EAGER: Investigation of Lithium-Air Battery Cathode Reaction Mechanisms through SERS-Active Electrode

朱-1505943该项目旨在开发用于电动汽车的锂空气电池，作为化石燃料汽车的替代品。为了与商用内燃机竞争，蓄电系统必须在能量密度、功率密度和可逆性方面得到显著提高。锂-空气电池具有显著提高能量密度的潜力，但它们仍然不成熟，存在许多问题，包括它们的阴极反应迟缓和不可逆转。由于锂-空气电池的正极反应机理尚不清楚，因此很难设计出循环性能更好的电极和电解液。本研究的主要目的是合成一种双连续的锂空气电池表面增强拉曼光谱(SERS)活性电极，并用拉曼光谱研究其充放电机理。这是一笔急切的赠款，以证明制造工艺的可行性。智力优势：该项目旨在制造SERS活性电极，以研究在阴极上形成的产品。制备组织良好的双连续3D多孔电极的基本原理是同时提供较大的有效表面积和改善电解液和氧气的扩散。锂-空气电池正极反应复杂，对局部电化学环境敏感。研究电池电极反应的机理对获得充放电过程中电极的化学信息具有重要意义。在这项工作中，PI计划使用聚合物模板来制造组织良好的双连续电极，该电极由原始的化学气相沉积的石墨烯制成。双连续电极可以提高锂-空气电池的动力学性能，减少堵塞引起的降解。为了增强拉曼信号，双连续电极将通过吸附均匀和规则组装的金纳米颗粒来修饰。修饰电极可允许通过表面增强拉曼光谱检测沉积在电极上的痕量中间化合物。PI建议使用具有稳定溶剂(二甲氧基乙烷、二甲基亚砜和四(乙烯)乙二醇二甲醚等)的修饰电极。制造锂空气电池。一套表征工具(包括拉曼光谱、傅里叶变换红外光谱、透射电子显微镜、X射线光电子能谱和X射线衍射仪)应该能够对空气阴极上的材料进行研究。特别令人感兴趣的是在充电和放电过程中沉积在阴极上的中间化合物，这将通过SERS拉曼光谱来阐明，以解决与电解液/电极稳定性相关的基本材料挑战。这项研究将为今后设计原位SERS拉曼表征技术提供依据，通过对电极上化学信息的持续研究来阐明阴极反应机理。最终，这可能为高性能、可逆锂空气电池提供新的工程解决方案。广泛的影响：需要了解电极反应机理，以提高电化学储能系统的容量和可循环性。这对于材料和工艺设计也是至关重要的。由于锂空气电池的理论容量很高，而且在消费和工业应用中对这些电池的需求可能很高，因此即使在可循环性或效率方面略有提高，潜在的影响也是相当大的。既要考虑经济效益，又要考虑环境效益，因为增加电池容量将降低替代率，并可能允许用新技术取代旧技术。这可能包括用电动马达取代内燃机，用于运输系统。与这项研究相关的概念将通过各种外展计划向更广泛的公众受众传播。当地的外展活动将包括面向4-6年级学生的科学奥林匹克周末，面向高中生与聚合物科学和聚合物工程研究所教授合作的UA-Harker计划。此外，国际学生联合会积极参与美国学生协会的SEED计划，以促进当地经济困难的高中生的研究活动。这些外展活动的目的是(1)展示实践纳米技术，(2)激发学生对科学和技术的兴趣，从而鼓励他们考虑在STEM领域就业，以及(3)教授与化学过程工程相关的挑战和机会。

Zhu - 1505943This project is aimed at developing lithium-air batteries for use in electrically powered vehicles as alternatives to vehicles that run on fossil fuels. To compete with commercial internal combustion engines, electricity storage systems have to be significantly improved in energy density, power density and reversibility. Lithium-air batteries have the potential to significantly enhance the energy density but they are still immature and suffer from many issues, including the fact that they have sluggish and irreversible cathode reactions. Because the cathode reaction mechanism of the lithium-air battery is unclear, it is very difficult to design electrodes and electrolytes that cycle better. The primary objective in this research is to synthesize a bicontinuous, SERS (surface-enhanced Raman spectroscopy)-active electrode for lithium-air batteries and study the mechanism of charging/discharging processes by Raman spectroscopy. This is an EAGER grant to demonstrate the feasibility of the fabrication process.Intellectual Merit: This project seeks to fabricate the SERS-active electrodes to study the products formed on the cathode. The rationale for fabricating well organized bi-continuous 3D porous electrodes is to provide, simultaneously, a large effective surface area and an improvement in the electrolyte and oxygen diffusion. Lithium-air battery cathode reactions are complicated and sensitive to the local electrochemical environment. It is important to study the mechanisms of the battery electrode reactions to gain chemical information about the electrode throughout the charging/discharging process. In this work, the PI plans to use polymer templates to fabricate well-organized bicontinuous electrodes made of pristine chemical vapor deposited graphene. The bi-continuous electrodes can enhance the lithium-air battery kinetic performance and reduce the clog induced degradationTo enhance the Raman signals, the bi-continuous electrodes will be modified by the adsorption of uniform and regularly assembled gold nanoparticles. The modified electrodes may allow the detection, by surface-enhanced Raman spectroscopy, of trace intermediate compounds deposited on the electrodes. The PI proposes to use the modified electrode with stable solvents (Dimethoxyethane, Dimethyl sulfoxide and Tetra(ethylene) glycol dimethyl ether etc.) to fabricate lithium-air battery. A suite of characterization tools (including Raman, FTIR, TEM, XPS, and XRD) should enable the investigation of the materials on the air-cathode. Of particular interest are intermediate compounds deposited on the cathode during the charging and discharging processes that will be elucidated by SERS Raman spectroscopy to address fundamental material challenges associated with electrolyte/electrode stability. This research will provide the bases to design in-situ SERS Raman characterization techniques in the future, which may elucidate the cathode reaction mechanisms through the continuous investigation of the chemical information on the electrodes. Ultimately this may point to new engineering solutions for high performance, reversible lithium-air batteries.Broader Impacts: Understanding the electrode reaction mechanism is needed to improve capacity and cyclability of electrochemical energy storage system. This is also pivotal for material and process design. Due to the high theoretical capacitance of lithium-air battery and the possible high demand for these batteries in consumer and industrial applications, the potential impact from even a modest advance in cyclability or efficiency is quite large. There are both economic and environmental benefits to consider because increased battery capacity will decrease the replacement rate and may allow for the substitution of new technology for old. This could include the replacement of the internal combustion engine with electrical motors for uses in transportation systems. Dissemination of concepts associated with this research will be to a broader, public audience through various outreach programs. Local outreach efforts will include Science Olympiad weekend for students in grades 4-6, the UA-Harker program for high-school students working with professors in the institute of polymer science and polymer engineering. Additionally, the PI's group is active in ACS SEED program to promote the research activities of economically disadvantaged local high school students. The goal of these outreach activities are to (1) illustrate hands-on nanotechnology, (2) excite students about science and technology so that they may be encouraged to consider careers in STEM fields, and (3) teach about challenges and opportunities associated with the engineering of chemical processes.