Effect of pressure on transport properties of granular lithium ion conductors

TP的一个中心问题是合成新的无定形含锂固体，并研究高压高温处理后锂迁移率的变化。该项目的一个主要目标是通过实验确定传输性能和以下参数之间的关系：-组合物和结构类型-有序状态-压实度-锂的局部环境在第一阶段，我们专注于合成，压实和表征系统Li 2 O-Al 2 O3-SiO2中的无定形化合物。使用阻抗谱和NMR测定锂迁移率。根据这种方法，我们想研究在压力/温度处理非晶粉末过程中，组分、结构状态和颗粒尺寸对所选体系中锂输运的影响。我们选择两个代表更多离子的模型系统（例如，LiTaO 3和LiNbO 3）和更共价的材料（例如，LiFePO 4或LiMgPO 4，后者具有Mg具有单一氧化态的优点）。该项目的目的是分离体积和晶界扩散对颗粒单相系统中Li输运的影响，并研究压实过程中这些输运性质的变化。为此，我们希望应用在项目第一阶段开发的新活塞缸装置。该方法允许直接测量的阻抗谱和体积的变化，在压实过程中的温度和压力的函数。使用具有受控湿度和氧分压的气氛，可以在开始压缩之前在运行温度下预调节粉末。我们特别期望H2O对压实动力学具有重大影响，进而对锂的流动性具有重大影响。微观分析和光谱学方法将使人们了解压实后的结构和拓扑修饰。核磁共振测量，如果可能的话，机械弛豫光谱将提供有关锂在起始材料和实验后样品中的迁移率的信息。

A central issue of TP is the synthesis of new amorphous Li-bearing solids and the investigation of the change in lithium mobility upon high pressure - high temperature treatment. A primary goal of the project is to determine experimentally the relationships between transport properties and the following parameters: - composition and structure type - state of ordering - degree of compaction - local environment of lithium In the first period we have focussed on the synthesis, compaction and characterization of amorphous compounds in the system Li2O-Al2O3-SiO2. Lithium mobility was determined using impedance spectroscopy and NMR. Following this approach we want to study the influence of composition structural state and particle size on the transport of lithium for selected systems in situ during pressure/temperature treatment of amorphous powders. We choose two model systems representing more ionic (e.g., LiTaO3 und LiNbO3) and more covalent materials (e.g., LiFePO4 or LiMgPO4, the latter one has the advantage that Mg has a single oxidation state), respectively. The aim of the project is to separate effects of volume and grain boundary diffusion on Li-transport in granular single phase systems and to investigate the change of theses transport properties during compaction. For doing so, we want to apply the new piston cylinder apparatus which was developed during the first period of the project. The method allows direct measurement of impedance spectra and volume changes during compaction in function of temperature and pressure. Using an atmosphere with controlled humidity and oxygen partial pressure, the powders can be pre-conditioned at run temperature before starting compression. We expect in particular that H2O has major impact on compaction kinetics and in turn on lithium mobility. Microanalytical and spectroscopic methods will give insights to structural and topological modifications upon compaction. NMR measurements and, if possible, mechanical relaxation spectroscopy will provide information about lithium mobility in starting materials and post-experimental samples.