Lithium ion conductivity of halides with a defect spinel structure

离子电导率是材料的功能特性之一。制备具有高离子电导率的新型材料是燃料电池或二次电池发展的关键技术。本研究制备了LiInBr_4和Li_3InBr_6型固体电解质，并利用高分辨率x射线衍射和固体核磁共振对其结构和导电机理进行了研究。这两种结构都可视为岩盐类型，其中三个Li^+被一个in ^<3+>和两个空位所取代。立方LiInBr_4虽然属于缺陷尖晶石结构，但由于四面体位置为空，其结构可视为缺陷岩盐型。由于In^<3+>的位置无序在超离子状态下普遍存在，这种无序对Li^+的传导起着重要的作用。在x<0.2以下，LiBr和InBr_3之间存在Li_<1-x>,In_<x/3>Br的连续固溶体。

Ionic conductivity is one of the functional properties of material. The preparation of the new materials having high ionic conductivity is a key technology for the development of fuel cell or secondary battery. In this research, solid electrolytes having the formula LiInBr_4 and Li_3InBr_6 were prepared and their structures and conduction mechanisms were investigated on the basis of high resolution X-ray diffraction and solid state NMR.Both of these structures could be regarded as a rock salt type in which three Li^+ is replaced by one In^<3+> and two vacancies. Although cubic LiInBr_4 belongs to a defect spinel structure, its structure can be regarded as a defect rock salt type because tetrahedral site is empty. Since the positional disorder of In^<3+> was commonly observed at the superionic state, this disorder plays an important role for the Li^+ conduction. Furthermore, a continuous solid solution Li_<1-x>,In_<x/3>Br, between LiBr and InBr_3 was suggested at least below x<0.2.