Issue 3, 2020

Ionic conduction mechanism of a lithium superionic argyrodite in the Li–Al–Si–S–O system

Abstract

We report the conduction mechanism in oxygen-substituted lithium conductors composed of the Li6.15Al0.15Si1.35S6−xOx (LASSO) system, which is a novel member of the argyrodite-type family and has superionic conductivities, making it suitable for all-solid-state batteries. The crystal structures, ionic conductivities, and electrochemical properties of these systems were examined using powder X-ray and neutron diffractometry combined with impedance spectroscopy and cyclic voltammetry measurements. The optimal Li6.15Al0.15Si1.35S5.4O0.6 (x = 0.6) material exhibited a high ionic conductivity of 1.24 mS cm−1 at 25 °C with a low activation energy of 36.6 kJ mol−1. Rietveld refinement and maximum-entropy-method analysis using neutron diffraction data revealed unique interstitial Li+ and O2−/S2− site disorder, which led to a flatter energy landscape for migrating Li+ ions and, thus, a low percolation threshold for three dimensional (3D) Li-ion diffusion. Oxygen substitution also stabilized the structure, and a wide electrochemical window from −0.1 V to 5 V vs. Li/Li+ was achieved. The significant improvements in the ionic conductivity and stability owing to structural changes after cation and anion substitutions reveal an important strategy toward the development of argyrodite-type superionic conductors.

Graphical abstract: Ionic conduction mechanism of a lithium superionic argyrodite in the Li–Al–Si–S–O system

Supplementary files

Article information

Article type
Paper
Submitted
22 mar 2020
Accepted
20 apr 2020
First published
22 apr 2020
This article is Open Access
Creative Commons BY-NC license

Mater. Adv., 2020,1, 334-340

Ionic conduction mechanism of a lithium superionic argyrodite in the Li–Al–Si–S–O system

W. Huang, L. Cheng, S. Hori, K. Suzuki, M. Yonemura, M. Hirayama and R. Kanno, Mater. Adv., 2020, 1, 334 DOI: 10.1039/D0MA00115E

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