Hayamizu Kikuko, Seki Shiro, Haishi Tomoyuki
Institute of Applied Physics, University of Tsukuba, Tennodai, Tsukuba 305-8573, Japan.
Material Science Laboratory, Central Research Institute of Electric Power Industry, Nagasaka, Yokosuka 240-0196, Japan.
J Chem Phys. 2017 Jan 14;146(2):024701. doi: 10.1063/1.4973827.
Mobile lithium ions in a cubic garnet LiLaZrO (Al-stabilized) were studied using Li NMR spectroscopy for membrane and powder samples, the latter of which was ground from the membrane. Lithium diffusion in a micrometer space was measured using the pulsed-gradient spin-echo Li NMR method between 70 and 130 °C. When the observation time (Δ) was shorter than 20 ms, the echo attenuation showed diffusive diffraction patterns, indicating that the Li diffusing space is not free but restricted. For longer Δ, the values of apparent diffusion constant (D) became gradually smaller to approach an equilibrated value (close to a tracer diffusion constant). In addition, the D depends on the pulse field gradient strength (g) and became smaller as g became larger. These experimental results suggest that the lithium ions diffuse through Li pathways surrounded by stationary anions and lithium ions, and are affected by collisions and diffractions. One-dimensional profiles of the membrane sample of thickness 0.5 mm were observed from 65 to 110 °C and the area intensity, as well as the lithium occurrence near the surface, increased with the increase in temperature. The temperature-dependent area intensity showed a correspondence to the number of Li carrier ions estimated from the ionic conductivity and the equilibrated diffusion constant through the Nernst-Einstein relationship.
使用锂核磁共振光谱法对立方石榴石LiLaZrO（铝稳定）中的移动锂离子进行了研究，研究对象为膜样品和粉末样品，粉末样品由膜研磨而成。在70至130°C之间，使用脉冲梯度自旋回波锂核磁共振方法测量了微米空间中的锂扩散。当观测时间（Δ）短于20毫秒时，回波衰减呈现出扩散衍射图样，这表明锂的扩散空间并非自由空间而是受限空间。对于更长的Δ，表观扩散常数（D）的值逐渐变小，趋近于一个平衡值（接近示踪扩散常数）。此外，D取决于脉冲场梯度强度（g），且随着g的增大而变小。这些实验结果表明，锂离子通过由固定阴离子和锂离子包围的锂通道扩散，并受到碰撞和衍射的影响。在65至110°C范围内观察了厚度为0.5毫米的膜样品的一维轮廓，面积强度以及表面附近的锂含量随温度升高而增加。与温度相关的面积强度与通过能斯特-爱因斯坦关系从离子电导率和平衡扩散常数估算出的锂载流子离子数量相对应。
