Distributed Diagnostic Techniques to Quantify Spatial and Temporal Voltage Gradients in Energy Storage Systems Utilizing Flowable Electrodes
In this study, we have developed a distributed diagnostics approach which enables us to resolve the localized voltage within the cell under various conditions. To accomplish this, special electrode arrays were manufactured which allowed us to precisely locate voltage probes within the cell. These electrode arrays were installed in a working cell, and real-time data was collected during potentiostatic charge/discharge operation under a variety of flow conditions. For this study, we applied this distributed diagnostic technique to an electrochemical flow capacitor (EFC) system, but the technique can be readily adapted to other flowable electrode systems as well.
From the spatially-resolved voltage profiles, we observed a significant voltage drop across the current-collector|electrode interface under static (no-flow) conditions. During flowing operation, the total voltage drop across the current-collector|electrode interface is slightly reduced, while the voltage drop within the bulk of the electrode increases significantly. As a result, the material furthest from the current-collectors is not well utilized, giving rise to reduced system capacity and efficiency. These results indicate a strong coupling between flow conditions and charge percolation within the electrodes, and provides guidance for the optimization of flowable electrodes and the design of flow cells.
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