Double-buffer-phase embedded Si/TiSi2/Li2SiO3 nanocomposite lithium storage materials by phase-selective reaction of SiO with metal hydrides

Abstract

Silicon monoxide (SiO)-based anode materials have been extensively investigated as high-capacity anode materials for lithium-ion batteries; however, they suffer from low initial Coulombic efficiency (ICE). Solid-state prelithiation of SiO with LiH has shown some promise to address this shortcoming, and further improvement in long-term cycle performance is a necessary step toward commercial application. Here, we propose a double-buffer-phase embedded Si/TiSi2/Li2SiO3 nanocomposite materials prepared by phase-selective reaction of SiO with metal hydrides to improve both ICE and cycle performance. The resulting Si/TiSi2/Li2SiO3 nanocomposite material outperformed prelithiated SiO with LiH composed of nanoscale Si and Li2SiO3 phase for up to 500 cycles without a significant decrease in ICE. The nano-scale TiSi2 phases formed by the reaction of Si phase in SiO with TiH2 played a key role in boosting the capacity retention of the Si/TiSi2/Li2SiO3 nanocomposite by providing a robust mechanical buffer to sustain the physical integrity of the electrode against large volume changes of Si phase during cycling. In addition to superior cycle performance, Si/TiSi2/Li2SiO3 nanocomposite demonstrated improved thermal stability at elevated temperatures and greater rate capability compared with pristine and prelithiated SiO materials, changes that can be attributed to newly introduced TiSi2 buffer phase.