title: Lithium silicide nanocrystals: synthesis, chemical stability, thermal stability, and carbon encapsulation.
abstract: Lithium silicide (LixSi) is the lithiated form of silicon, one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs). In contrast to silicon, LixSi has not been well studied. Herein we report a facile high-energy ball-milling-based synthesis of four phase-pure LixSi (x = 4.4, 3.75, 3.25, and 2.33), using hexane as the lubricant. Surprisingly, the obtained Li3.75Si phase shows significant downward shifts in all X-ray diffraction peak positions, compared with the standard. Our interpretation is that the high-energy ball-mill-synthesized Li3.75Si presents smaller internal pressures and larger lattice constants. The chemical-stability study reveals that only surface reactions occur after Li4.4Si and Li3.75Si are immersed in several battery-assembly-related chemicals. The thermal-stability study shows that Li4.4Si is stable up to 350 °C and Li3.75Si is stable up to 200 °C. This remarkable thermal stability of Li3.75Si is in stark contrast to the long-observed metastability for electrochemically synthesized Li3.75Si. The carbon encapsulation of Li4.4Si has also been studied for its potential applications in LIBs.
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines , 1012 14th Street, Golden, Colorado 80401, United States.
authors.forename: Jacqueline E
authors.initials: JE
authors.lastname: Cloud
authors.forename: Yonglong
authors.initials: Y
authors.lastname: Wang
authors.forename: Xuemin
authors.initials: X
authors.lastname: Li
authors.forename: Tara S
authors.initials: TS
authors.lastname: Yoder
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yang
authors.forename: Yongan
authors.initials: Y
authors.lastname: Yang