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资源产生的电力，或通过可再生资源充电为零排放电动汽车提供动力，帮助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，这两个指标决定了电池可以储存多少能量，以及需要多长时间才能完全充电。显著提高容量的一种方法是用包括硅(Si)、锗(Ge)和锡(Sn)元素的合金型阳极材料取代传统的石墨阳极。然而，这些合金材料在充电后会膨胀，从而促进机械故障。该项目将通过将元素硒(Se)添加到由微米级颗粒制成的合金型阳极来解决这一问题。由此得到的Se掺杂微粒可能能够减少阳极的膨胀。先进的成像和计算研究将对这些过程有一个基本的科学理解，长期目标是开发商业上负担得起的高性能负极材料，用于更好的电池。这项研究将是印第安纳大学、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的结果。此外，与该项目相关的教育活动将在这三个机构之间进行协调，包括将研究整合到本科和研究生课程讲座中，本科生和K-12教师参与研究，并通过开发与能源相关的简短动画视频向大学预科学生推广。研究的总体目标是发展对锂离子电池合金型阳极锂化和脱锂过程中掺硒Ge和Sn微粒子的电化学、物相和形态动力学的基本了解。该研究计划有两个目标。第一个目标是研究Se掺杂材料在锂化和脱锂过程中的动力学，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，将确定含Se非活性相的组成，并确定其离子电导率。此外，还将研究活性/非活性混合相对Ge和Sn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模拟，建立锂离子电池性能与Se-Ge和Se-Sn微结构变化之间的关系。建立了一个综合了电化学反应、组分扩散、界面效应以及大弹塑性变形过程的相场模型，以模拟Ge-Se或SnSe颗粒在锂化和脱锂过程中相、形貌和应力的同时演化。由于未来的高容量电极材料可能会有较大的体积变化，因此研究结果可能会使这些新的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.