Revealing the ion dynamics in Li
GeP
S
by quasi-elastic neutron scattering measurements
Hori, Satoshi*; Kanno, Ryoji*; Kwon, O.*; Kato, Yuki*; Yamada, Takeshi*; Matsuura, Masato*; Yonemura, Masao*; Kamiyama, Takashi*; Shibata, Kaoru
; Kawakita, Yukinobu

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 (Li
Ge
P
S
, 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
cm
s
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 Li
P
S
O
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.