Structural and electronic features of binary Li2S-P2S5 glasses

摘要

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 PS_x polyhedra decreases. It is conjectured that Li⁺ ions around the face of PS_x 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 PS_x and LiS_y 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.