Cost-Effective All-Copper Flow Battery Using Flowable Slurry Electrode for Large-Scale Energy Storage

One major issue limiting the implementation of renewable energy sources is the lack of efficient, cost-effective, and reliable energy storage technologies. Recently, vanadium redox flow batteries (VRFBs) have gained a significant interest as a promising electrochemical technology for large-scale energy storage due to their ability to decouple energy and power ratings and to store energy efficiently [1]. However, the high capital cost of vanadium-based electrolyte represents a major bottleneck for the commercialization of these systems [2]. By this motivation, in this study, a novel all-copper flow battery (CFB) using flowable slurry electrode is introduced. 

CFBs have a great potential for commercialization, as copper is a less toxic, widely abundant, and less expensive element than vanadium [3]. Moreover, its relatively smaller cell potential eliminates hydrogen evolution as a side reaction. However, electrochemical-plating of copper within the negative electrode during charging recouples energy and power ratings, which limits the widespread implementation of these systems. In order to mitigate this issue, a flowable slurry electrode strategy is implemented for the negative half-cell instead of using a conventional, stationary electrode [4-5]. A schematic of an all-copper flow battery using a flowable slurry electrode for the negative half-cell is shown in Fig. 1. The slurry electrode carries the deposited metal out of the stack to the reservoir, allowing the energy and power capabilities of the battery to be scaled independently.

This study is investigating the performance of a CFB using a flowable slurry electrode with a novel copper-bromide chemistry by conducting polarization curve (Fig. 2), battery cycling and efficiency analyses. As seen in Fig. 2, with the copper-bromide electrolyte and flowable slurry electrode strategy, much higher operating current densities (maximum power density of ~85 mW/cm² obtained at 200 mA/cm²) have been reached compared to literature values for an all-copper flow battery. This indicates that the slurry electrode cannot only de-couple the energy and power ratings, but can also provide an acceptable level of polarization losses.

References:

[1] A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, Q. Liu, J. Appl. Electrochem., 41, 1137-1164 (2011).

[2] R. M. Darling, K. G. Galagher, J. A. Kowalsky, S. Ha, F. R. Brushett, Energy Environ. Sci., 7, 3459-3477 (2014).

[3] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, K. Kontturi, J. Power Sources, 268, 121-128 (2014).

[4] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Power Sources, March (2015).

[5] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Electrochem. Soc., March (2015).

[5] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Electrochem. Soc., March (2015).