Synthesis, structure, and conduction mechanism of the lithium superionic conductor Li10+δGe1+δP2−δS12Electronic supplementary information (ESI) available. CCDC 1027666. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4ta05231e

• Main Authors: Kwon, Ohmin, Hirayama, Masaaki, Suzuki, Kota, Kato, Yuki, Saito, Toshiya, Yonemura, Masao, Kamiyama, Takashi, Kanno, Ryoji
• Format: Journal Article
• Language: English
• Published: 02.12.2014
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c4ta05231e

A solid solution of the lithium superionic conductor Li 10+ δ Ge 1+ δ P 2− δ S 12 (0 ≤ δ ≤ 0.35) was synthesized and its structure and ionic conductivity were examined. The highest ionic conductivity value of 1.42 × 10 −2 S cm −1 was obtained at 300 K with a sintered pellet of the sample having the highest solid solution lithium content of δ = 0.35. The Arrhenius conductivity curves obtained for this material exhibited a gradual change in slope over the temperature range of 193-373 K and the activation energy for ionic conduction decreased from 26 kJ mol −1 below 373 K to 7 kJ mol −1 above 573 K, which is typical of highly ionic conducting solids. The crystal structures of the solid solutions were determined using neutron diffraction, and conduction pathways were visualized through analysis by applying the maximum entropy method. The lithium distribution was found to disperse significantly throughout a one-dimensional conduction pathway as the temperature was increased from 4.8 K to 750 K. In addition, two-dimensional distribution of lithium along the ab plane became apparent at high temperatures, suggesting that the conduction mechanism changes from one-dimensional to three-dimensional with increasing temperature. The lithium diffusion pathway in the LGPS structure visualized through MEM analysis assisted in elucidating the conductivity pathway changes with temperature.