Optimisation of flow of electrolytes through electrodes in organic aqueous redox flow batteries

该项目的主要目的是通过制造电极来优化电解液流动分配和氧化还原过程，从而提高有机水氧化还原液流电池(OARFBs)的性能。要通过新的制造工艺优化的主要性能指标是：-提高电极上电解液分布的均匀性。这提高了局部电流/电压分布的一致性，提高了电池性能的寿命，从而提高了OARFB成本。它还可能增加可用的反应地点的总数，因为电解液供应给以前未得到充分利用的地区。-减少电极上的压降。这减少了泵浦能量的损失。-改善电化学性能为实现这一目标，次要目标包括：-开发新的制造工艺，以形成碳毡和碳纸(目前最流行的电极材料)的图案，并在电极中引入流动通道，例如使用激光处理。-测试流通式OARFBs中的沟槽电极和非沟槽电极，以确定压降和电化学性能的任何差异。-模拟电解液通过槽道和非槽道电极的流量分布，以支持电池测试的结果。-使用核磁共振成像原位成像电极中的电解质流动。-综合从电池测试、建模和核磁共振测试中收集的信息，以更清楚地了解电解液在电极中的流动行为。作为这项工作的一部分，进一步探索的领域包括通过在碳毡或纸上添加纳米颗粒和碳纳米管来制造杂化电极，以及使用层次化结构作为电极设计的灵感。公正和文献：RFB的电化学性能与电极中电解液的分布密切相关。RFB由于电极压降而产生的泵浦损失也与流量分布有关。因此，优化通过电极的流量有可能使这两个性能指标都受益，从而降低氧化还原液流电池的成本，从而支持其部署，这是电网规模可再生能源存储所需的。对电极进行仔细的结构修饰，有可能改善电解液在电极中的流动分布。结构改造还避免了对潜在有毒、稀有或昂贵材料的需要，因此该项目最初的重点将是结构改造，而不是化学改造。虽然通过电极结构进行流量优化可以应用于许多电池化学，但本项目将重点关注有机水性RFB的流量优化。这是因为与市场上领先的全钒RFB(VRFBS)相比，它们的潜在成本更低，有机材料丰富，毒性更低。目前普遍缺乏对OARFB电极结构改性的研究。虽然已经有一些关于VRFB的结构修饰的研究，但这往往与添加特定于钒化学的催化剂有关，例如在碳纤维上生长的钛纳米线。向电极添加通道是电极修饰的相当简单的处理步骤。文献中有一项研究使用不同的设计来模拟电极中通道的电位效应，另一项研究以简单的形式将通道物理地添加到电极中。两者都表明这种方法很有前途，但缺乏对这种方法的广泛研究，也缺乏优化设计的开发。此外，尽管近年来已经探索了一些电极的原位流动成像方法(即热成像和荧光显微镜)，但没有一种方法能够实现理解碳毡中流动所需的3D成像。

The main aim of this project is to improve the performance of organic aqueous redox flow batteries (OARFBs) by manufacturing electrodes that optimise electrolyte flow distribution and redox processes. The main performance metrics to be optimised through new fabrication processes are: -Increased uniformity of electrolyte distribution across the electrode. This increases uniformity of local current/voltage distribution, increasing longevity of cell performance and hence OARFB cost. It may also increase the total number of reaction sites available, as the electrolyte is supplied to areas previously underutilized. -Reduction of pressure drop over electrodes. This reduces pumping energy losses. -Improvement of electrochemical performance To achieve this, secondary aims include: -The development of new manufacturing processes to pattern carbon felt and carbon paper (currently the most popular electrode materials) and introduce flow channels in the electrodes, for instance using laser processing. -To test channelled & non channelled electrodes in flow-through OARFBs, to determine any differences in pressure drop and electrochemical performance. -To model flow distribution of electrolyte through the channelled & non channelled electrodes, to support the results of the cell tests. -To use an MRI to image electrolyte flow in the electrode in situ. -To synthesize information gathered from cell testing, modelling and MRI testing, to provide increased clarity on the flow behaviour of the electrolyte in the electrode. Further areas to explore as part of this work includes the fabrication of hybrid electrodes by addition of nanoparticles and carbon nanotubes to carbon felt or paper, and the use of hierarchal structure as inspiration for electrode design.Justification & literature: The electrochemical performance of RFBs is strongly related to the distribution of the electrolyte in the electrode. The pumping losses incurred by an RFB due to pressure drop across the electrode are also dependent on the flow distribution. Therefore, optimization of flow through the electrode has the potential to benefit both these performance metrics, lowering the cost of redox flow batteries and hence supporting their deployment, which is required for the storage of grid scale renewable energy. Careful structural modification of the electrode has the potential to improve the flow distribution of the electrolyte in the electrode. Structural modification also avoids the need for potentially toxic, rare or expensive materials, and therefore the initial focus of this project will be on structural rather than chemical modification. Although flow optimization via electrode structuring could be applied to many cell chemistries, this project will focus on optimising flow for organic aqueous RFBs. This is due to their potential lower cost compared to the market leading all vanadium RFB (VRFBS), abundance of organic material and lower toxicity. There is a general lack of research into structural modification of electrodes for OARFB. Although there has been some investigation into structural modification for VRFBs, it is often related to addition of catalysts specific to the vanadium chemistry, e.g. Ti nanowires grown on carbon fibre. Adding channels to the electrode is a fairly simple processing step for electrode modification. There is one study in the literature that modelled the potential effect of channels in the electrode using different designs, and one other that physically added channels to the electrode, in a simple form. Both showed the method to be promising, but there lacks extensive investigation of this method, or development of optimised designs. Further to this, although a few in situ flow imaging method for the electrodes have been explored in recent years (namely thermal imaging and fluorescence microscopy) no method enables the 3D imaging required to understand flow in carbon felt.