Results for “Li7PS6” | Engineering Papers

DOE OSTI2020

Materials Data on Li7PS6 by Materials Project

Li7PS6 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are seven inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four S2- atoms to form LiS4 tetrahedra that share corners with two equivalent PS4 tetrahedra, corners with seven LiS4 tetrahedra, and edges with two LiS4 tetrahedra. There are a spread of Li–S bond distances ranging from 2.45–2.59 Å. In the second Li1+ site, Li1+ is bonded to four S2- atoms to form distorted LiS4 tetrahedra that share corners with two equivalent PS4 tetrahedra, corners with five LiS4 tetrahedra, and edges with three LiS4 tetrahedra. There are a spread of Li–S bond distances ranging from 2.41–2.67 Å. In the third Li1+ site, Li1+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Li–S bond distances ranging from 2.51–2.79 Å. In the fourth Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Li–S bond distances ranging from 2.39–3.08 Å. In the fifth Li1+ site, Li1+ is bonded to four S2- atoms to form LiS4 tetrahedra that share corners with two equivalent PS4 tetrahedra, corners with seven LiS4 tetrahedra, and edges with two LiS4 tetrahedra. There are a spread of Li–S bond distances ranging from 2.45–2.53 Å. In the sixth Li1+ site, Li1+ is bonded to four S2- atoms to form distorted LiS4 tetrahedra that share corners with two equivalent PS4 tetrahedra, corners with eight LiS4 tetrahedra, and edges with two LiS4 tetrahedra. There are a spread of Li–S bond distances ranging from 2.44–2.56 Å. In the seventh Li1+ site, Li1+ is bonded to four S2- atoms to form LiS4 tetrahedra that share corners with two equivalent PS4 tetrahedra, corners with five LiS4 tetrahedra, and edges with three LiS4 tetrahedra. There are a spread of Li–S bond distances ranging from 2.44–2.48 Å. P5+ is bonded to four S2- atoms to form PS4 tetrahedra that share corners with ten LiS4 tetrahedra. There are one shorter (2.05 Å) and three longer (2.06 Å) P–S bond lengths. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded to seven Li1+ atoms to form distorted SLi7 pentagonal bipyramids that share corners with two equivalent SLi7 pentagonal bipyramids, corners with three equivalent SLi3P tetrahedra, an edgeedge with one SLi7 pentagonal bipyramid, and a faceface with one SLi7 pentagonal bipyramid. In the second S2- site, S2- is bonded in a 4-coordinate geometry to four Li1+ and one P5+ atom. In the third S2- site, S2- is bonded to seven Li1+ atoms to form distorted SLi7 pentagonal bipyramids that share corners with two equivalent SLi7 pentagonal bipyramids, corners with three equivalent SLi3P tetrahedra, an edgeedge with one SLi7 pentagonal bipyramid, and a faceface with one SLi7 pentagonal bipyramid. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the fifth S2- site, S2- is bonded to three Li1+ and one P5+ atom to form corner-sharing SLi3P tetrahedra. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Wet chemical synthesis and properties of argyrodite sulfide solid electrolytes for solid state lithium batteries

The commercialization of the lithium-ion battery (LIB) in 1991 was responsible for the explosion in portable electronic technologies that has been seen over the past 30 years. With the advent of electric vehicles and other high-powered technologies, there is tremendous demand for LIBs with higher energy density and high safety. To achieve this, new electrode materials must be explored. The obvious choice of anode material would be pure metal lithium, which has a theoretical specific capacity of 3860 mAh g-1 . Unfortunately, metal lithium anodes have not been widely commercialized due to their tendency to react violently with the flammable liquid electrolytes used in today’s batteries. Battery safety can best be achieved by adopting solid electrolytes in place of liquid electrolytes. Solid electrolytes are nonvolatile and nonflammable, safely allowing for the combination of high-capacity cathode materials with a Li metal anode. Argyrodite sulfide solid electrolytes such as halogen-doped Li6PS5X (X = Cl, Br, I) are noted for their high ionic conductivity. But before sulfides can be commercially adopted, they possess several disadvantages which must be addressed, including time- and energy-consuming synthesis processes, poor electrochemical stability, and intrinsically poor air stability. This dissertation seeks to address each of these challenges through materials design an synthesis strategies. In this work, we pioneer a solvent-based approach for the synthesis of argyrodite solid electrolytes Li7PS6 and Li6PS5Xinstead of a stringent solid-state synthesis. Nontoxic ethanol is employed as the solvent, enabling a rapid synthetic approach to produce argyrodite solid electrolytes with high phase purity and compositional flexibility. Compared with Li7PS6, halogen doping (i.e. X = F, Cl, Br, I) not only increases the ionic conductivity, but also enhances the electrochemical stability at the interface towards Li metal. Specifically, F-doped argyrodites produce a robust SEI layer containing LiF, contributing to enhanced interfacial stability. Finally, to address the air instability challenge, argyrodite-incorporated composite solid electrolytes (CSEs) are designed and prepared to produce stable and flexible membranes that are demonstrated in solid-state Li metal batteries. These advances push argyrodite sulfide solid electrolyte research further and pave the way for the proliferation of next generation lithium metal batteries.

25 ENERGY STORAGE↗