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

电化学储能装置对于使全球能源经济摆脱对运输和能源生产中使用的化石燃料的依赖至关重要。与最先进的石墨和硅阳极相比，金属锂阳极通过提高能量密度，为降低成本和增加采用率提供了一条途径，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，由于电解质溶剂和盐分子的（电）化学分解，形成了固体电解质界面（SEI）。锂金属电极被设计成可以在有用电解质的热力学稳定窗口之外运行，并且只有通过电极-电解质界面的动力学稳定才能实现长期循环。该研究项目将确定支撑高库仑效率电解质中SEI形成的电解质反应机制，并利用这一基本认识来设计和评估新的无氟电解质。该研究项目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项目，这将是一个基于群体的项目，为西北大学的本科生和芝加哥公立学校的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。CAREER项目的核心假设是，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锂金属循环。为了更好地了解SEI形成反应，该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，以及3)研究旨在促进理想SEI形成反应的无氟电解质中的反应机制。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，为提高锂金属循环效率的电解质分解途径和关键机制提供新的认识。在这里开发的见解将允许在设计锂金属电池的无f电解质材料时采用更系统的方法，并且也可能证明对其他金属阳极电池化学物质如钠，镁，钙和锌有用。该奖项反映了美国国家科学基金会的法定使命，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.