Amorphous SiO₂ in tunnel-structured mesoporous carbon and its anode performance in Li-ion batteries

Highlights: • Amorphous SiO₂ was uniformly embedded in the tunnel wall of mesoporous carbon. • This structural design activate insulating SiO₂ (670 mAh g⁻¹) and accommodate its volume variation during cycling. • This impregnation concept can be applied to design composites for other advanced electrode materials. In this work, amorphous silica was uniformly embedded at the nano-scale in the tunnel wall of mesoporous carbon, with no free or aggregated silica or carbon particles in the cavity of the tunnels. The tunnel provides sufficient space for the volume expansion of SiO₂, while the carbon skeleton forms electric conducting paths for the electrochemical reaction/activation of the silica. Therefore, impregnation of inactive and insulating SiO₂ particles in active and conducting mesoporous carbon (SiO₂-MC) is beneficial for improving the electrochemical activity and cycling performance of the former as an LIB anode. As a result, the SiO₂-MC composite delivers a reversible capacity of 670 mAh g⁻¹, much higher than that of the composite (SiO₂ + MC) containing SiO₂ aggregates (~ 300 mAh g⁻¹). This impregnation concept can be applied in the structural design of composite electrodes for other secondary batteries and preparation of high-efficiency catalysts.