• Journal of the Korean Chemical Society
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• v.68 no.1
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• pp.9-11
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• 2024

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.12
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• pp.769-776
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• 2016

In this study, a numerical simulation of a vanadium redox flow battery was investigated for reactions involving an electrochemical species using comprehensive conservation laws and a kinetic model. For a 3-D geometry of the cell, the distributions of electric potential, vanadium concentration, overpotential, and ohmic loss were calculated. The cell temperature and initial vanadium ion concentration were set as variables. The voltage and electrochemical loss were calculated for each variable. The effects of each variable's impact on the electrochemical performance of a vanadium redox flow battery was numerically analyzed using the calculated overpotential in the electrode and the ohmic loss in the electrolyte phase. The cell temperature increased from $20^{\circ}C$ to $80^{\circ}C$ when the voltage efficiency decreased from 89.34% to 87.29%. The voltage efficiency increased from 88.65% to 89.25% when the vanadium concentration was changed from $1500mol/m^3$ to $3000mol/m^3$.

• 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.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.330-338
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• 2021

An integral electrode-bipolar plate assembly, which is composed of electrode, conductive adhesive film (CAF) and bipolar plate, has been developed and evaluated for application with a vanadium redox flow battery (VRB) to decrease contact resistance between electrode and bipolar plate. The CAF, made of EVA (ethylene-vinyl-acetate) material with carbon black or CNT (Carbon Nano Tube), is applied between the electrode and the bipolar plate to enable an integral assembly by adhesion. In order to evaluate the integral assembly of VRB by adhesive film, the resistivity of integral assembly and the performance of single cell were investigated. Thus, it was verified that the integral assembly is applicable to redox flow battery. Through resistance and contact resistance of bare EVA and CAF films on bipolar plate were changed. Among the adhesive films, CAF film coated with carbon black showed the lowest value in through resistance, and CAF film coated with CNT showed the lowest value in contact resistance, respectively. The efficiency of VRB single cell was improved by applying CAF films coated with carbon black and CNT, resulting in the reduced overvoltage in charging process. Therefore, the energy efficiency of both CAF films, about 84%, were improved than that of blank cell, about 79.5 % under current density at 40 mA cm^-2. The energy efficiency of the two cells were similar, but carbon black coated CAF improved the coulomb efficiency and CNT coated CAF improved the voltage efficiency, respectively.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.175-179
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• 2023

Herein we present a tested aqueous based redox flow battery (RFB) that employs phosphomolybdic acid and ferrocyanide as the negative and positive active species in an aqueous sodium hydroxide solution. The different concentrations of NaOH solution, such as 1.0, 1.2, 1.4, 1.5, and 1.6 M, were prepared for checking the electrochemical properties and stability. The NaOH concentration as a supporting electrolyte in the negative species appears to play an important role in the electrochemical properties of phosphomolybdic acid. Moreover, the optimum value of the concentration is necessary for the best performance. The resistance of the electrolyte decreased with increasing the concentration up to 1.5 M and then increased to 1.6 M. Hence, the decrease in electrolyte resistance appears to greatly influence the energy efficiency, which is improved by increasing the concentration of NaOH. In addition, the 1.5 M NaOH solution appears to be the concentration required for optimum performance.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.99-110
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• 2013

Redox flow batteries are attractive energy-storage devices for renewable energy and peak-power energy control. Even though some prototypes are available already, many new materials are under development for new battery systems. In this reports, redox pairs and theirs properties are explained, by which one can understand issues with redox pairs, such as contaminations, cross-over, ionic selectivity, and solubility. Batteries that have the same redox pairs in both electrode compartments can be operated longer than those with different redox pairs due to the prevention form the cross-contamination. There are undivided redox flow batteries that have no membrane, which is another direction improving cycle life of the batteries.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.240-248
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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 range of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. Among consisting elements of the VRFB, the ion exchange membrane and the electrode play important roles. In this study, carbon PVC coposite sheets for the VRFB have been developed and electrochemical characteristics investigated. Current collector for VRFB, carbon PVC composite sheets (CPCS), were prepared with G-1028 as a conducting particle, PVC as a polymer, Dibutyl phthalate (DBP) as a plasticizer and fumed Silica (FS) as a dispersion agent. CPCS has been shown to have the characteristics as an excellent current collector for VRFB and electrochemical properties of specific resistivity 0.31 ${\Omega}cm$, which were composed of G-1028 80 wt%, PVC 10 wt%, DBP 5 wt% and FS 5 wt%.

• Journal of the Korean Electrochemical Society
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• v.21 no.1
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• pp.1-5
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• 2018

In this study, boron - doped carbon was prepared by reducing carbon dioxide ($CO_2$) at high temperature by using sodium borohydride ($NaBH_4$). The boron - doped carbon was coated on carbon felt and applied as an electrode for a vanadium redox battery cell. As a result of electrochemical performance evaluation, reversibility of carbon felt coated with boron doped carbon compared to pure carbon felt was improved by about 20% and charge transfer resistance was reduced by 60%. In the charge / discharge results, energy density and energy efficiency were improved by 21% and 12.4%, respectively. These results show that carbon produced by reduction of $CO_2$ can be used as electrode material for redox flow battery.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.61-67
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• 2018

High-power lithium batteries are suitable for equipment with high power output needs, such as for ESS's initial start-up. However, their management cost is increased by the installation of air-conditioning to minimize the risk of explosion due to internal temperature rise and also by a restriction on the number of charge/discharge cycles. High-capacity flow batteries, on the other hand, have many advantages. They can be used for over 20 years due to their low management costs, resulting from no risk of explosion and a high number of charge/discharge cycles. In this paper, we propose an ESS based on hybrid batteries that uses a lithium iron phosphate battery (LiFePO) at the initial startup and a vanadium redox flow battery (VRFB) from the end of the transient period, with a bi-directional PCS to operate two batteries with different DC voltage levels and using an efficient energy management control algorithm.