Spatially resolved modeling and characterization of (de-)intercalation in Li-Ion battery materials

锂离子电池材料在充放电过程中会发生显著的体积变化，这取决于材料，与电子结构的变化有关。这会导致机械疲劳，从而降低电池的性能。该项目旨在通过理论和实验方法研究空间和时间分辨的Li分布和放电过程中相变的演变。该项目将专注于Li-Fe-P-O作为未来低成本电极材料的有前途的类别1。理论部分采用从头算方法计算了Li-Fe-P-O体系的结构稳定性和扩散系数，并采用相场法模拟了阳极-电解质界面的电荷转移、互扩散过程中的体积膨胀、相变和机械应力。通过将微结构元件收缩到纳米范围而获得的可能的器件改进将被包括表面和界面相关的材料特性所覆盖。实验部分包括在Li-Fe-P-O体系框架下组合制备正极材料薄膜样品及其高通量表征。将在手套箱中使用新模式的扫描电化学显微镜（SECM）研究样品在不同电解质中充电（放电）期间的Li分布。此外，将在手套箱中进行基于涂覆有锂电池材料的微加工电极的电化学/机械结合实验，以揭示Li（脱）嵌过程中的应力效应。该项目预计将首次提供一个完整的空间解析图像，以了解锂在纳米颗粒电池材料中的传输和相变的复杂机制。从理论和combinatorialinvestigations的路线，以改善材料将被查明。

Li-ion battery materials undergo a significant volume change during charging anddischarging, which is, dependent on the material, connected to a change of thecrystallographic structure. This causes mechanical fatigue which deteriorates the performanceof the batteries. The project aims on investigating, spatially- and time-resolved, the evolutionof the Li distribution and phase transitions during (dis-)charging by means of theoretical andexperimental methods. The project will focus on Li-Fe-P-O as a promising class for futurelow-cost electrode materials1. The theoretical part uses ab-initio calculations of structuralstability and diffusion coefficients in Li-Fe-P-O systems as well as phase-field simulation ofcharge transfer at the anode-electrolyte interface, volume expansion during interdiffusion,phase transformation and mechanical stress. The possible device improvement gained byshrinking microstructural elements to the nanometer regime will be covered by includingsurface and interface related materials characteristics. The experimental part consists ofcombinatorial preparation of thin film samples of cathode materials in the frame of the Li-Fe-P-O system and their high-throughput characterization. The samples will be investigated withrespect to the Li-distribution during (dis-)charging in different electrolytes using new modesof scanning electrochemical microscopy (SECM) in a glove box. Furthermore uniquecombined electro-chemical/mechanical experiments based on micromachined cantileverscoated with Li battery materials will be performed in a glove box in order to reveal stresseffects during Li (de-)intercalation. The project is expected to give a complete and for the firsttime spatially resolved picture of the complex mechanisms of Li transport and phasetransitions in nano-grained battery materials. From the theoretical and combinatorialinvestigations a route to improved materials will be pinpointed.