Li+ ionic conductivities and diffusion mechanisms in Li-based imides and lithium amide
Li+ ionic conductivities and diffusion mechanisms in Li-based imides and lithium amide
复制标题
DOI：
10.1039/c2cp23636b
复制
发表时间：
2012-01-01
影响因子：
3.3
通讯作者：
Chen, Ping
中科院分区：
文献类型：
--
作者：
Li, Wen;Wu, Guotao;Chen, Ping
本文采用离子电导率测量和第一性原理模拟方法研究了锂基酰亚胺（Li 2NH，Li 2 Mg（NH）（2）和Li 2Ca（NH）（2））和氨基锂（LiNH 2）中Li+离子的扩散性质。实验结果表明，室温下Li+离子在Li_2NH（2.54 × 10 ~（-4）S cm ~（-1））和Li_2Ca（NH）（2）（6.40 × 10 ~（-6）S cm ~（-1））中表现出超离子导电性，而Li+离子在Li_2Mg（NH）（2）和LiNH_2中几乎不导电.模拟结果表明，Li+离子在Li 2NH中的扩散可能是由Frenkel对缺陷或带电空位介导的，扩散途径更可能是通过沿着[001]方向在八面体和四面体之间的一系列中间跳跃.计算的Li+离子在Li 2NH中的导电活化能和指前因子与实验测定值具有很好的可比性，表明实验和理论研究的一致性。LiNH 2中的缺陷形成能的计算表明，Li缺陷难以产生以介导Li+离子扩散，导致室温下LiNH 2中Li+离子导电性差。
In this study, both experimental ionic conductivity measurements and the first-principles simulations are employed to investigate the Li+ ionic diffusion properties in lithium-based imides (Li2NH, Li2Mg(NH)(2) and Li2Ca(NH)(2)) and lithium amide (LiNH2). The experimental results show that Li+ ions present superionic conductivity in Li2NH (2.54 x 10(-4) S cm(-1)) and moderate ionic conductivity in Li2Ca(NH)(2) (6.40 x 10(-6) S cm(-1)) at room temperature; while conduction of Li+ ions is hardly detectable in Li2Mg(NH)(2) and LiNH2 at room temperature. The simulation results indicate that Li+ ion diffusion in Li2NH may be mediated by Frenkel pair defects or charged vacancies, and the diffusion pathway is more likely via a series of intermediate jumps between octahedral and tetrahedral sites along the [001] direction. The calculated activation energy and pre-exponential factor for Li+ ion conduction in Li2NH are well comparable with the experimentally determined values, showing the consistency of experimental and theoretical investigations. The calculation of the defect formation energy in LiNH2 reveals that Li defects are difficult to create to mediate the Li+ ion diffusion, resulting in the poor Li+ ion conduction in LiNH2 at room temperature.