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A Novel Phase of Li 15 Si 4 Synthesized under Pressure
Author(s) -
Zeng Zhidan,
Zeng Qingfeng,
Liu Nian,
Oganov Artem R.,
Zeng Qiaoshi,
Cui Yi,
Mao Wendy L.
Publication year - 2015
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201500214
Subject(s) - materials science , orthorhombic crystal system , lithium (medication) , phase (matter) , crystallography , silicon , crystal structure , coordination number , ab initio , ion , metallurgy , medicine , chemistry , physics , organic chemistry , quantum mechanics , endocrinology
Li 15 Si 4 , the only crystalline phase that forms during lithiation of the Si anode in lithium‐ion batteries, is found to undergo a structural transition to a new phase at 7 GPa. Despite the large unit cell of Li 15 Si 4 (152 atoms in the unit cell), ab initio evolutionary metadynamics (using the USPEX code) successfully predicts the atomic structure of this new phase (β‐Li 15 Si 4 ), which has an orthorhombic structure with an Fdd2 space group. In the new β‐Li 15 Si 4 phase Si atoms are isolated by Li atoms analogous to the original cubic phase (α‐Li 15 Si 4 ), whereas the atomic packing is more efficient owing to the higher SiLi coordination number and shorter SiLi, LiLi bonds. β‐Li 15 Si 4 has substantially larger elastic moduli compared with α‐Li 15 Si 4 , and has a good electrical conductivity. As a result, β‐Li 15 Si 4 has superior resistance to deformation and fracture under stress. The theoretical volume expansion of Si would decrease 25% if it transforms to β‐Li 15 Si 4 , instead of α‐Li 15 Si 4 , during lithiation. Moreover, β‐Li 15 Si 4 can be recovered back to ambient pressure, providing opportunities to further investigate its properties and potential applications.