Revealing the Ion Dynamics in Li10GeP2S12 by Quasi-Elastic Neutron Scattering Measurements

• Published in: Journal of physical chemistry. C 2022-06, Vol.126 (22), p.9518-9527
• Main Authors: Hori, Satoshi, Kanno, Ryoji, Kwon, Ohmin, Kato, Yuki, Yamada, Takeshi, Matsuura, Masato, Yonemura, Masao, Kamiyama, Takashi, Shibata, Kaoru, Kawakita, Yukinobu
• Format: Article
• Language: eng ; jpn
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.2c01748

Understanding Li-ion conduction in superionic conductors accelerates the development of new solid electrolytes to enhance the charge–discharge performances of all-solid-state batteries. We performed a quasi-elastic neutron scattering study on a model superionic conductor (Li10+x Ge1+x P2–x S12, LGPS), to reveal its ion dynamics on an angstrom-scale spatial range and a pico-to-nanosecond temporal range. The observation of spectra at 298 K confirmed the high lithium diffusivity. The obtained diffusion coefficient was in the order of 10–6 cm2 s–1 at temperatures >338 K and was higher than the reported diffusion coefficient over a longer time scale, as determined by the pulse-field gradient nuclear magnetic resonance method. This difference indicates that there are impediments to ionic motion over a longer time scale. The dynamic behavior of the Li ions was compared with that observed for the Li9P3S9O3 phase, which possesses the same crystal structure type, but a lower ionic conductivity. The LGPS phase possessed a high lithium mobility over a distance of ∼10 Å, as well as a larger fraction of mobile Li ions, thereby indicating that these features enhance lithium conduction over a longer spatial scale, which is important in all-solid-state batteries.