Safe, High-Performance, Polymer Electrolyte for Lithium Batteries

[摘要]kofinas， PeterIntellectual Merit：锂离子电池广泛使用的关键障碍之一是其潜在的灾难性故障。当电池被热或电滥用时，它们的温度会升高，可燃液体电解质和带电电极之间的放热反应会导致电池燃烧，从而引起安全问题。虽然电极的改进最终将使未来的电池更节能，需要更少的活性材料，但安全性和形状仍然主要由电解质控制。通过将聚合物电解质与离子液体结合，得到的固体系统将具有所有所需的性能，并且具有足够的导电性，可以用作电池，这将是固有的安全，因为不再有易燃的液体成分。固体聚合物电解质的保形和安全特性也将使电池电量受益匪浅。本研究的目的是更好地了解具有增强性能的新型薄膜固体聚合物电解质的电化学性能和微观结构。实验旨在探索新的离子液体化学性质，同时充分表征聚合物IL共混物的电化学和微观结构，同时更好地了解固体电解质界面相（SEI）的性质。将追求下列目标：以前从未合成过的化学物质将由磺胺和四氢噻吩结构组成。利用核磁共振和质谱技术对其化学结构进行表征。固体电解质由聚氧乙烯（PEO）基均聚物和PEO嵌段共聚物与合成的ILs混合组成，并通过溶液铸造制备，并优化其高功率和能量输送。3. 优化后，将完成完整的电化学表征，以便更好地了解锂离子在体中和SEI中的运动。SEI将通过差示扫描量热法（DSC）和加速速率量热法（ARC）进行研究，以确定细胞内组成材料的反应速率和机制。交流阻抗实验将允许确定体积和界面电阻。过电压研究将决定这一间期的稳定性。扫描电镜成像和质谱将确定SEI和分解产物的程度。随着本研究提出的新型硫基离子液体化合物的发展，固体聚合物电解质的性能特性有望得到改善。这种符合形状的材料可以很容易地缠绕成线圈或加工成涂层或薄片，从而提供具有集成电子器件的大面积设备。有效地了解固体电解质体系电化学性能增强背后的机制将极大地有利于下一代电池的设计。更广泛的影响：这项研究的更广泛的影响是，它最终将有助于推动一种有吸引力的替代技术，以取代可燃和腐蚀性液体电解质。所提出的聚合物电解质系统在机械性能和产品设计上都具有灵活性。离子液体提供了一个有吸引力的选择，对基于硫的新结构的电化学理解将导致这些新化合物的进一步潜在用途。固体电解质间相（SEI）是电池中最重要但却最不为人所知的元素之一。对聚合物电解质SEI的进一步了解，将使设计定制界面成为可能，为下一代更安全、寿命更长的电池提供可能。这个项目连接了电化学、聚合物科学和化学工程的基本概念。除了对科学的影响外，建议计划亦会广泛影响工程教育，培养不同教育水平和不同背景的学生。这种培训将使他们在各行各业或学术界取得成功。这项工作的结果将发表在同行评议的期刊上，并在专业会议上发表。政府计划采取几项举措，包括协助本科生和研究生教育、研究生辅导和培训来自少数族裔富裕社区学校的高中生的具体项目。PI还计划指导马里兰大学（University of Maryland）一个多元化的大学生“宝石”（Gemstone）团队储能项目。Gemstone的学生是由同学、教师和工作人员组成的生活学习社区的成员，他们共同努力丰富本科体验。这个社区挑战并支持学生在研究、团队合作、沟通和领导技能方面的发展。被指导的学生团队将以论文的形式向该领域的领导者展示其储能项目，学生完成该项目并获得引用和切实的成就感。

Abstract1157590Kofinas, PeterIntellectual Merit:One of the key barriers to the widespread use of lithium-ion batteries is their potential for catastrophic failure. When cells are thermally or electrically abused, their temperature can rise and exothermic reactions between the combustible, liquid electrolyte and the charged electrodes can cause the battery to combust, giving rise to safety concerns. While improvements in the electrode would ultimately make the future battery more energy efficient, requiring less active material, safety and shape are still largely controlled by the electrolyte. By combining a polymer electrolyte with ionic liquids, the resultant solid system will possess all the desired properties and be conductive enough to be useful as a battery, which will be inherently safe because there is no longer a flammable liquid component. Battery power would also benefit greatly from the conformal and safe nature of solid polymer electrolytes. The goal of this research is to better understand the electrochemical properties and microstructure of novel thin film solid polymer electrolytes with enhanced performance. Experiments have been designed to explore new ionic liquid chemistries, and at the same time fully characterize the electrochemistry and microstructure of the polymer IL blend, while developing a better understanding the nature of the solid electrolyte interphase (SEI). The following objectives will be pursued:1. Never synthesized before IL chemistries will be developed consisting of sulfonium and tetrahyrdothiophenium architectures. The chemical structure of the novel ILs will be characterized using nuclear magnetic resonance and mass spectrometry.2. Solid electrolytes consisting of polyethylene oxide (PEO)-based homopolymers and block copolymers of PEO blended with the synthesized ILs will be prepared via solution casting, and optimized for high power and energy delivery. 3. Upon optimization, a full electrochemical characterization will be completed to allow better understanding of the movement of lithium ions in the bulk and at the SEI. The SEI will be investigated by differential scanning calorimetry (DSC) and accelerated rate calorimetry (ARC), to determine the reaction rates and mechanisms of the constituent materials within the cell. AC impedance experiments will allow the determination of the bulk and interfacial resistance. Overvoltage studies will determine the stability of this interphase. SEM imaging and mass spectroscopy will identify the extent of the SEI and breakdown products. With the development of novel sulfur based ionic liquid compounds proposed in this research, improved performance characteristics are expected of the solid polymer electrolyte. Such shape-conforming materials could be easily wound up into coils or processed as coatings or sheets, thus providing large area devices with integrated electronics. Effectively understanding the mechanism behind the enhanced electrochemical performance of the proposed solid electrolyte systems will greatly benefit the design of the next generation of batteries.Broader Impacts:The broader impact of this research is that it will ultimately help push forward an attractive alternative technology to combustible and corrosive liquid electrolytes. The proposed polymer electrolyte system offers flexibility in both mechanical properties and product design. Ionic liquids offer an attractive option and the electrochemical understanding of novel architectures based upon sulfur will lead to further potential uses for these novel compounds. The solid-electrolyte interphase (SEI) is among the most important yet least understood elements of a battery. Further insight into the polymer electrolyte SEI, would enable the design of tailored interfaces for a future generation of safer batteries with longer lifetimes.This project bridges fundamental concepts of electrochemistry, polymer science, and chemical engineering. In addition to the impacts on science, the proposed project will also broadly impact engineering education, training students of different educational levels and from diverse backgrounds. This training will poise them for successful careers in a wide range of industries or academia. Findings from this work will be published in peer-reviewed journals and presented at professional meetings. Several initiatives are planned including specific programs that assist in undergraduate and graduate education, graduate student mentoring, and training of high school students from schools in minority-rich communities. The PI also plans to mentor a diverse undergraduate "Gemstone" team project on energy storage at the University of Maryland. Gemstone students are members of a living-learning community comprised of fellow students, faculty and staff who work together to enrich the undergraduate experience. This community challenges and supports the students in the development of their research, teamwork, communication and leadership skills. The mentored team of students will presents its energy storage project in the form of a thesis to leaders in the field, and the students complete the program with a citation and a tangible sense of accomplishment.