Structural and electronic features of binary Li2S-P2S5 glasses

Abstract

The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li+ ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li+ ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes.

Pair distribution function analysis of sulfide glassy electrolytes for all-solid-state batteries: Understanding the improvement of ionic conductivity under annealing condition

“…On the basis of a previous study 10 , the first peak at around 2.0 Å is related to the P-S correlation associated with the PS 4 tetrahedral anions and has no dependence on the annealing treatment. This means that the PS 4 tetrahedral anions remain in the structure during the crystallization.…”

“…In general, the crystallization of glassy materials results in a decrease in the conductivity 9 , although it increases in a few sulfide glasses owing to the crystallization of a highly conductive new phase 2 . Recently, we reported that 75Li 2 S-25P 2 S 5 glass in the binary Li 2 S-P 2 S 5 system with strongly polarized sulfur has high ionic conductivity 10 . In the sulfide glasses as below reported here, an interesting improvement in the conductivity is observed during annealing, which appears in the glassy phase.…”

Correlating Macro and Atomic Structure with Elastic Properties and Ionic Transport of Glassy Li2S‐P2S5 (LPS) Solid Electrolyte for Solid‐State Li Metal Batteries

“…[ 24 ] From the spectra collected, it was observed that the sample hot‐pressed at 270 MPa, E of 28.0 ± 0.6 GPa, showed a ≈20% increase in peak intensity compared to the sample hot‐pressed at 47 and 90 MPa ( E of 16.7 ± 0.6 and 16.5 ± 0.5 GPa, respectively), mostly on the Li–S pairs. This increase is closely related to the change in the coordination environment of the Li ions, [ 25 ] but more importantly, suggesting a more interconnected arrangement between Li and S for the samples hot‐pressed at 180 and 270 MPa resulting in larger elastic constants.…”

Structure and Ionic Conductivity of Li2S–P2S5 Glass Electrolytes Simulated with First-Principles Molecular Dynamics

“…The calculated results were analyzed for trajectories by a DFT-MD simulation at 300 K using the ISAACS program (Le Roux and Petkov, 2010). We determined the experimental data based on the previous work of Ohara et al (2016). Whereas the calculated results show the fluctuations due to our limited sampling, the agreement between our results and the experimental data is good for large values of Q, and the agreement is still good for small values of Q with respect to the positions of maxima and minima.…”