• Membrane Journal
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• v.19 no.2
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• pp.129-135
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• 2009

The cation exchange membrane using the block co-polymer of polysulfone and polyphenylenesulfidesulfone was prepared for a separator of all-vanadium redox flow battery. The membrane property of the prepared cation exchange membrane was measured. The thermal stability of the prepared cation exchange analyzed by TG showed a more stable than that of Nafion117. The lowest measured membrane resistance, equilibrated in 1mol/L $H_2SO_4$ aqueous solution, $0.96{\cdot}cm^2$ at 3 cc of CSA (chlorosulfuricacid) which was introduction agent of ion exchange group. Electrochemical property of all-vanadium redox flow battery using the prepared cation exchange membrane was measured. Electromotive force in 100% of state of charge was 1.4 V which was that of all-vanadium redox flow battery, and cell resistance in charge and discharge at each state of charge had a low value compared with that of all-vanadium redox flow battery using Nafion117.

• Polymer(Korea)
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• v.35 no.6
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• pp.586-592
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• 2011

In this study, we synthesized vinylbenzyl chloride-co-styrene-co hydroxyethyl acrylate (VBC-co-St-co-HEA) copolymer that can be applied to redox the flow battery process. The anion exchange membrane was prepared by the amination and crosslinking of VBC-co-St-co-HEA copolymer. The chemical structure and thermal properties of VBC-co-St-co-HEA copolymer and aminated VBC-co-St-co-HEA(AVSH) membrane were characterized by FTIR, $^1H$ NMR, TGA, and GPC analysis. The membrane properties such as ion exchange capacity(IEC), electrical resistance, ion conductivity and efficiency of all-vanadium redox flow battery were measured. The IEC value, electrical resistance, and ion conductivity were 1.17 meq/g, $1.9{\Omega}{\cdot}cm^2$, 0.009 S/cm, respectively. The charge-discharge efficiency, voltage efficiency and energy efficiency from all-vanadium redox flow battery test were 99.5, 72.6 and 72.1%, respectively.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.721-727
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• 2011

All vanadium redox-flow battery (VRFB) has been studied actively as one of the most promising electrochemical energy storage systems for a wide rage of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. In this study, carbon felt electrodes were treated by electrochemical oxidation with KOH, and the cyclic voltammetry were studied in order to investigate redox reactivity of vanadium ion species with carbon felt electrodes. Besides the effect of electrochemical oxidation on the surface chemistry of carbon felt electrodes were investigated using the X-ray photoelectron spectroscopy (XPS). After electrochemical oxidation, XPS analysis of PAN based GF20-3 carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after electrochemical oxidation. Redox reaction characteristics using cyclic voltammetry (CV) were ascertained that the electrochemical treated electrode were more reversible than the untreated electrode.

• Journal of Hydrogen and New Energy
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• v.26 no.4
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• pp.324-330
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• 2015

The electrolyte flow rates of vanadium redox flow battery play very important role in terms of ion transfer to electrolyte, kinetics and pump efficiency in system. In this paper a vanadium redox flow battery single cell was tested to suggest the optimization criteria of electrolyte flow rates on the efficiencies. The compared electrolyte circulation flow rates in this experimental work were 15, 30 and 45 mL/min. The charge/discharge characteristics of the flow rate of 30 mL/min was the best out of all flow rates in terms of charging and discharging time. The current efficiencies, voltage efficiencies and energy efficiencies at the flow rate of 30 mL/min were the best. The IR losses obtained at thd current density of $40mA/cm^2$, at the flow rates of 15, 30 and 45 mL/min were 0.085 V, 0.042 V and 0.115 V, respectively. The charge efficiencies at the current density of $40mA/cm^2$ were 96.42%, 96.45% and 96.29% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The voltge efficiencies at the current density of $40mA/cm^2$ were 77.34%, 80.62% and 76.10% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. Finally, the energy efficiencies at the current density of $40mA/cm^2$ were 74.57%, 77.76% and 73.27% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The optimum flow rates of electrolytes were 20 mL/min in most of operating variables of vanadium redox flow battery.

• Journal of the Korean Electrochemical Society
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• v.16 no.4
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• pp.204-210
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• 2013

Thin pore-filled cation and anion-exchange membranes (PFCEM and PFAEMs, $t_m=25-30{\mu}m$) were prepared using a porous polymeric substrate for efficient all-vanadium redox flow battery (VRB). The electrochemical and charge-discharge performances of the membranes have been systematically investigated and compared with those of commercially available ion-exchange membranes. The pore-filled membranes were shown to have higher permselectivity as well as lower electrical resistances than those of the commercial membranes. In addition, the VRBs employing the pore-filled membranes exhibited the respectable charge-discharge performances, showing the energy efficiencies (EE) of 82.4% and 84.9% for the PFCEM and PFAEM, respectively (cf. EE = 87.2% for Nafion 1135). The results demonstrated that the pore-filled ion-exchange membranes could be successfully used in VRBs as an efficient separator by replacing expensive Nafion membrane.

• Journal of ILASS-Korea
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• v.22 no.2
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• pp.69-79
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• 2017

When designing a redox flow battery system, compression of battery stack is required to prevent leakage of electrolyte and to reduce contact resistance between cell components. In addition, stack compression leads to deformation of the porous carbon electrode, which results in lower porosity and smaller cross-sectional area for electrolyte flow. In this paper, we investigate the effects of electrode compression on the cell performance by applying multi-dimensional, transient model of all-vanadium redox flow battery (VRFB). Simulation result reveals that large compression leads to greater pressure drop throughout the electrodes, which requires large pumping power to circulate electrolyte while lowered ohmic resistance results in better power capability of the battery. Also, cell compression results in imbalance between anolyte and catholyte and convective crossover of vanadium ions through the separator due to large pressure difference between negative and positive electrodes. Although it is predicted that the battery power is quickly improved due to the reduced ohmic resistance, the capacity decay of the battery is accelerated in the long term operation when the battery cell is compressed. Therefore, it is important to optimize the battery performance by taking trade-off between power and capacity when designing VRFB system.

• Journal of Hydrogen and New Energy
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• v.28 no.2
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• pp.200-205
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• 2017

The three electrodes (carbon felt) were tested in all-vanadium redox flow battery (VRFB) to confirm the its usefulness. The electrode property was measured by the CV (cyclic voltammetry) method. The current ratio of maximum peak(IPA/IPC) in GF040BH5 and GF051BH3 had almost the same value compared to that in XF30A. The performances of VRFB using the each electrode were measured during 5 cycles of charge-discharge at the current density of $60mA/cm^2$. An average energy efficiency of the VRFB was 77.8%, 77.3%, and 79.2% for XF30A, GF040BH5 and GF051BH3, respectively. It was confirmed from the data that GF040BH5 and GF051BH3 is well suited for use in a VRFB as a electrode, like XF30A.

• Membrane Journal
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• v.21 no.2
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• pp.107-117
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• 2011

The all vanadium redox-flow battery (V-RFB) is investigating as one of large-scale power storage systems. Particularly, V-RFB is being investigated as one of the power storage systems for the load leveling and output power equalization of the power systems using renewable energy such as solar and wind. In this paper, it was explained for the principle and construction, recent research review, economy, element technology in V-RFB.

• Journal of Hydrogen and New Energy
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• v.28 no.5
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• pp.531-535
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• 2017

The performance of all-vanadium redox flow battery (VRFB) was tested with an increase of the current density. APS membrane (anion exchange membrane) and GF050CH (cabon felt) were used as a separator and electrode, respectively. An average energy efficiency of the VRFB was 79.5%, 68.1%, and 62.8% for the current density of $60mA/cm^2$, $120mA/cm^2$, and $160mA/cm^2$, respectively. It was confirmed that VRFB can be used as a energy storage system at the higher current density even if the energy efficiency was deceased about 21%.

• Membrane Journal
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• v.21 no.2
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• pp.141-147
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• 2011

The cation exchange membrane using TPA (tungstophosphoric acid) and the block co-polymer of polysulfone and polyphenylenesulfidesulfone was prepared for a separator of all-vanadium redox flow battery. The membrane resistance of the prepared cation exchange membrane in 1mol/L $H_2SO_4$ aqueous solution was measured. The membrane resistance of the prepared Psf-PPSS and Psf-TPA-PPSS cation exchange membrane was about $0.94{\Omega}{\cdot}cm^2$. Electrochemical property of all-vanadium redox flow battery using the prepared cation exchange membrane was measured. The measured charge-discharge cell resistance of V-RFB at 4 A decreased in the order; Nafion117 < Psf-TPA-PPSS < Psf-PPSS. The durability of membrane was earried out by soaking it in $VO_2{^+}$ solution and evaluated by measuring the charge-discharge cell resistance of V-RFB with an increase of soaking time. The prepared Psf-PPSS cation exchange membrane had high durability and Psf-TPA-PPSS cation exchange membrane had almost same durability compared with Nafion117.