Effect of hydrodynamic interactions on electrochemical performance of flowable electrodes

一种被称为“可流动电极”的新型电极已被用于一些新兴的能源和环境相关技术，如用于存储电能的电化学流动电容器和用于处理微咸水的电容去离子。在可流动电极的工作过程中，一种由高度多孔的小碳珠和水电解质混合而成的浆液流入电化学电池，并被外加电压充电。离子通过碳珠的孔隙被吸附到碳珠的内表面以储存电荷。由于多孔碳珠相对于其质量具有巨大的内表面积，它们可以在很短的时间内储存或释放大量的离子和电子。与传统的可充电电池相比，这一过程允许更快速的充放电。流动电容器有可能实现比锂离子电池快100倍的充电速度和1000倍的寿命。此外，流架构使其可扩展到电网储能。实现这些电位需要详细了解浆液的详细配置如何影响电导率和充电。浆料内的电网络由间歇性接触的碳颗粒组成，导致电通路迅速中断和改造。因此，整个浆液在导电性和充电特性方面表现出独特的行为，这是可流动电极性能的关键。该项目将研究碳颗粒水平上的水动力相互作用如何影响可流动电极的关键性能。研究结果将有助于提高流动电极的效率，为能源和水资源的可持续发展做出贡献。该项目的跨学科性质为从高中到研究生阶段的学生提供了丰富的参与研究的机会。该项目结合实验和计算方法，探索直径为1至10微米的活性炭颗粒的流体动力学相互作用，以及可流动电极的电化学过程。新型微流体装置将被构建来直接观察颗粒相互作用，同时测量浆料的电学或电化学特性。介电流变装置将用于测量宏观层面的性质。计算工作将采用一种新的数值模型来模拟粒子的微流体动力学、粒子网络的拓扑变化电路及其耦合。实验数据将为计算模型提供关键参数，如粒子网络的电阻和电容。该计算模型将提取剪切速率和颗粒浓度对颗粒簇特征的影响，包括簇大小、长度和方向，以及它们对可流动电极的各向异性电导率和瞬态充电行为的影响。这些研究将为提高可流动电极在能源和环境技术中的性能提供知识。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。

A new type of electrode called a "flowable electrode" has been used in several emerging energy- and environment-related technologies, such as the electrochemical flow capacitor for storing electrical energy and capacitive deionization for treating brackish water. During the operation of a flowable electrode, a slurry of small, highly porous carbon beads mixed with an aqueous electrolyte flows into an electrochemical cell and is charged with an applied voltage. Ions are adsorbed to the interior surface of the carbon beads through their pores to store electrical charge. Because the porous carbon beads have enormous interior surface area relative to their mass, they can store or release a tremendous amount of ions and electrons in a very short time. This process allows more rapid charging and discharging compared with conventional rechargeable batteries. The flow capacitor has the potential to achieve 100 times faster charging and 1000 times longer lifetime than Li-ion batteries. Furthermore, the flow architecture makes it scalable for grid energy storage. Achieving these potentials requires detailed knowledge about how the detailed configuration of the slurry affects electrical conductivity and charging. The electrical network within the slurry consists of carbon particles in intermittent contact causing electrical pathways to be rapidly disrupted and reformed. Thus, the entire slurry displays unique behavior in electrical conductivity and charging characteristics, which are key to the performance of the flowable electrode. This project will investigate how hydrodynamic interactions at the carbon particle level affects the critical properties of flowable electrodes. The results will help improve efficiency of flow electrodes, which will contribute to sustainable developments in energy and water resources. The interdisciplinary nature of the project provides rich opportunities for students from high-school to graduate levels to participate in the research.This project combines experimental and computational approaches to explore the hydrodynamic interactions of activated carbon particles with diameters from 1 to 10 micrometers, and the electrochemical processes of flowable electrodes. Novel microfluidic devices will be constructed to directly observe particle interactions and, simultaneously, to measure the electrical or electrochemical properties of the slurry. Dielectric-rheo setups will be used to measure properties at the macroscopic level. The computational efforts will employ a new numerical model to simulate the micro-hydrodynamics of the particles, the topology-varying electrical circuit of the particle network, and their coupling. The experimental data will provide critical parameters such as the electrical resistance and capacitance of the particle network to the computational model. The computational model will extract effects of shear rate and particle concentration on the particle cluster characteristics, including cluster sizes, lengths, and orientations, and their effects on the anisotropic conductivity and transient charging behavior of the flowable electrode. The studies will produce knowledge to improve the performance of flowable electrodes in energy and environment technologies.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.