Vanadium Flow Battery Performance Improvement through Electrode Modification

Flow battery performance has recently been significantly improved through the use of carbon papers, adopting a so-called “zero-gap” architecture.[1] The benefits of the carbon paper, as opposed to carbon felt, are increased rigidity for reduced contact resistance, high surface area, and low compression. These combinations lead to an improved flow through the high surface area electrode, and enhanced high current performance through increased mass transport.

Much attention has been devoted to improving the V(IV)-V(V) couple at the positive electrode.[2] However, a need exists to increase the reversibility of the vanadium reactions at the negative electrode. For example, Aaron et al. have demonstrated[3] that on discharge, V(II) oxidation appears to have slower kinetics than V(V) reduction, resulting in high overpotentials at the negative electrode. Therefore, in addition to the improvements gained by the use of carbon paper, increased performance may be obtained through increasing the oxidation kinetics of the negative electrode. This paper will demonstrate some efforts aimed at reducing the discharge overpotentials at the negative electrode through electro-deposition of metals.

 An all-vanadium cell was utilized in these tests, with single-carbon papers used as electrodes. For all tests, a fresh carbon paper was utilized at the positive electrode, while the negative electrode was either plain carbon paper, or metal-coated carbon paper. The results indicate that performance of the cell improved dramatically by adding metal to the surface of the negative electrode.

 This presentation will discuss the approach employed herein for improved performance, as well as its limitations.

[1] 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 (2012) 4-4.

[2] C. Flox, M. Skoumal, J. Rubio-Garcia, T. Andreu, J.R. Morante, Appl Energ, 109 (2013) 344-351.

[3] D. Aaron, C.N. Sun, M. Bright, A.B. Papandrew, M.M. Mench, T.A. Zawodzinski, Ecs Electrochem Lett, 2 (2013) A29-A31.