Collaborative Research: Dynamics of chalcogenide-doped high capacity lithium-ion battery anode materials during cycling using in situ imaging

可充电锂离子电池通过存储风能和太阳能等间歇性可再生能源产生的电力，或为使用可再生能源充电的零排放电动汽车提供动力，有助于实现可持续能源系统。锂离子电池的两个关键性能指标是容量和充电率，它们决定了电池可以储存多少能量以及完全充电需要多长时间。一种显著提高容量的方法是用合金型阳极材料取代传统的石墨阳极，这种材料包括硅（Si）、锗（Ge）和锡（Sn）等元素。然而，这些合金材料在充注后会膨胀，从而导致机械故障。该项目将通过将元素硒（Se）添加到由微米大小的颗粒制成的合金型阳极中来解决这个问题。所得到的掺硒微粒可以减少阳极的膨胀。先进的成像和计算研究将获得对这些过程的基本科学理解，长期目标是为更好的电池开发商业上负担得起的高性能阳极材料。这项研究将由印第安纳大学、密西西比州立大学和德克萨斯大学奥斯汀分校三所大学的研究人员共同努力。此外，与此项目相关的教育活动将在这三个机构之间进行协调，包括将研究纳入本科和研究生课程的讲座，让本科生和K-12教师参与研究，并通过制作与能源有关的短片动画向大学预科学生推广。该研究的总体目标是在锂离子电池合金型阳极的锂化和去锂化反应过程中，对掺杂硒的Ge和Sn微粒的电化学、材料相和形态动力学有一个基本的了解。研究计划有两个目标。第一个目标是研究硒掺杂材料在锂化和去锂化过程中的动力学，重点是通过原位x射线粉末衍射（XRD）、透射电子显微镜（TEM）和透射x射线显微镜（TXM）原位测量相和形貌的变化。同时，含硒非活性相的组成将被确定，其离子电导率将被确定。此外，还将研究活性/非活性混合相对锗基和锡基电极循环性能的影响。第二个目标是通过上述实验和理论建模，建立锂离子电池电池性能与Se-Ge和Se-Sn电极微观结构变化之间的相关性。将建立一个相场模型，该模型集成了电化学反应、物质扩散、界面效应以及大弹塑性变形过程，以模拟Ge-Se或Sn-Se颗粒在锂化和去锂化过程中相、形态和应力的同步演化。由于未来的高容量电极材料可能会有很大的体积变化，因此研究结果可能会使这些新电池系统的开发成为可能。

Rechargeable lithium ion batteries help to enable sustainable energy systems by storing electricity generated by intermittent renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. The two key performance measures of lithium ion batteries are capacity and recharge rate, which determine how much energy a battery can store and how long it takes to fully recharge. One approach to significantly improve capacity is to replace conventional graphite anodes with alloy-type anode materials that include the elements silicon (Si), germanium (Ge), and tin (Sn). However, these alloy materials swell up after charging, which promotes mechanical failure. This project will address this issue by adding the element selenium (Se) to alloy-type anodes made from micrometer sized particles. The resulting Se-doped microparticles may be able to reduce swelling of the anode. Advanced imaging and computational studies will gain a fundamental scientific understanding of these processes, with the long-term goal of developing commercially affordable, high-performance anode materials for better batteries. The research will be a collaborative effort between researchers at three universities - Indiana University, Mississippi State University, and the University of Texas at Austin. Furthermore, the educational activities associated with this project will be coordinated between these three institutions, and will include integration of the research into undergraduate and graduate course lectures, involvement of undergraduate students and K-12 teachers in research, and outreach to pre-college students through development of short, energy-related animated videos.The overall goal of the research is to develop a fundamental understanding of the electrochemical, material phase, and morphological dynamics of Se-doped Ge and Sn microparticles during lithiation and de-lithiation reactions with lithium ion battery alloy-type anodes. The research plan has two objectives. The first objective is to investigate the dynamics of Se-doped materials during lithiation and de-lithiation, focusing on in situ measurement of phase and morphology change via in situ X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and transmission X-ray microscopy (TXM). Concurrently, the composition of the Se-containing inactive phase will be identified and its ionic conductivity will be determined. Furthermore, the effect of the active/inactive mixed phases on cycling performance for both Ge- and Sn-based electrodes will be studied. The second objective is to develop correlations between lithium ion battery cell performance and changes in Se-Ge and Se-Sn electrode microstructure through the afore-mentioned experiments and theoretical modeling. A phase field model that integrates the processes of electrochemical reaction, species diffusion, interfacial effects, as well as large elastoplastic deformation will be developed to simulate the concurrent evolution of phases, morphologies and stress within a Ge-Se or Sn-Se particle during lithiation and de-lithiation. Since it is likely that future high-capacity electrode materials will have large volume changes, the outcomes from the research may enable development of these new battery systems.