Battery vanadium redox

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. 

Redox flow batteries, under development since the early 1970s, are stUl of interest primarily for utility load leveling applications (77). Such a battery is shown schematically in Figure 5. Unlike other batteries, the active materials are not contained within the battery itself but are stored in separate tanks. The reactants each flow into a half-ceU separated one from the other by a selective membrane. An oxidation and reduction electrochemical reaction occurs in each half-ceU to generate current. Examples of this technology include the iron—chromium, Fe—Cr, battery (79) and the vanadium redox cell (80). 

One of the most important requirements that must be met is the membrane s ability to prevent excessive transfer of water from one half cell to the other. The preferential transfer of water can be a problem in the vanadium battery as one half-cell (the negative half cell in the case of cation exchange membranes) is flooded and becomes diluted, while the other becomes more concentrated, adversely affecting the overall operation of the cell. Most of the membranes show good initial water transfer properties, but their performance deteriorates with exposure to the vanadium solutions. Sukkar et al. ° evaluated various polyelectrolytes to determine whether they could improve the selectivity and stability of the membranes in the vanadium redox cell solutions. Both the cationic and anionic polyelectrolytes evaluated improved the water transfer properties of the membranes, although upon extended exposure to the vanadium electrolyte the modified membranes did not maintain their improved water transfer properties. The solvent based Nuosperse 657 modified membrane displayed exceptional properties initially but also failed to maintain its performance with extended exposure to the vanadium solutions. 

A ubiquitous characteristic of vanadium chemistry is the fact that vanadium and many of its complexes readily enter into redox reactions. Adjustment of pH, concentration, and even temperature have often been employed in order to extend or maintain system integrity of a specific oxidation state. On the other hand, deliberate attempts to use redox properties, particularly in catalytic reactions, have been highly successful. Vanadium redox has also been successfully utilized in development of a redox battery. This battery employs the V(V)/V(IV) and V(III)AT(II) redox couples in 2.5 M sulfuric acid as the positive and negative half-cell electrolytes, respectively. Scheme 12.2 gives a representation of the battery. The vanadium components in both redox cells are prepared from vanadium pentoxide. There are two charge-discharge reactions occurring in the vanadium redox cells, as indicated in Equation 12.1 and Equation 12.2. The thermodynamics of the redox reactions involved have been extensively studied [8],... 

Heintz, A. and Ch. Illenberger. 1998. Thermodynamics of vanadium redox flow batteries Electrochemical and calorimetric investigations. Ber. Bunsenges. Phys. Chem. 102 1401-1409. 

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. 

New perspectives arising from isothermal oxidation. The next chapter of this book describes the greatly altered perspective of the fuel cell industry, when Grove s ideas are updated. The second chapter describes the detail of Regenesys, or ESS-RGN. This system has changed hands, as noted above, and information is available from http //www.vrbpower.com/. (The initials VRB stand for Vanadium Redox Battery, a low-power alternative to Regenesys.) The new 2005 VRB Power Systems shorthand is ESS-VRB for 2.5 to 10 MW and ESS-RGN for 10 to 100 MW. In Chapter 2 the reader will be acquainted with ESS-RGN, one of the two VRB fuel cell systems (incompressible liquid based) which can be termed complete . The redox battery uses small pumps as circulators. 

Other battery systems that have been suggested for use in RAPS facilities include zinc-bromine [7], vanadium redox [8], and aluminium-air [9]. It is considered unlikely, however, that these systems will be used in mainstream RAPS applications as their cost is still significantly higher than that of lead-acid alternatives, and their long-term reliability has yet to be proven. 

Because vanadium ions exist in four different oxidation states (as V2+, V3+, V02+ and V02+) in aqueous solution, redox couples can be formed by all vanadium ions. The emf of a vanadium redox battery is 1.4 V and the electrode kinetics are higher than those of the Fe-Cr battery. Also, the energy density of the battery can be increased due to the high solubility of vanadium salts.257 In the battery, vanadium sulfate solution is used,... 

G.-J. Hwang and H. Ohya, Cross-linking of anion exchange membrane by accelerated electron radiation as a separator for all-vanadium redox flow battery, J. Membr. Sci., 1997, 132, 55-61. 

Depending on the final application of carbon materials, very different properties and structures on different length scales need to be analyzed in detail using the aforementioned methods and, most favorably, a combination of them. A systematic Raman, TEM, SEM, NEXAFS, and EPR study of various carbon materials for impregnation into carbon felts used as positive electrode in all-vanadium redox flow batteries is given by Melke et al. [14]. 

Melke, J., Jakes, P, Langner, J., Riekehr, L., Kunz, U, Zhao-Karger, Z., Nefedov, A., Sezen, H., Woll, C., Ehrenberg, H., and Roth, C. (2014) Carbon materials for the positive electrode in all-vanadium redox flow batteries. Carbon, 78, 220- 230. 

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. 

Rychick M, Skyllas-Kazacos M (1988) Characteristics of new all-vanadium redox flow battery. J Power Sources 22 59-67... 

Parasuraman A, Lim TM, Menictas C, Skyllas-Kazacos M (2013) Review of material research and development for vanadium redox flow battery applications. Electrochim Acta 101 27-40. doi 10.1016/j. electacta.2012.09.067... 

Kear G, Shah AA, Walsh FC (2012) Development of the all-vanadium redox flow battery for energy storage a review of technological, flnancial and policy aspects. Int J Energy Res 36 1105-1120. doi 10.1002/er.l863... 

Huang K-L, Li X, Liu S et al (2008) Research pogiess of vanadium redox flow battery for energy storage in China. Renew Energy 33 186-192. doi 10.1016/j.ienene.2007.05.025... 

Xiangguo T, Jicui D, Jing S (2014) Effects of diffeaent kinds of surfactants on Nafion membranes for all vanadium redox flow battery. J Solid State Electrochem. doi 10.1007/ S10008-014-2713-7... 

Skyllas-Kazacos M, Kazacos M (2011) State of charge monitoring methods for vanadium redox flow battery control. J Power Sources 196 8822-8827. doi 10.1016/j.jpowsour.2011.06. 080... 

Wang WH, Wang XD (2007) Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery. Electrochim Acta 52 6755-6762. doi 10.1016/j. electacta.2007.04.121... 

Al-Fetlawi H, Shah AA, Walsh FC (2010) Modelling the effects of oxygen evolution in the all-vanadium redox flow battery. Electrochim Acta 55 3192-3205. doi 10.1016/j.electacta. 

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... 

Blanc C, Rufer A (2008) Multiphysics and energetic modeling of a vanadium redox flow battery. 2008 IEEE International Conference on Sustainable Energy Technologies. IEEE, Singapore, pp 696-701... 

Flow cells are ideal for stors e systems in remote locations. Vanadium redox systems, for instance, deliver up to 500 kW for up to ten hours. Zinc-bromine systems have been produced for 50-kWh and 500-kWh systems to reinforce weak distribution networks or prevent power fluctuations. Hydrogen fuel cells can potentially do almost anything a battery can do provide backup power, perform power leveling, run handheld devices, and supply primary or auxiliary power to cars, trucks, buses, and boats. In many cases they are more efficient than petrochemical fuels. A hydrogen fuel cell in a vehicle that uses an electric motor, for example, can be 40 to 60 percent efficient, compared with the 35 percent peak efficiency of the internal combustion engine. 

Based on their early fundamental research of all-VRFBs, Skyllas-Kazacos et al. [25] also first developed some commercial products, for example, a 1 kW vanadium redox battery (VRB) cell stack. By employing 1.5-2 M vanadium sulphate, sulphuric acid in both half-cells, over 85% of theoretical capacity and 70-80% energy efficiency was obtained. Then in 1994, a 4 kW/12 kWh vanadium battery was evaluated in a demonstration solar house by Thai Gypsum Products Ltd. in Thailand under a license lirom the UNSW [26]. 

Li X, Zhang HM, Mai ZS, Zhang HZ, Vankelecom I. Ion exchange membranes for vanadium redox flow battery (VRB) applications. Energy Environ Sci 2011 4 1147-60. 

Skyllas-Kazacos M, Peng C, Cheng M. Evaluation of precipitation inhibitors for supersaturated vanadyl electrol3des for the vanadium redox battery. Electrochem Solid-State Lett 1999 2 121-2. 

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