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

电化学储能装置对于全球能源经济从用于交通运输和能源生产的化石燃料的转变至关重要。与最先进的石墨和含硅阳极相比，金属锂阳极提供了一条降低成本和增加采用率的途径，但围绕稳定循环和安全性的挑战依然存在。这些挑战的根源在于电极和液体电解液之间的界面，在那里由于电解液溶剂和盐分子的(电)化学击穿而形成固体电解质界面(SEI)。锂金属电极的设计远远超出了有用电解液的热力学稳定窗口，只有通过电极-电解液界面的动力学稳定才能实现长期循环。这项研究计划将确定支持高库仑效率电解液中SEI形成的电解液反应机理，并利用这一基本认识来设计和评估新的无氟电解液。这项研究计划将与教育和外展活动紧密结合，通过纵向指导关系解决STEM教育中代表性不足的问题。该项目将设计和实施可持续发展大使计划，这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能量存储研究中最大的突出挑战之一。这个职业项目的中心假设是，随着对SEI形成反应的基本了解的改善，可以精确地设计新的电解液，通过促进理想的SEI反应和抑制不希望的途径，实现可逆的锂金属循环。为了更好地了解SEI的形成反应，该项目将集中于以下目标：1)确定自由基无机和有机电解液分解产物的结构和作用，2)现场监测SEI的生长和老化，以及3)研究旨在促进理想的SEI形成反应的无氟电解液的反应机理。这项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，将为该领域提供关于电解液分解途径和提高锂金属循环效率的关键机理的新理解。这一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智力价值和更广泛的影响审查标准进行了评估，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.