Hybrid all-Fe redox flow batteries: Coupling theory and experiment

为了将更多波动较大的可再生能源应用到我们的电网中，需要可靠的电能储存装置。为了使这一能源转换过程也可持续，重要的是使用依赖于地球上丰富的无毒材料的能源储存装置。铁(Fe)满足这些标准，可用于全铁氧化还原液流电池(IRFB)，从而为锂离子电池和钒氧化还原液流电池提供了一种有前途的可持续替代方案。然而，要实现这项技术，需要克服长度范围内的许多关键挑战。在纳米尺度上，需要智能接口设计来抑制寄生析氢反应。在微观尺度上，多孔的3D结构电极必须便于在孔内进行可逆镀铁和剥离。在宏观层面上，适当的再平衡系统必须处理氢气的释放，同时需要仔细选择操作条件，以减少由于不希望看到的镀铁/剥铁造成的产能损失。不幸的是，这些障碍不能相互独立地加以解决，而必须同时加以考虑。该项目的目标是通过使用跨尺度的联合理论和实验方法，建立对IRFB的全面的机械理解。只有多尺度地将实验和理论结合起来，才有可能对这个复杂的系统进行评估、理解和合理的改进。在理论方面，我们将把连续介质模型和分子模型结合起来。从分子尺度的电镀和剥离过程到系统尺度的操作条件的长度尺度，我们将通过应用和改进多尺度建模技术来涵盖相关过程。在实验方面，我们将通过在平面模型表面引入缺陷位来修改表面性质，将所获得的知识整合到三维多孔电极样品中，并在系统层面上测试其在实际操作条件下的性能。理论和实验将通过建立参数化和验证循环来结合，以得出接口、电极和系统设计的可靠和简明的建议。

Reliable electrical energy storage devices are required in order to implement more of the highly fluctuating renewable energy sources into our electrical supply grid. To make this energy transition process also sustainable, it is important to use energy storage devices that rely on earth-abundant and non-toxic materials. Iron (Fe) fulfils these criteria and can be used in all-Fe redox flow batteries (IRFB), thereby providing a promising sustainable alternative to lithium-ion batteries and vanadium redox flow batteries. However, many critical challenges across length scales need to be overcome to enable this technology. At the nanoscale, smart interface designs are needed to inhibit the parasitic hydrogen evolution reaction. At the microscale, porous 3D-structured electrodes must facilitate reversible Fe plating and stripping inside the pores. At the macroscale, suitable rebalancing systems must handle hydrogen evolution, while carefully chosen operating conditions are required to mitigate capacity loss due to undesired plating/stripping of Fe. Unfortunately, those obstacles cannot be tackled independent of each other, but must be considered simultaneously. The goal of this project is to establish a comprehensive mechanistic understanding of the IRFB by using a joint theoretical and experimental approach across scales. Only by coupling experiment and theory in a multiscale approach, it will be possible to assess, understand, and rationally improve this complex system. From the theoretical side we will combine continuum and molecular models. With length scales from plating and stripping processes on the molecular scale up to operating conditions at system scale, we will cover the relevant processes by applying and advancing multiscale modelling techniques. On the experimental side we will modify surface properties by introducing defect sites into planar model surfaces, integrate the knowledge gained into 3D porous electrode samples, and test their properties under realistic operating conditions on the system level. Theory and experiment will be coupled by establishing parameterization and validation cycles to arrive at reliable and concise recommendations for interface, electrode and system design.