Construction and dynamic property of the lithium in conductor having rock salt structure

Li_3InBr_6是制造全固态锂离子电池最有前途的化合物之一。该化合物经历了一个具有岩盐结构的超离子相的相变，电导率高达2^*10^<-2>Scm，正好高于超离子相变。为了理解这种高导电性，我们首先尝试合成一系列类似的化合物，并寻找新的超离子导体。其次，我们用各种测量方法讨论了传导机理。从这些实验中可以看出以下几点：In^<3+>的离子半径与Li^+非常相似。这一事实对于LiX-InX_3体系中超离子相的出现是最重要的。Na_3InCl_6不像Li_3InBr_6表现出高导电性。然而，我们可以通过x射线衍射和核磁共振成像来确定Na^+的传导路径。超离子相Li_3InBr_6与Li_3InCl_6同构，其中Li^+和in ^<3+>均为无序态。^7LiNMR表明，大约15%的Li^+对相变以上的电导率有贡献。随着温度的升高，x射线衍射图逐渐转变为具有岩盐结构特征的简单衍射图。这表明平均结构的出现是快速阳离子扩散的结果。

Li_3InBr_6 is one of the promising compounds for the construction of an all solid-state lithium ion battery. This compound undergoes a phase transition to a superionic phase having rock-salt structure and the conductivity is as high as 2^*10^<-2>Scm just above the superionic phase transition. In order to understand this high conductivity, firstly we tried to synthesize a series of similar compounds and searched new superionic conductors. Secondary we discussed the conduction mechanism by means of various measurements. Following points have become apparent from these experiments.1.The ionic radius of In^<3+> is quite similar to that of Li^+. This fact is most important for the appearance of the superionic phase in the LiX-InX_3 system.2.Na_3InCl_6 did not show high conductivity like Li_3InBr_6. However, we could determine the conduction path of the Na^+ by means of X-ray diffraction and NMR.3.Li_3InBr_6 at the superionic phase was isomorphous with Li_3InCl_6, in which not only Li^+ but In^<3+> are disordered state.4.^7LiNMR suggested that ca 15% of the Li^+ contributed to the conductivity just above the phase transition.5.With increasing temperature the X-ray diffraction pattern changed gradually to a simple one which was characteristic to a rock salt structure. This suggests the appearance of the averaged structure as a result of the rapid cationic diffusion.