A porous carbon electrode fully saturated with electrolyte is one crucial aspect of vanadium redox flow battery efficiency. It determines the electrochemically active surface area, provides more active sites for the reaction during operation, and prevents local degradation due to inhomogeneities in electrolyte distribution. We investigate the electrolyte invasion and distribution at open-circuit potential in heat-treated carbon felt electrodes at varying compression ratios and flow field configurations, using synchrotron X-ray radiography. The quantitative analysis yields time-resolved saturation values of the injection and resolves local changes in saturation to detect areas of lower electrolyte accessibility. Compression ratios of 50% and above lead to a high electrode utilization with more than 97% saturation over the felt thickness. In contrast, carbon felts at 25% and 17% compression only reach 49% and 15% saturation near the flow fields. However, increasing the flow velocity after the injection causes the boundary area next to the flow field to fill even at low compressions. This area is especially critical for the electrode utilization since it is invaded after the bulk. Depending on the compression level, it does not reach full saturation.

完全充满电解质的多孔碳电极是钒氧化还原液流电池效率的关键方面。它确定电化学活性的表面积，为操作过程中的反应提供更多的活性部位，并防止由于电解质分布不均匀而引起的局部降解。我们使用同步加速器X射线射线照相技术研究了在不同压缩比和流场配置下，经过热处理的碳毡电极在开路电势下电解液的侵入和分布。定量分析产生了时间分辨的进样饱和度值，并解决了饱和度的局部变化，以检测电解液可及性较低的区域。压缩比为50％或更高会导致电极利用率高，并且在毛毯厚度上的饱和度超过97％。相比之下，碳毡在25％和17％压缩时仅在流场附近达到49％和15％的饱和度。但是，即使在低压缩下，注入后提高流速也会导致流场附近的边界区域充满。该区域对于电极的利用尤其重要，因为它是在散装之后侵入的。根据压缩级别，它不会达到完全饱和。