Phase stability of alloy-type lithium storage anode materials

在目前的项目中，将进行系统的研究，为锂电池中锂存储阳极的潜在合金系统提供连贯和广泛的信息。三个项目合作伙伴将calphhad方法的理论能力，纳米材料的热力学以及相变过程中热力学和动力学的结合，以及热力学性质测量，纳米材料生产和纳米结构表征的实验能力结合起来。采用calphhad方法研究Li-Si- sn - c四元合金体系及其各自的子系统Li-Si， Li-Sn， Li-Si- c和Li-Sn- c。由于纳米结构通常被认为是提高锂电池循环稳定性的一种策略，因此晶粒和相边界对合金系统相稳定性的贡献将基于多余自由能作为结构长度尺度的函数进行建模。在实验方面，选定的合金将在SPS系统中通过粉碎、球磨和随后的烧结制成铸锭和纳米结构。纳米结构将在基本上无氧的封闭系统中使用独特的实验设备进行。纳米结构材料将被彻底表征。重点是在透射电子显微镜（TEM）下确定晶粒尺寸分布、相分布和取向分布。为此，现有的TEM分析方法将进一步发展并扩展到超细晶粒尺寸。通过相图、综合热力学描述和本项目开发的工具，可以对上述合金系统中的大范围成分进行循环稳定性估计和锂存储容量预测，并将确定有前途的锂电池合金材料。

In the present project, a systematic study will be carried out that provides coherent and extensive information about potential alloy systems for Li storage anodes in Li batteries. Three project partners combine theoretical competences in the Calphad method, the thermodynamics of nanomaterials and the combination of thermodynamics and kinetics during phase transformations, as well as experimental competences in the measurement of thermodynamic properties, production of nanomaterials and characterization of nanoscaled structures.The quaternary alloy system Li-Si-Sn-C with the respective subsystems Li-Si, Li-Sn, Li-Si-C and Li-Sn-C will be investigated/established using the Calphad method. Since nanostructuring is generally accepted as a strategy to achieve an increased cycling stability in Li batteries, the contribution of grain and phase boundaries to the phase stability in the alloy systems will be modeled on the basis of excess free energies as a function of structural length scales.On the experimental side, selected alloys will be cast as ingots and nanostructured by crushing, ball-milling and subsequent sintering in an SPS system. Nanostructuring will be carried out using unique experimental equipment in a closed system with essentially oxygenfree atmosphere. The nanostructured material will be thoroughly characterized. Focus will be to determine grain size distribution, phase distribution and orientation distribution in the Transmission Electron Microscope (TEM). For this, current TEM analysis methods will be further developed and extended to ultra fine grain sizes.With the phase diagrams, the comprehensive thermodynamic description and the tools developed in this project, an estimation of cycling stability and the prediction of Li storage capacity will be possible for a large range of compositions in the above mentioned alloy system, and promising materials for Li battery alloys will be identified.