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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Improving Interface Stability of Si Anodes by Mg Coating in Li-Ion Batteries

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries (LIBs), but its short calendar life and poor cycling performance prevent its large-scale adoption. Introducing magnesium (Mg) salt into the electrolyte has been recently shown to form a ternary Li–Mg–Si Zintl phase upon lithiation of Si and improve the cycling performance. However, the ternary Zintl phase formation mechanism and its impact on the solid electrolyte interphase (SEI) are not yet well understood. In this work, we demonstrate the formation of a ternary Li–Mg–Si Zintl phase by Mg coating of the Si anode, where Mg diffuses into the Si film upon deposition and intermixes further during the lithiation process. The presence of the Zintl phase improves the interface stability, alters the nature of the SEI, and enhances the cycling performance of the Si anode. This study provides insights into the formation mechanism of the ternary Zintl phase and guidelines for the future design of Si anodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on Li2MgSi by Materials Project

Li2MgSi crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of eight lithium molecules and one Li7(MgSi)4 framework. In the Li7(MgSi)4 framework, there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four Si4- atoms to form distorted LiSi4 tetrahedra that share corners with six equivalent MgSi4 tetrahedra, corners with ten equivalent LiSi4 tetrahedra, edges with three equivalent LiSi4 tetrahedra, and edges with three equivalent MgSi4 tetrahedra. There are three shorter (2.75 Å) and one longer (2.77 Å) Li–Si bond lengths. In the second Li1+ site, Li1+ is bonded in a distorted single-bond geometry to one Si4- atom. The Li–Si bond length is 2.78 Å. Mg2+ is bonded to four Si4- atoms to form MgSi4 tetrahedra that share corners with six equivalent LiSi4 tetrahedra, corners with ten equivalent MgSi4 tetrahedra, edges with three equivalent LiSi4 tetrahedra, and edges with three equivalent MgSi4 tetrahedra. There are three shorter (2.75 Å) and one longer (2.77 Å) Mg–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a body-centered cubic geometry to eight equivalent Mg2+ atoms. In the second Si4- site, Si4- is bonded in a body-centered cubic geometry to four equivalent Li1+ and four equivalent Mg2+ atoms. In the third Si4- site, Si4- is bonded in a 8-coordinate geometry to fourteen Li1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li12Mg3Si4 by Materials Project

Li12Mg3Si4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Li is bonded in a 10-coordinate geometry to two equivalent Mg and three equivalent Si atoms. There are one shorter (2.79 Å) and one longer (2.80 Å) Li–Mg bond lengths. There are a spread of Li–Si bond distances ranging from 2.66–2.78 Å. Mg is bonded to eight equivalent Li and four equivalent Si atoms to form MgLi8Si4 cuboctahedra that share corners with eight equivalent SiLi9Mg3 cuboctahedra, edges with eight equivalent MgLi8Si4 cuboctahedra, and faces with four equivalent SiLi9Mg3 cuboctahedra. All Mg–Si bond lengths are 2.89 Å. Si is bonded to nine equivalent Li and three equivalent Mg atoms to form distorted SiLi9Mg3 cuboctahedra that share corners with six equivalent MgLi8Si4 cuboctahedra, edges with six equivalent SiLi9Mg3 cuboctahedra, faces with three equivalent MgLi8Si4 cuboctahedra, and faces with five equivalent SiLi9Mg3 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2MgSi by Materials Project

Li2MgSi is alpha bismuth trifluoride-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional and consists of four lithium molecules and one LiMgSi framework. In the LiMgSi framework, Li1+ is bonded to four equivalent Si4- atoms to form LiSi4 tetrahedra that share corners with four equivalent MgSi4 tetrahedra, corners with twelve equivalent LiSi4 tetrahedra, and edges with six equivalent MgSi4 tetrahedra. All Li–Si bond lengths are 2.76 Å. Mg2+ is bonded to four equivalent Si4- atoms to form MgSi4 tetrahedra that share corners with four equivalent LiSi4 tetrahedra, corners with twelve equivalent MgSi4 tetrahedra, and edges with six equivalent LiSi4 tetrahedra. All Mg–Si bond lengths are 2.76 Å. Si4- is bonded in a body-centered cubic geometry to four equivalent Li1+ and four equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(Mg2Si)2 by Materials Project

Li(Mg2Si)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. All Li–Mg bond lengths are 2.84 Å. Mg is bonded in a 6-coordinate geometry to two equivalent Li and four Si atoms. There are two shorter (2.77 Å) and two longer (2.84 Å) Mg–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. In the second Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2MgSi by Materials Project

Li2MgSi crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four equivalent Li1+ and four equivalent Si4- atoms to form distorted LiLi4Si4 tetrahedra that share corners with sixteen MgSi4 tetrahedra and edges with six equivalent LiSi4 tetrahedra. All Li–Li bond lengths are 2.51 Å. All Li–Si bond lengths are 2.73 Å. In the second Li1+ site, Li1+ is bonded to four equivalent Si4- atoms to form LiSi4 tetrahedra that share corners with eight equivalent LiSi4 tetrahedra, corners with eight MgSi4 tetrahedra, edges with two equivalent LiLi4Si4 tetrahedra, and edges with four equivalent MgSi4 tetrahedra. All Li–Si bond lengths are 2.75 Å. In the third Li1+ site, Li1+ is bonded in a 4-coordinate geometry to one Li1+ and three equivalent Si4- atoms. All Li–Si bond lengths are 3.03 Å. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four equivalent Si4- atoms to form MgSi4 tetrahedra that share corners with sixteen LiLi4Si4 tetrahedra and edges with six equivalent MgSi4 tetrahedra. All Mg–Si bond lengths are 2.78 Å. In the second Mg2+ site, Mg2+ is bonded to four equivalent Si4- atoms to form MgSi4 tetrahedra that share corners with eight LiLi4Si4 tetrahedra, corners with eight equivalent MgSi4 tetrahedra, edges with two equivalent MgSi4 tetrahedra, and edges with four equivalent LiSi4 tetrahedra. All Mg–Si bond lengths are 2.77 Å. Si4- is bonded in a distorted body-centered cubic geometry to seven Li1+ and four Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiMg2Si by Materials Project

LiMg2Si is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. All Li–Mg bond lengths are 2.87 Å. Mg is bonded in a body-centered cubic geometry to four equivalent Li and four equivalent Si atoms. All Mg–Si bond lengths are 2.87 Å. Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3(Mg2Si)4 by Materials Project

Li3(Mg2Si)4 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. All Li–Mg bond lengths are 2.86 Å. Mg is bonded in a 7-coordinate geometry to three equivalent Li and four Si atoms. There are three shorter (2.83 Å) and one longer (2.89 Å) Mg–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. In the second Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li14MgSi4 by Materials Project

Li14MgSi4 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. there are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent Si4- atoms. There are a spread of Li–Si bond distances ranging from 2.62–2.80 Å. In the second Li1+ site, Li1+ is bonded in a distorted trigonal planar geometry to three equivalent Si4- atoms. There are one shorter (2.63 Å) and two longer (2.76 Å) Li–Si bond lengths. In the third Li1+ site, Li1+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent Si4- atoms. There are a spread of Li–Si bond distances ranging from 2.61–2.81 Å. In the fourth Li1+ site, Li1+ is bonded to four equivalent Si4- atoms to form LiSi4 tetrahedra that share corners with four equivalent LiSi4 tetrahedra and corners with four equivalent MgSi4 tetrahedra. There are two shorter (2.88 Å) and two longer (2.90 Å) Li–Si bond lengths. Mg2+ is bonded to four equivalent Si4- atoms to form MgSi4 tetrahedra that share corners with eight equivalent LiSi4 tetrahedra. All Mg–Si bond lengths are 2.85 Å. Si4- is bonded to eleven Li1+ and one Mg2+ atom to form a mixture of distorted edge and face-sharing SiLi11Mg cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(Mg2Si)4 by Materials Project

Li(Mg2Si)4 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. All Li–Mg bond lengths are 2.84 Å. Mg is bonded in a 5-coordinate geometry to one Li and four Si atoms. There are one shorter (2.72 Å) and three longer (2.80 Å) Mg–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms. In the second Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Mg atoms.

36 MATERIALS SCIENCE↗