EAGER: Mesoscopic modeling of complex chemical-physical processes at interfaces

在许多工程系统中，部件界面处发生的物理和化学反应对系统的性能至关重要，例如电池中的电化学反应、喷油器、泵和血管中的空化反应或化学反应器中的反应。在界面水平上理解物理现象和相之间的相互作用对于设计更高效的系统和新技术至关重要，例如高能量密度电池和药物输送方法。通过计算方法，我们可以可视化界面的物理性质，使其能够很好地研究界面过程，并隔离关键现象，以更好地理解系统内的化学-物理驱动力。此外，建模可以补充实验工作，以阐明许多复杂工程系统核心的基本化学-物理过程。例如，在电池电极中，最佳性能需要平衡可用于反应的表面积，可用于传输活性物质的孔隙空间，以及用于电荷传输的固体电极的连通性。忽略任何这些关键现象都会降低电池性能。本研究的重点是开发解决高能量密度锂电池空气电极界面化学物理过程所需的计算方法。该项目的重点是明确解决锂空气电池中空气电极复杂多孔几何结构中的界面和周围区域的模型。在这个项目中，中尺度模型的开发将侧重于使用光滑粒子流体动力学（一种基于拉格朗日粒子的建模方法）对锂金属电池的空气电极进行建模。空气电极是一种多孔的碳基材料，空气、电解质和电极的界面区域是电化学反应的场所。在放电过程中，Li+离子穿过电解液到达空气电极，在那里它们与氧气发生反应。在非质子电解质设计中，电化学反应产生不溶性过氧化锂（Li2O2）。Li2O2的积累使阴极表面钝化，并可能导致孔隙堵塞。这限制了电池在多次充放电循环中的容量，因为Li2O2的不完全溶解会降低容量。介尺度模型将专注于模拟电极的介尺度行为，以解决界面化学物理过程，如物质和电荷到反应位点的传输以及产生Li2O2的电化学反应。该模型将通过明确解析界面来研究中尺度物理，并将研究电极微观结构、电解质和反应位点浓度和位置之间的相互作用如何影响电极性能。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。

In many engineering systems, the physics and chemistry occurring at interfaces in a component are critical to the system’s performance, such as the electrochemical reactions in batteries, cavitation in fuel injectors, pumps and blood vessels, or reactions in chemical reactors. Understanding the physical phenomena and interactions between phases at the interfacial level is critical to designing more efficient systems and new technologies, such as high energy density batteries and drug delivery methods. With computational methods, we can visualize the physical nature of interfaces, making it well positioned to study interfacial processes and to isolate critical phenomena to better understand the chemical-physical driving forces within a system. Additionally, modeling can complement experimental work on elucidating the fundamental chemical-physical processes at the core of many complex engineering systems. For instance, in battery electrodes, optimal performance requires balancing the surface area available for reactions, the pore space available for transport of reactive species, and the connectivity of the solid electrode for charge transport. Neglecting any of these critical phenomena reduces battery performance. This study focuses on developing the computational methods needed to resolve chemical-physical processes at interfaces in the air electrode of high energy density lithium batteries. The project focuses on models that explicitly resolve the interfaces and surrounding regions within the complex porous geometry of the air electrode in a lithium-air battery. In this project, meso-scale model development will focus on modeling the air electrode of a lithium metal battery using smoothed particle hydrodynamics, a Lagrangian particle-based modeling method. The air electrode is a porous carbon-based material and the interfacial region where the air, electrolyte and electrode meet, is the site of the electrochemical reactions. During discharge, Li+ ions travel through the electrolyte to the air electrode where they react with oxygen. In an aprotic electrolyte design, the electrochemical reactions result in non-soluble lithium peroxide (Li2O2). The buildup of Li2O2 passivates the surface of the cathode and can lead to clogging of the pores. This limits the capacity of the battery over multiple charge/discharge cycles as the incomplete dissolution of Li2O2 decreases the capacity. The meso-scale model will focus on modeling the meso-scale behavior of the electrode to resolve the interfacial chemical-physical processes such as transport of species and charge to the reaction sites and the electrochemical reactions that produce Li2O2. The model will be used to investigate the meso-scale physics by explicitly resolving the interface and will study how the interplay between the electrode microstructure, electrolyte and reaction site concentration and locations affect electrode performance.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.