Li+ storage properties of SiO2@C core-shell submicrosphere and its hollow counterpart synthesized by molecular self-assembly in wet-chemistry condition as anodes for LIBs

SiO2@C core-shell submicrospheres (SiO2@C) were fabricated via molecular self-assembly process in wetchemistry condition and followed by post-calcination. SEM and TEM indicated the outer diameter of SiO2@C is similar to 300-400 nm. The diameter of inner SiO2 core can be controlled from maximum size to zero by NaOH solution etching. XRD, TG-DSC, BET, Raman and XPS were adopted to reveal its microstructure and elemental composition. Systematic electrochemical tests manifested that the specific capacity of SiO2@C reduces at the beginning then increases with the decrease of SiO2 core diameter. The underlying Li+ storage mechanism is discussed and analyzed, which illustrates that the effective utilization of active sites is the key for electrochemical performance when SiO2@C used as anode material for LIBs. And the completely etched hollow mesoporous carbon sphere without SiO2 core (HMCS, SiO2@C-12 h) exhibited the highest capacity and rate capability (349.2 mA h/g at 100 mA/g after 200 cycles; 316.0 mA h/g at 400 mA/g), which is due to the effective Li+ active sites benefitted from its conductive and porous carbon network. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

SiO2@C core-shell submicrospheres were fabricated via molecular self-assembly process, with the ability to control the inner core diameter and enhance electrochemical performance. Compared to the completely etched hollow mesoporous carbon sphere, it showed higher capacity and rate capability.