Li+ diffusion mechanism in solid-state superionic conductors by QENS

Li7-xLa3Zr2-xAxO12 (A=Al, Ga, Nb, Ta; LLZO) is one of the premier electrolyte materials for all solid-state batteries, combining high ionic conductivity, good chemical stability, and a wide electrochemical window. To these days, a conclusive description of the lithium diffusion mechanism that leads to the high conductivity is absent in the literature, with the role of collective motions and ion correlation not fully investigated. We have recently begun a systematic study of LLZO with A = Nb and x = 0.5 to fully elucidate its structure and dynamics, aiming to fill this knowledge gap by focusing our attention on the role of collective motions and phonons in the diffusion. We have so far carried out inelastic neutron scattering measurements of the phonons using the MERLIN and MARI instruments, as well as a preliminary polarized QENS experiment on LET instrument a using powder sample with a slightly different composition. Now we wish to better understand the effect of temperature on the quasi-elastic diffuse scattering by performing a Rapid access measurement on powder sample of LLZO;Nb 0.5 on the IRIS instrument. We have prepared a large (20g) powder sample, and plan to measure the system at approximately 4 temperatures for 16 hours each.

Li₇₋ₓLa₃Zr₂₋ₓAₓO₁₂（其中A=Al、Ga、Nb、Ta，简称LLZO）是全固态电池的顶级电解质材料之一，兼具高离子电导率、优异化学稳定性与宽电化学窗口。时至今日，学界尚未对其高离子电导率背后的锂扩散机制给出定论性描述，集体运动与离子关联的作用仍未得到充分研究。我们近期启动了针对A=Nb且x=0.5的LLZO的系统性研究，旨在通过聚焦集体运动与声子在扩散过程中的作用填补这一认知空白，以全面阐明其结构与动力学特性。目前我们已利用MERLIN与MARI仪器完成了声子的非弹性中子散射测量，同时还使用LET仪器对成分略有差异的粉末样品开展了初步偏振准弹性中子散射（Quasi-Elastic Neutron Scattering, QENS）实验。如今我们希望通过在IRIS仪器上对LLZO;Nb 0.5粉末样品开展快速准入测量，进一步明晰温度对准弹性漫散射的影响。我们已制备了总量为20g的粉末样品，并计划在约4个温度点分别进行16小时的测量。