CAREER: Identifying reaction mechanisms for the formation of stable interphases in lithium metal batteries

电化学能量存储装置对于将全球能源经济从用于运输和能源产生的化石燃料转变至关重要。与最先进的石墨和含硅阳极相比，金属锂阳极通过增加能量密度提供了降低成本和增加采用的途径，但围绕稳定循环和安全性的挑战仍然存在。这些挑战的根源在于电极和液体电解质之间的界面，其中由于电解质溶剂和盐分子的（电）化学分解而形成固体电解质中间相（SEI）。Li金属电极被设计为在远远超过有用电解质的热力学稳定性窗口的情况下操作，并且长期循环只能通过电极-电解质界面的动力学稳定来实现。该研究计划将确定在高库仑效率电解质中形成SEI的电解质反应机制，并使用这种基本理解来设计和评估新的无氟电解质。该研究计划将与教育和推广活动紧密结合，通过纵向指导关系解决STEM教育中代表性不足的问题。该项目将设计并实施一个可持续发展大使计划，该计划将是一个基于队列的计划，为西北大学本科生和芝加哥公立学校高中生提供一对一的指导。锂离子电池中锂金属电沉积的稳定性是当今储能研究中最大的突出挑战之一。这个CAREER项目的中心假设是，随着对SEI形成反应的基本理解的提高，可以精确地设计新的电解质，通过促进理想的SEI反应和抑制不理想的途径来实现可逆的Li金属循环。为了更好地理解SEI形成反应，本项目将重点关注以下目标：1）确定自由基无机和有机电解质分解产物的结构和作用，2）原位监测SEI生长和老化，3）研究无氟电解质中的反应机制，旨在促进理想的SEI形成反应。 该研究将使用精心设计的非原位电子顺磁共振（EPR）实验和先进的原位表征工具，为电解质分解途径和提高锂金属循环效率的关键机制提供新的理解。在设计用于锂金属电池的无氟电解质材料时，我们可以采用更系统的方法，也可以证明对其他金属阳极电池化学成分（如钠、镁、钙和锌）有用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Electrochemical energy storage devices are critical for transitioning the global energy economy away from fossil fuels used in transportation and energy generation. Metallic lithium anodes offer an avenue to reduce cost and increase adoptions by increasing energy density compared to state-of-the-art graphite and silicon containing anodes, yet challenges around stable cycling and safety remain. The roots of these challenges lie at the interface between the electrode and the liquid electrolyte, where a solid electrolyte interphase (SEI) forms because of (electro)chemical breakdown of the electrolyte solvent and salt molecules. Li metal electrodes are designed to operate well beyond the thermodynamic stability windows of useful electrolytes and long-term cycling can only be enabled by kinetic stabilization of the electrode-electrolyte interface. This research program will identify the electrolyte reaction mechanisms that underpin SEI formation in high Coulombic efficiency electrolytes and use this fundamental understanding to design and evaluate new fluorine free electrolytes. This research program will be closely coupled with educational and outreach activities to address the issues of underrepresentation in STEM education through longitudinal mentoring relationships. This project will design and implement a Sustainability Ambassadors program which will be a cohort-based program for one-on-one mentoring with Northwestern University undergraduate students and Chicago Public School high school students.The stabilization of Li metal electrodeposition in lithium-ion batteries is one of the largest outstanding challenges in energy storage research today. The central hypothesis of this CAREER project is that with an improved fundamental understanding of SEI formation reactions, new electrolytes can be precisely engineered to enable reversible Li metal cycling by promoting desirable SEI reactions and suppressing undesirable pathways. To better understand SEI formation reactions, this project will focus on the following objectives: 1) identifying the structure and role of radical inorganic and organic electrolyte decomposition products, 2) in situ monitoring of SEI growth and aging, and 3) study of reaction mechanisms in fluorine-free electrolytes designed to promote desirable SEI forming reactions. The research will use carefully designed ex situ electron paramagnetic resonance (EPR) experiments and advanced in situ characterization tools will provide new understanding to the field regarding electrolyte decomposition pathways and key mechanisms that improve Li metal cycling efficiency. The insights developed here will allow for a more systematic approach to be taken when designing F-free electrolyte materials for Li metal batteries and may also prove useful for other metal anode battery chemistries such as sodium, magnesium, calcium, and zinc.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.