöber method. In the process of Si lithiation, the carbon layer alleviates the large pressure slightly then the silica shell restricts the lithiation degree of Si. The combination of carbon interlayer and silica shell guarantees structural integrity and avoids further decay of capacity because of the formation of stable solid-electrolyte interphase (SEI) films. The resultant Si@C@SiO2 presents remarkable cycling stability with capacity decay of averagely 0.03 % per cycle over 305 cycles at 200 mA g-1 , an improvement on Si@C (0.22 %) by more than a factor of 7. This encouraging result demonstrates that the designation involved in this work is effective for mitigating the capacity decay of Si-based anodes for LIBs.