Effect of pore lengths on the reduction degree and lithium storage performance of Mesoporous SiOx nanomaterials

Abstract

Mesoporous SiOx nanomaterials are regarded as promising lithium storage materials due to the unique architecture consisting of ultrasmall Si nanocrystals in mesoporous SiO2 matrix where the oxygen content plays a paramount role in the lithium storage performance. Different from previous works on the extrinsic reduction conditions of SiO2 precursors, this work investigates the effect of inner structures on the reduction degree and performances for the first time. Mesoporous SBA-15 rods with tunable pore lengths are prepared as precursors for SiOx. It is found that the O/Si atomic ratios decrease from 1.31 to 0.73 as the pore lengths reduce from 3 to 0.5 μm. With the shortest pore length, SiO0.73 nanorods exhibit the best lithium storage performance. Moreover, SiO0.73 nanorods are further modified by carbon nanolayers and present a remarkably improved performance (595 mAh g−1 after 60 cycles). This study can help us further understand the role of pore lengths on the reduction degree of SiO2 and enlighten us on adopting advanced SiO2 precursors with preferable inner structures.