Effect of Interdigitated Flow Field Geometry on Redox Flow Cell Performance

Monday, 29 May 2017: 10:20
Grand Salon B - Section 12 (Hilton New Orleans Riverside)
M. R. Gerhardt, A. A. Wong, and M. J. Aziz (Harvard School of Engineering and Applied Sciences)
A large fraction of the cost of a flow battery installation comes from the high cost of separators and bipolar plates1. Optimizing the use of active area in flow batteries by maximizing power density allows cell stack engineers to reduce the amount of stack materials required. The design of flow fields has a significant impact on cell performance, including peak galvanic power density2,3. In this work, we present an experimental and computational study of interdigitated flow fields with varying dimensions. We demonstrate reduction of resistive and mass transport overpotential losses by altering the interdigitated flow field dimensions to reduce zones of mid-channel stagnant flow within the porous electrode. A two-dimensional model of an interdigitated flow field, coupling fluid dynamics and electrochemistry, is used to guide optimization of the channel, land, and electrode dimensions in the flow field.

To study the influence of mass transport on performance, a flow cell is assembled with an unstructured, flow-through porous electrode, with a flat plate replacing the interdigitated flow field. Even with this simplified flow field, discrepancies persist between observed experimental results and predictions from porous electrode theory. We report our progress toward understanding and resolving these discrepancies.

1. V. Viswanathan et al., J. Power Sources, 247, 1040–1051 (2014)

2. M. L. Perry, R. M. Darling, and R. Zaffou, ECS Trans., 53, 7–16 (2013)

3. R. M. Darling and M. L. Perry, J. Electrochem. Soc., 161, A1381–A1387 (2014)

Figure 1. Experimental results and computational predictions of overvoltages from a symmetric potassium ferrocyanide/ferricyanide flow cell using one of four different flow fields. The cell consists of one sheet of SGL 39-AA on each side of a Nafion 212 membrane. The active area of each flow field is 5 cm2.