Dealloying Under Conditions of Significant Solid-State Mass Transport

技术摘要：本研究项目研究了合金系统中的脱合金动力学和形态演变，其中晶格和晶界扩散的固态传质过程在环境温度下很重要。在这项工作中的主要控制参数将是合金成分，晶粒尺寸的多晶主机，颗粒主机和温度的颗粒尺寸。待改变的电化学参数包括在固定电压（计时电流法）和固定电流（计时电位法）条件下的溶解。这将允许单独确定形态对所施加的电化学电势和去合金化速率的依赖性。为了研究这些问题的实验和计算相结合的方法。所研究的合金系统是Li-Sn、Li-Pb和Li-Cd。这些主体金属和类似的金属目前被认为是未来锂离子电池中的阳极储层，并且已经被选择用于研究，因为它们分别代表了主体晶体结构的变化，四方晶系、面心立方和六方密堆积，并且具有丰富的历史，具有丰富的热力学和动力学数据。电化学方法用于生产合金，测量脱合金速率和确定相关的固态质量传输速率。使用聚焦离子束加工和扫描电子显微镜检查脱合金形态。动力学蒙特卡罗模拟被用来模拟形态演变的电化学电位和dealloying rate.NON-TECHNICAL摘要：本研究探讨形态演变的低熔点锂合金dealloying过程中的功能。目前正在考虑将这种合金用于先进的锂离子电池，其中脱合金过程对应于这些电池系统放电期间发生的脱合金过程。这项研究可能产生的结果将对储能研究产生重大影响，特别是未来电池新材料的开发。当这个国家考虑其能源选择时，它将需要在电化学和材料科学方面具有综合专业知识的人来解决当前和未来的能源技术。该计划的研究范围将为本科生和研究生提供在综合材料电化学实验室环境中进行基础培训的机会。在教育和培训领域，PI将开发一门新的本科课程“电化学能量储存和生产的材料科学”，该课程与所有材料一起可供同事通过全球网络使用。

TECHNICAL SUMMARY:This research program examines the kinetics of dealloying and morphology evolution in alloy systems for which the solid-state mass transport processes of lattice and grain-boundary diffusion are significant at ambient temperature. The major control parameters in the work will be the alloy composition, grain size of the polycrystalline hosts, particle size in the particulate hosts and temperature. The electrochemical parameters to be varied include dissolution under conditions of fixed voltage (chronoamperometry) and fixed current (chronopotentiometry). This will allow for the separate determination of the dependence of morphology on the applied electrochemical potential and dealloying rate. In order to examine these issues a combined experimental and computational approach is used. The alloy systems under study are Li-Sn, Li-Pb and Li-Cd. These host metals and similar ones are currently being considered as anode reservoirs in future lithium-ion batteries and have been chosen for study since they represent variations in the host crystal structures, tetragonal, face-centered cubic and hexagonal close-packed, respectively, and have a rich history with abundant thermodynamic and kinetic data available. Electrochemical methods are used to produce the alloys, measure dealloying rates and determine associated solid-state mass transport rates. Dealloying morphologies are examined using focused ion-beam machining and scanning electron microscopy. Kinetic Monte Carlo simulations are used to model morphology evolution in dealloying as a function of the electrochemical potential and dealloying rate.NON-TECHNICAL SUMMARY:This research examines morphology evolution during dealloying of low melting point lithium alloys. Such alloys are currently being considered for use in advanced lithium-ion batteries in which the dealloying process corresponds to that occurring during discharge of these battery systems. The findings likely to emerge from this research will significantly impact research in energy storage and particularly the development of new materials for future batteries. As this country considers its energy options, it will need people with combined expertise in electrochemistry and materials science to address current and future energy technologies. The scope of research in this program will afford undergraduate and graduate students the opportunity for fundamental training in an integrated materials electrochemistry laboratory environment. More generally in the area of education and training, the PI will be developing a new undergraduate course in the "materials science of electrochemical energy storage and production," and the course together with all materials will be available for colleagues to use via the worldwide web.