Fundamental Understanding of SEI Effects on Li Dendrite Formation and Growth

锂离子电池是为当今的电动和混合动力汽车提供动力的最先进的选择。电动汽车的能量密度和功率能力是有限的，需要新的化学物质来提高电动汽车的性能。用金属锂取代商品化锂离子电池中的石墨电极，有望显著提高电池的能量密度。然而，由于锂金属在充放电循环中沉积不均匀，在电池中使用金属锂电极的研究努力失败了。该项目将利用几种最先进的计算机模拟工具和实时显微镜技术来研究各种电池电解液中的金属锂沉积。特别是，该项目将解决电解液与金属锂反应的副产物如何影响锂树枝晶的生长和形态。这些细丝在电池中的形成会使电池短路，从而导致故障。该项目的研究成果将为开发高能量密度金属锂电池铺平道路。这一项目将为伊利诺伊大学芝加哥分校(UIC)提供几个将研究与本科生和研究生教育以及外联活动相结合的场所。研究生和本科生将接触到几种先进的显微镜工具和计算机模拟包，这将提供一套独特的研究体验。计划开展外展活动，向高中生和本科生传播这项研究的结果，并激励他们学习与电化学储能技术有关的知识。在UIC-机械和工业工程系开放日和UIC暑期青年方案期间，将为STEM中的当地高中女生和代表性不足的学生开展外联活动。锂金属电极有可能使轻质和高能量密度的电池用于交通运输和推进应用。实现这一目标的一个主要障碍仍然是以纤维或树枝状形态出现的锂金属的不均匀沉积。这些锂树枝会刺穿电池的电解液和隔膜，最终导致电气短路，有可能引发火灾。人们对Li枝晶生长的预防机制进行了大量的研究，但由于对枝晶的形成和生长缺乏基本的了解，这方面的进展有限。Li枝晶是如何在固体电解质界面(SEI)的影响下形成、长大和分裂的，这些基本问题仍然没有答案。PIS将采用多尺度和多物理的方法，使用先进的实验和理论方法，如原位透射电子显微镜(TEM)、手术中光学显微镜、电化学阻抗谱(EIS)、密度泛函理论(DFT)计算和相场建模(PFM)来研究SEI影响下Li树枝晶的生长。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Lithium ion batteries are the state-of-the-art choice for powering today's electric and hybrid electric vehicles. The energy density and power capability are limited; new chemistries are needed to increase the performance of the electric vehicle. Replacing the graphite electrodes in the commercialized lithium-ion batteries with lithium metal is expected to boost the energy density of batteries significantly. However, research efforts to use lithium metal electrodes in batteries have failed due to non-uniform deposition of lithium metal during charge and discharge cycles. This project will utilize several state-of-the art computer simulation tools and real-time microscopy techniques to investigate the lithium metal deposition in various battery electrolytes. In particular, the project will address how the by-products of electrolyte reactions with lithium metal affect the growth and morphology of lithium dendrites. The formation of these filaments in the battery shorts the battery causing failure. The results of this project will pave the road for developing high energy density lithium metal batteries. Several venues for integrating research with undergraduate and graduate education and outreach activities at University of Illinois at Chicago (UIC) will occur as a result of this project. Graduate and undergraduate students will be exposed to several advanced microscopy tools and computer simulation packages that will provide a unique set of research experience. Outreach activities are planned to disseminate the results of this study to high school and undergraduate students and motivate them to pursue studies related to electrochemical energy storage technologies. Outreach activities for local high school female and underrepresented students in STEM during the UIC-Mechanical and Industrial Engineering Department Open House and UIC Summer Youth Program will be conducted. Lithium-metal electrodes have the potential to enable lightweight and high energy density batteries for transportation propulsion applications. A major obstacle to achieve this goal remains on the non-uniform deposition of lithium metals that appear in the form of fibrous or dendritic morphology. These lithium dendrites can poke through the electrolyte and separator of batteries and eventually result in electrical short circuit potentially causing fire. Significant research has been conducted to develop prevention mechanisms of Li dendrite growth; however, the progress has been limited due to the lack of fundamental understanding on the formation and growth of the dendrites. The fundamental questions such as how Li dendrites are formed, grown and split under the influence of the solid electrolyte interface (SEI) remain unanswered. The PIs will employ a multi-scale and multi-physics approach using advance experimental and theoretical methods such as in-situ transmission electron microscopy (TEM), in-operando optical microscopy, electrochemical impedance spectroscopy (EIS), density functional theory (DFT) calculations, and phase-field modeling (PFM) to study the growth of Li dendrites under the SEI influence.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.