Elastic Properties, Defect Thermodynamics, Electrochemical Window, Phase Stability, and Li(+) Mobility of Li3PS4: Insights from First-Principles Calculations

Yanhan Yang; Qu Wu; Yanhua Cui; Yongchang Chen; Siqi Shi; Ru-Zhi Wang; Hui Yan

doi:10.1021/acsami.6b06754

Elastic Properties, Defect Thermodynamics, Electrochemical Window, Phase Stability, and Li(+) Mobility of Li3PS4: Insights from First-Principles Calculations

ACS Appl Mater Interfaces. 2016 Sep 28;8(38):25229-42. doi: 10.1021/acsami.6b06754. Epub 2016 Sep 15.

Authors

Yanhan Yang^{1

2}, Qu Wu², Yanhua Cui³, Yongchang Chen⁴, Siqi Shi², Ru-Zhi Wang¹, Hui Yan¹

Affiliations

¹ College of Materials Science and Engineering, Beijing University of Technology , Beijing 100124, China.
² School of Materials Science and Engineering, Shanghai University , Shanghai 200444, China.
³ Institute of Electronic Engineering, China Academy of Engineering Physics , Mianyang 621000, China.
⁴ Nanchang Hangkong University , Nanchang 330063, China.

PMID: 27588896
DOI: 10.1021/acsami.6b06754

Abstract

The improved ionic conductivity (1.64 × 10(-4) S cm(-1) at room temperature) and excellent electrochemical stability of nanoporous β-Li3PS4 make it one of the promising candidates for rechargeable all-solid-state lithium-ion battery electrolytes. Here, elastic properties, defect thermodynamics, phase diagram, and Li(+) migration mechanism of Li3PS4 (both γ and β phases) are examined via the first-principles calculations. Results indicate that both γ- and β-Li3PS4 phases are ductile while γ-Li3PS4 is harder under volume change and shear stress than β-Li3PS4. The electrochemical window of Li3PS4 ranges from 0.6 to 3.7 V, and thus the experimentally excellent stability (>5 V) is proposed due to the passivation phenomenon. The dominant diffusion carrier type in Li3PS4 is identified over its electrochemical window. In γ-Li3PS4 the direct-hopping of Lii(+) along the [001] is energetically more favorable than other diffusion processes, whereas in β-Li3PS4 the knock-off diffusion of Lii(+) along the [010] has the lowest migration barrier. The ionic conductivity is evaluated from the concentration and the mobility calculations using the Nernst-Einstein relationship and compared with the available experimental results. According to our calculated results, the Li(+) prefers to transport along the [010] direction. It is suggested that the enhanced ionic conductivity in nanostructured β-Li3PS4 is due to the larger possibility of contiguous (010) planes provided by larger nanoporous β-Li3PS4 particles. By a series of motivated and closely linked calculations, we try to provide a portable method, by which researchers could gain insights into the physicochemical properties of solid electrolyte.

Keywords: Li3PS4; defect chemistry; electrochemical window; ion diffusion mechanism; superionic conductor.