UNS: Mechanistic Approach to Design Robust Composite Polymer Cathodes for Potassium-Air Batteries

PI：Vishnu-Baba SundaresanProposal编号：1512405充电电池通过存储风能和太阳能等可再生资源产生的电力，或通过使用可再生资源为零排放电动汽车充电，支持可持续能源系统的发展。然而，目前使用的锂离子电池的储能容量相对较低。金属-空气电池具有比锂离子电池高得多的储能能力，因为它们通过一种不同的过程存储电荷，这种过程利用空气中的氧气来帮助转移电子。但这一过程也会增加充电时间。在金属-空气电池中，钾-空气系统是速度最快的，但容易出现故障。这个项目的目标是对失效机理有一个基本的了解，然后利用这个了解来开发一种新的基于导电聚合物的阴极设计，提供更好的氧原子传输控制。这样，钾-空气电池系统就可以走向最终的商业应用。作为这项研究的一部分，研究生和本科生将获得进一步开发金属-空气电池系统的技能。首席调查人员还将组织关于储能材料和智能材料的工作坊，以在俄亥俄州大哥伦布市地区的初中生和高中生中推广STEM教育。金属-空气电池具有比同类金属离子电池更高的电化学储能能力。在金属-空气电池中，钾-空气系统使用氧和超氧化物之间的单电子氧化还原过程，以改善与其他金属-空气电池系统相关的低氧还原/放出速率。然而，钾空气电池的根本局限性是分子氧从正极到钾阳极的交叉，导致在负极表面形成超氧化物钾。这一过程会导致自放电，并降低可参与储能的金属的可用性。这项研究的目的是研究导电聚合物和碳载体材料形成复合阴极的可行性，以调节阴极中的氧还原反应，防止分子氧向阳极扩散。导电聚合物是一种功能梯度的纳米结构聚吡咯膜，具有优化的氧化还原位置密度，碳载体材料是还原的石墨烯氧化物。将使用电聚合过程来制造膜，从而使阴极的孔隙率在膜的厚度上逐渐减小。假设梯度多孔结构将阻止分子氧的渗透，从而提高钾-空气电池的性能寿命。拟议的研究计划将从机理上理解导电聚合物在复合阴极中的电荷存储，这是法拉第过程中机械应力、气体扩散和电化学还原反应的原因。作为该计划的一部分，将量化与导电聚合物中产生的体积应力有关的化学机械系数，以及它们在提高钾空气电池的能量密度和比功率方面的应用。该研究计划有四个具体的任务：1)电化学合成功能梯度的纳米结构聚吡咯膜；2)表征该膜作为钾-空气电化学电池的阴极；3)构建包含导电聚合物复合阴极的钾-空气电池；4)电池性能测试(容量、功率、循环)。研究成果将促进对金属-空气电池系统用导电聚合物中的能量存储和转换的更一般和更机械的理解，来自该研究的概念将被引入到能量存储材料课程中。

PI: Vishnu-Baba SundaresanProposal Number: 1512405Rechargeable batteries support the development of sustainable energy systems by storing electricity generated by renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. However, lithium ion batteries now in use have relatively low energy storage capacity. Metal-air batteries offer the potential for much higher energy storage capacity than lithium-ion batteries because they store electrical charge by a different process that uses oxygen in air to help transfer electrons. But this process can also increase charging times. Of the metal-air batteries, the potassium-air system is among the fastest, but is prone to failure. The goal of this project is develop a fundamental understanding of the mechanism of failure, and then use this understanding to develop a new cathode design based on conducting polymers that provides better control of oxygen atom transport. In this way, potassium-air battery systems can move forward towards eventual commercial application. As part of this research, graduate and undergraduate students will be given the skills to further develop metal-air battery systems. The principal investigators will also organize workshops on energy storage materials and smart materials to promote STEM education among middle and high school age students in greater Columbus, Ohio area. Metal-air batteries offer the potential for high electrochemical energy storage capacity that exceeds that of comparable metal ion batteries. Of the metal-air batteries, the potassium-air system uses a one-electron redox process between oxygen and superoxide to improve upon the low rates of oxygen reduction/evolution associated with other metal-air battery systems. However, the fundamental limitation of potassium-air batteries is the crossover of molecular oxygen from the cathode to potassium anode, leading to the formation of potassium superoxide on the anode surface. This process causes self-discharge and reduces the availability of metal that can participate in energy storage. The goal of the proposed research is to investigate the feasibility of a composite cathode formed from conducting polymers and carbon support materials to regulate the oxygen reduction reaction in the cathode and prevent the diffusion of molecular oxygen to the anode. The conducting polymer is a functionally graded, nanostructured polypyrrole membrane with an optimized density of redox sites, and the carbon support material is reduced graphene oxide. An electropolymerization process will be used to make the membrane so that the porosity of the cathode gradually decreases across the thickness of the membrane. It is hypothesized that the graded porous structure will block molecular oxygen crossover, thereby enhancing the performance lifetime of the potassium-air battery. The proposed research plan will develop a mechanistic understanding of charge storage of the conducting polymers within the composite cathode that accounts for mechanical stress, diffusion of gases, and electrochemical reduction reactions during faradaic processes. As part of this plan, the chemo-mechanical coefficients that relate volumetric stress generated in conducting polymers and well as their application for increasing the energy density and specific power of potassium-air batteries will be quantified. The research plan has four specific tasks: 1) electrochemical synthesis of the functionally graded, nanostructured polypyrrole membrane; 2) characterization of this membrane as the cathode for a potassium-air electrochemical cell; 3) construction of potassium-air battery containing the conducting polymer composite cathode, and 4) battery performance measurements (capacity, power, cycling). The research outcomes will advance a more generic and mechanistic understanding of energy storage and conversion in conducting polymers for metal-air battery systems, and concepts derived from the research will be introduced into an energy storage materials course.