Revealing the ion dynamics in LiGePS by quasi-elastic neutron scattering measurements

堀 智*; 菅野 了次*; Kwon, O.*; 加藤 祐樹*; 山田 武*; 松浦 直人*; 米村 雅雄*; 神山 崇*; 柴田 薫; 川北 至信

Journal of Physical Chemistry C, 126(22), p.9518 - 9527, 2022/06

https://doi.org/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 (LiGePS, 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 cms 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 LiPSO 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 , 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-solidstate batteries.