Vanadium redox flow cell

M. Skyllas-Kazacos, M. Richcik, R.G. Robins, A.G. Fane and M.A. Green, New allvanadium redox flow cell, J. Electrochem. Soc., 1986, 133, 1057-1058 M. Kazacos, M. Cheng, M. Skyllas-Kazacos, Vanadium redox cell electrolyte optimization studies, J. Appl. Electrochem., 1990, 20, 463 M. Skyllas-Kazacos, and F. Grossmith, Efficient vanadium redox flow cell, J. Electrochem. Soc., 1987, 134, 2950-2953. 

Skyllas-Kazacos M, Rychcik M, Robins RG, Fane AG. New all vanadium redox flow cell. J Electrochem Soc 1986 133 1057-8. 

The operational principle of a vanadium-vanadium redox flow cell (vanadium redox battery or VRB) is illustrated in Figure 12.8. 

In vanadium redox flow cells, a redox system of penta- and tetravalent vanadium ions is nsed in the positive half-cell, and a redox system of di- and trivalent vanadium ions is used in the negative half-cell. When the cell delivers charge. 

As arguably the most weU-known RFB chemistry, VRBs take advantage of the four oxidation states of vanadium within the stability window of water. This enables operation with the same element as an electroactive species as both negative and positive electrolytes and limits concerns about solution crossover and the associated permanent deleterious effects (e.g., capacity fade, irreversible side reactions). Since the initial electrochemical studies of the V(IV)A (V) and the V(II)A (III) redox couples in 1985 [48,49] and the first demonstration of an all-vanadium redox flow cell in 1986 [50] by Skyflas-Kazacos and co-workers, VRBs have been the focus of... 

M. Skyllas-Kazacos and F. Grossmith, Efficient vanadium redox flow cell, /. Electrochem. Soc.134,1987,2950-2953. 

Ferrigno et al. [65] reported the operation of a vanadium redox flow cell without using a membrane or separator. The mixing of anolyte and catho-lyte was prevented by maintaining parallel laminar flows of the electrolytes forced through a Y-shape entrance. The interface between the flow electrolytes plays the role of a separator across which ions diffuse and migrate. 

Zn-bromine flow and vanadium redox flow are special cases of secondary batteries. Here, liquid electrode materials are used on one (Zn-Br flow) or both sides (V redox flow) of the electrochemical cell. In contrast to regular batteries, which are typically completely closed systems, the liquid electrode materials in flow batteries are circulated and replenished from tanks (Figure 3.5.5). Therefore, the flow batteries possess large electrodes, the effective size of which is just limited by the volume of those tanks. This partly decouples energy and power capabilities of the batteries, allowing one to optimize both separately. 

Ferrigno R, Stroock AD, Clark TD, Mayer M, Whitesides GM (2002) Membraneless vanadium redox fuel cell using laminar flow. J Am Chem Soc 124 12930-12931... 

Most commonly, the battery will be configured with a stack of bipolar cells (10 -100 cells per stack) to give a useful output voltage and with parallel flows for the electrolytes to each of the cells in the stack. Hence, the electrodes will be bipolar with a solid core from carbon, graphite, or a carbon/polymer composite and the three-dimensional elements bonded or pressed onto either side of the solid core. The composites are a blend of a chemically stable polymer and a micron-scaled carbon powder, most commonly an activated carbon Radford et al. [127] have considered the influence of the source of the carbon and the chemical and thermal treatments on the properties of such activated carbons, especially the pore size and distribution [126]. Even though reticulated vitreous carbon has been used for the three-dimensional elements [117], the predominant materials are graphite cloths or felts with a thickness of up to 5 mm, and it is clear that such layers are essential to scale the current density and thereby achieve an acceptable power density. Details of electrode performance in the more developed flow batteries are not available but, for example, Skyllas-Kazacos et al. [124] have tabulated an overview of the development of the all vanadium redox flow battery that includes the electrode materials and the chemical and thermal treatments used to enhance activity and stability. 

Poon G (2008) Bromine complexing agents for use in vanadium bromide (V/Br) redox flow cell. The University of New South Wales... 

Aaron DS, Liu Q, Tang Z et al (2012) Dramatic performance gains in vanadium redox flow batteries through modified cell architecmre. J Power Sources 206 450-453. doi 10.1016/j. jpowsour.2011.12.026... 

Flow cells (also redox flow cells, flow batteries) are similar to batteries, except that the electrodes are catalysts for the chemical reaction, which occurs as a microporous membrane allows ions to pass from one electrolyte solution to another. Among flow cells are types that use zinc and bromine, vanadium in two types with different states, or polysulfide and bromine as the pairs of electrolytes. The advantages of flow cells are that they are capable of a large number of cycles, and the electrolytes can be replenished. 

Liquid phase reactant chemistries originally developed for redox flow batteries can be exploited to great effect in microfluidic electrochemical cells. Most commonly, vanadium redox flow battery technology utilizes soluble vanadium redox couples in both half-cells for regenerative electrochemical energy storage units [53]. The combination of aqueous redox pairs in vanadium redox cells, and VO V... 

Some improvements in anionic commercial membranes were made possible by irradiation. For example, Hwang and Ohya [133] used accelerated electron radiation to cross-link a commercial membrane based on polysulfone (New-Selemion, Asahi Glass). They proved that these highly cross-linked anion exchange membranes showed a higher coulombic and energy efficiency than Nation membranes when used in an all-vanadium redox flow battery. Application of these membranes in an alkaline fuel cell is also conceivable. 

PFSA membranes have excellent chemical inertness and mechanical integrity in a corrosive and oxidative environment, and their superior properties allowed for broad application in electrochemical devices and other fields such as superacid catalysis, gas drying or humidification, sensors, and metal-ion recovery. Here, we refer their important applications in electrochemical devices for energy storage and conversion including PEMFC, chlor-alkali production, water electrolysis, vanadium redox flow batteries, lithium-ion batteries (LIBs), and solar cells. 

Sulfonic acid groups have been also attached onto PEK backbones to be used as polymer electrolyte membranes (PEMs). Sulfonated poly(ether ketone) (SPEK) not only maintains the physical and mechanical properties of PEK itself but also provides the hydrophilicity and ion-exchange ability for electrochemical applications, such as fuel cell, vanadium redox flow battery water electrolysis, and... 

This chapter gives an overview of SPPs and derivatives for cationic fuel cell (FC) and vanadium redox flow battery (VRFB) applications. The synthesis strategies, ex situ properties, morphology, and cell performance are briefly summarized and discussed. 

This chapter will focus on the modeling of MEA and its polymer electrolyte membrane. First, 3D modeling of PEMFC and its MEA will be discussed, and an example will be put forward. Then, dynamic modeling of PEM will be introduced. Further, this chapter will move on to the fault-embedded modeling of PEM. As an extension, application of membranes in other cases will be recommended, such as in lithium battery, vanadium redox flow battery (VRFB), chlor-alkali electrolysis, water electrolysis, and solar cell. Finally, several typical examples will be given, including Pt and Pt alloy simulation with density functional theory (DFT), water formation and Pt adsorption on carbon reactive force field (ReaxFF) simulation, and coarse-grained simulations. 

The assembly of (a) single cell, (b) multiple cells and (c) cell stack. (X.F. Li et aL, Ion exchange membranes for vanadium redox flow battery (VRB) applications. Energy Environ. Sci. 4, 2011, 1147-1160. Copyright 2011. Reprinted with permission from Royal Society of Chemistry.)... 

Physical Properties of Negative Half-Cell Electrolytes in the Vanadium Redox Flow Battery... 

See colour insert.) Photograph of an all-vanadium redox flow battery showing the electrolyte reservoirs that store the two half-ceU solutions that are pumped through the cell stack where energy is generated by the electrochemical reactions of the vanadium redox couples at inert electrodes. 

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