期刊
ACS NANO
卷 7, 期 7, 页码 6303-6309出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn402349j
关键词
Si; lithiation; in situ TEM; EELS; phase transition; electronic structure
类别
资金
- U.S. Department of Energy (DOE) [DE-AC05-76RLO1830]
- DOE's Office of Biological and Environmental Research
- NSF [DMR-1006069]
Silicon has been widely explored as an anode material for lithium ion battery. Upon lithiation, silicon transforms to amorphous LixSi (a-LixSi) via electrochemical-driven solid-state amorphization. With increasing lithium concentration, a-LixSi transforms to crystalline Li15Si4 (c-Li15Si4). The mechanism of this crystallization process is not known. In this paper, we report the fundamental characteristics of the phase transition of alpha-LixSi to c-Li15Si4 using in situ scanning transmission electron microscopy, electron energy loss spectroscopy, and density function theory (DFT) calculation. We find that when the lithium concentration in a-LixSi reaches a critical value of x = 3.75, the a-Li3.75Si spontaneously and congruently transforms to c-Li15Si4 by a process that is solely controlled by the lithium concentration in the a-LixSi, involving neither large-scale atomic migration nor phase separation. DFT calculations Indicate that c-Li15Si4 formation is favored over other possible crystalline phases due to the similarity in electronic structure with a-Li3.75Si.
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