Local Structure of Lithium Ion Conducting Germanium Sulfide Glass: (Li₂S)₄₀(GeS₂)₆₀

Abstract

The electrochemical and structural properties of (Li 2 S) 40 (GeS 2 ) 60 glass synthesized by mechanical alloying were studied using ac impedance, time-of-flight neutron diffraction (TOF-ND), and synchrotron X-ray diffraction (SXRD). The electrical conductivity was 3.4 × 10 −6 S/cm at room temperature. The three-dimensional structure obtained by the reverse Monte Carlo modeling clearly indicated the network configuration of corner-sharing GeS 4 tetrahedra together with Li ions. The coordination number of S atoms around a Li atom, N Li-S , assessed within r = 3.3 Å, shows that LiS 4 units occupied 25% of all LiS n units, LiS 5 units occupied 16%, and LiS 3 units occupied 14%. The results indicate that Li ions prefer to be located in the space surrounded by S atoms in (Li 2 S) 40 (GeS 2 ) 60 glass.

Pockets, jumps and filaments: classifying ionic motion and determining the role of structure in electrochemical properties of 2Li2S-GeS2 superionic glasses

“…Here, we have investigated from density function theory based MD the structural, dynamic and electric properties of amorphous and liquid GeS 2 -2Li 2 S (L2G) which has been recognized as an interesting electrolyte material because rather large conductivities can be obtained (about 10 −4 − 10 −3 Ω −1 •cm −1 ), and used in future all-solid-state battery applications. After the seminal contributions of Ribes and co-workers [19,20] in the mid 1980's, such glasses have received renewed interest [29][30][31]82] so that contributions from numerical simulations are now timely as they can provide a detailed description of the atomic structure, prior to the establishment of structure-property relationships. These might help in investigating more complex materials [88] such as Li 10 GeP 2 S 12 which uses a combination of GeS 2 and P 2 S 5 networks.…”

“…This level of conductivity makes the present Li-based thiogermanate glasses very attractive for possible applications, and recent measurements on multicomponent electrolytes have suggested, indeed, that the Li 2 S-GeS 2 system can be used as base material for a massive improvement of Li-ion conductivity [26,27]. More recently, neutron and x-ray diffraction (XRD) studies have been performed over almost the same range of composition in these thiogermanate glasses [28][29][30], and they have permitted to validate three-dimensional structure models by using Reverse Monte Carlo [31] (RMC) and molecular dynamics (MD) simulation techniques [29] at low temperature where activation barriers for structural relaxation are notoriously large. Such models reveal that the base network features (i.e.…”