Preparation of a Si/SiO2 -Ordered-Mesoporous-Carbon Nanocomposite as an Anode for High-Performance Lithium-Ion and Sodium-Ion Batteries.

In this work, an Si/SiO2 -ordered-mesoporous carbon (Si/SiO2 -OMC) nanocomposite was initially fabricated through a magnesiothermic reduction strategy by using a two-dimensional bicontinuous mesochannel of SiO2 -OMC as a precursor, combined with an NaOH etching process, in which crystal Si/amorphous SiO2 nanoparticles were encapsulated into the OMC matrix. Not only can such unique porous crystal Si/amorphous SiO2 nanoparticles uniformly dispersed in the OMC matrix mitigate the volume change of active materials during the cycling process, but they can also improve electrical conductivity of Si/SiO2 and facilitate the Li+ /Na+ diffusion. When applied as an anode for lithium-ion batteries (LIBs), the Si/SiO2 -OMC composite displayed superior reversible capacity (958 mA h g-1 at 0.2 A g-1 after 100 cycles) and good cycling life (retaining a capacity of 459 mA h g-1 at 2 A g-1 after 1000 cycles). For sodium-ion batteries (SIBs), the composite maintained a high capacity of 423 mA h g-1 after 100 cycles at 0.05 A g-1 and an extremely stable reversible capacity of 190 mA h g-1 was retained even after 500 cycles at 1 A g-1 . This performance is one of the best long-term cycling properties of Si-based SIB anode materials. The Si/SiO2 -OMC composites exhibited great potential as an alternative material for both lithium- and sodium-ion battery anodes.