Degradation of Electrode Materials in Vanadium Redox Flow Batteries

Recent works in vanadium redox flow batteries (VRFBs) have been successful in improving the energy density by increasing vanadium solubility in the electrolyte¹ and achieving high power density through electrode modification, membrane selection, and superior cell design ^2,3. These accomplishments lead to significant reduction of the system cost and therefore enhance the economic attractiveness of VRFB technology.

To achieve market implementation, the large-scale energy storage system requires a balance between performance, cost, and durability. While power and energy densities have been recently improved, the investigation of component durability, which is equally important, has yet to be reported in significant detail.

In this work, we demonstrate an approach to study the electrode degradation in single-cell VRFBs.

Ex-situ electrolyte soaking experiments were used to determine conditions under which the electrodes degrade, and the extent of the degradation. Several techniques were adopted to characterize property changes in the degraded materials. Various carbon materials were investigated to determine viable candidates and characteristics required for long-term use in VRFB systems.

Additionally, in-situ cycling tests of various carbon materials have been carried out to illustrate the relationship between material degradation and cell performance decay. Declines in performance (Fig. 1) are monitored and correlated to changes in the material properties. Modification of the cycling parameters reveals operating conditions leading to the most severe decay in the carbon material, so that accelerated degradation protocols can be developed for evaluation of additional materials.

References

1. L. Li, S. Kim, W. Wang, M. Vijayakumar, Z. Nie, B. Chen, J. Zhang, G. Xia, J. Hu, G. Graff, J. Liu, Z. Yang, Adv. Energy Mater., 1, 394, (2011). 

2.  Q. H. Liu, G. M. Grim, A. B. Papandrew, A. Turhan, T. A. Zawodzinski, M. M. Mench, J. Electrochem. Soc., 159, A1246, (2012).

3. D.S. Aaron, Q. Liu, Z. Tang, G.M. Grim, A.B. Papandrew, A. Turhan, T.A. Zawodzinski, M.M. Mench, J. Power Sources, 206, 450, (2012).

4. M. Zhang, M. Moore, J.S. Watzon, T.A. Zawodzinski, R.M. Counce, J. Electrochem. Soc., 159, A1183, (2012).