• Membrane Journal
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• v.30 no.5
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• pp.307-318
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• 2020

Conventional perfluorinated sulfonic acid membrane, Nafion is widely used for vanadium redox flow battery (VRFB). It is desired to prevent vanadium ion permeation through a membrane to retain the capacity, and to keep the cell efficiency of a VRFB. Highly proton conductive and chemically stable Nafion membranes, however, suffer from high vanadium permeation, which induce the reduction in charge and discharge capacity by side reactions of vanadium ions. In this study, to resolve the issue, silica nanoparticles, which are functionalized with 3-aminopropyl group (fS) are introduced to enhance the long-term performance of a VRFB by lowering vanadium permeation. It is expected that amine groups on silica nanoparticles are converted to positive ammonium ion, which could deteriorate positively charged vanadium ions' crossover by Gibbs-Donnan effect. There is reduction in proton conductivity may due to acid-base complexation between fS and Nafion side chains, but ion selectivity of proton to vanadium ion is enhanced by introducing fS to Nafion membranes. With the composite membranes of Nafion and fS, VRFBs maintain their discharge capacity up to 80% at a high current density of 150 mA/㎠ during 200 cycles.

• 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 the Korean Electrochemical Society
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• v.19 no.1
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• pp.21-27
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• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.231-233
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• 2018

바나듐 산화 환원 유동 배터리는 긴 수명주기와 높은 에너지효율로 리튬 이온 배터리를 대체할 차세대 배터리로 주목받고 있다. 에너지가 저장되는 전해질을 순환시키면서 충전 과방전이 이루어진다는 이차전지 인 만큼 유지 보수 비용을 획기적으로 절감할 수 있고 사용자의 요구조건에 따라 출력과 에너지 용량을 매우 쉽게 조절할 수 있다는 장점이 있다. 하지만, 바나듐 산화 환원 유동 배터리를 다양한 어플리케이션에 적용하기 위하여 바나듐 배터리 운용에서 여러 가지 요소들을 고려하여야 한다. 본 논문에서는 충전 및 방전을 지속했을 때의 용량 감소하는 바나듐 산화 환원 유동 배터리의 특성을 고려하여 가장 까다로운 문제 중 하나인 휴지 기간에서의 자가 방전에 대해 온도와 SOC에 따라 특성 분석을 실시하였다.

• Membrane Journal
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• v.31 no.4
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• pp.262-267
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• 2021

The electrochemical performance of all vanadium redox flow battery (VRFB) using an electrolyte prepared from ammonium metavanadate and a cation exchange membrane (Nafion117) was evaluated. The electrochemical performance of VRFB was measured at a current density of 60 mA/cm². The average current efficiency of VRFB using the electrolyte prepared from ammonium metavanadate was 94.9%, the average voltage efficiency was 82.2%, and the average energy efficiency was 78.0%. In addition, it was confirmed that the efficiencies of VRFB using the electrolyte prepared from ammonium metavanadate had almost the same value as the efficiencies of VRFB using the electrolyte prepared with vanadyl sulfate (VOSO₄).

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.123-126
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• 2002

레독스-흐름 2차 전지는 레독스 쌍이 녹아있는 수용액을 탱크에 저장한 다음 펌프로 유통형 전해 셀에 공급해 충방전하는 2차 전지의 한 종류이며, 종래의 2차 전지와는 다른 재생형 연료전지 중의 하나이다[1]. 이러한 전지의 원리는 19세기말부터 알려져 있었지만, 중량과 용적이 컸기 때문에 소형화, 경량화가 중시되는 2차 전지로서는 부적당하였고, 수용액을 사용하기 때문에 기전력이 낮다는 결점이 있었다.(중략)

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.94-102
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• 2014

Cation exchange membrane (Nafion) was modified to reduce the vanadium ion permeation through the membrane and to increase the vanadium redox flow battery (VRB) system performance by coating the graphene oxide (GO) which has nano-plate like morphology. Modified membrane properties were studied by measuring the ion exchange capacity (I.E.C), water uptake and proton conductivity. The thickness of the coated layer on the surface of the Nafion membrane was observed as $0.93{\mu}m$ by SEM. Proton conductivity and vanadium ion permeability of the modified membrane were decreased to 27% and 25% compared to that of the commercial Nafion membrane respectively. VRB single cell performance test was performed to compare the system performance of the VRB applied with commercial Nafion membrane and modified membrane. VRB system applied with modified membrane showed higher coulombic efficiency and energy efficiency than the VRB system applied with the commercial Nafion membrane due to the reduction of the vanadium ion permeation. From these result, we could suggest that the membrane modification by coating the GO on the surface of the Nafion membrane could be one of the promising strategies to reduce the vanadium ion permeation and to increase the VRB system performance effectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.589-594
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• 2014

Recently, higher capacity and energy density of lithium ion batteries are increasingly demanded for enhancing their performance in view of the rise in the commercial distribution of electric and hybrid vehicles. Computational analysis of a porous structure of vanadium pentoxide cathode was performed, employing a phase field model. The incipient model was designed as a spherical structure with cylindrical-shaped pores. Modifying the diameters and lengths of the pore cylinder and the number of pores, we considered different conditions for the porous vanadium pentoxide cathodes for analyzing their effect on the amount of lithium ion intercalated to them. Subsequently, we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.671-676
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• 2013

Recently, there are many efforts focused on development of Redox Flow Battery (RFB) for large energy storage system. Economical hydrocarbon membranes alternative to fluorinated membranes for RFB membrane are receiving attention. In this study, characteristics of poly(arylene ether sulfone) (PAES) were compared with expensive fluorinated membrane at VRB (Vanadium Redox Flow Battery) operation condition. Permeability of vanadium ion through membrane, ion exchange capacity (IEC), change of OCV, swelling, charge-discharge curves and energy efficiency were measured. PAES membrane showed lower permeability of vanadium ion, higher IEC and then higher energy efficiency compared with Nafion 117 membranes.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.10a
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• pp.63-64
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• 1993

레독스-흐름 2차전지는 발전소의 잉여전력, 태양전지 및 전기자동차 등 응용 분야가 넓은 유망한 에너지 저장 방법의 하나이다[1,2]. Fe-Cr계 2차전지와 비교하여 수소 가스의 발생이 없고 양쪽 액의 확산에의한 혼합으로 전지의 용량이 떨어지지 않고 rebalance의 필요가 없는 등 많은 장점을 가지고 있으며 조작이 간단하며 기전력 (1,4 V)과 에너지 밀도가 높기 때문에 compact화가 가능하다[1].