• Membrane Journal
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• v.27 no.5
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• pp.406-414
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• 2017

In this study, we have developed pore-filled ion-exchange membranes (PFIEMs) filled with ionomer in a thin polyethylene porous film (thickness = $25{\mu}m$) and investigated the charge-discharge characteristics of the all vanadium redox flow battery (VRFB) employing them. Especially, the degree of crosslinking and free volume of the PFIEMs were appropriately controlled to produce ion-exchange membranes exhibiting both the low membrane resistance and low vanadium permeability by mixing crosslinking agents having different molecular size. As a result, the prepared PFIEMs exhibited excellent electrochemical properties which are comparable to those of the commercial membranes. Also, it was confirmed through the experiments of vanadium ion permeability and VRFB performance evaluation that the PFIEMs showed low vanadium ion permeability and high charge-discharge efficiency in comparison with the commercial membrane despite their thin film thickness.

• Journal of the Korean institute of surface engineering
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• v.52 no.3
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• pp.150-155
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• 2019

The carbon electrode was modified through manganese-catalyzed hydrogenation method for high energy density vanadium redox flow battery (VRFB). During the catalytic hydrogenation, the manganese oxide deposited at the surface of the carbon electrode stimulated the conversion reaction from carbon to methane gas. This reaction causes the penetration of the manganese and excavates a number of cavities at electrode surface, which increases the electrochemical activity by inducing additional electrochemically active site. The formation of the porous surface was confirmed by the scanning electron microscopy (SEM) images. Finally, the electrochemical performance test of the electrode with the porous surface showed lower polarization and high reversibility in the cathodic reaction compared to the conventional electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.372-377
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• 2016

The carbon felt used as the electrode of vanadium redox flow battery (VRFB) requires imprived electrochemical activity for better battery performance and efficiencies. Many efforts have been tried to improve electrochemical activity of the carbon felt as electrodes. In this study the alkali solution, KOH, is applied on surface treatment of the carbon felt electrode. The carbon felts were treated with KOH under room temperature and $80^{\circ}C$. The isopropyl alcohol was applied to improve wettability of the carbon felt during KOH treatment. The KOH treated carbon felt was analyzed by using the X-ray photoelectron spectroscopy (XPS). The XPS analysis of carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after KOH treatment. Also, cyclic voltametry tests showed electrochemical characteristics enhancement of the carbon felt.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.42-47
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• 2000

The amorphous vanadium oxide thin films for thin-film rechargeable lithium batteries were fabricated by r.f. reactive sputtering at room temperature. As the experimental parameter, oxygen partial pressure was varied during sputtering. At high oxygen partial pressures(>30%), the as-deposited films, constant current charge/discharge characteristics were carried out in 1M $LiPF_6$, EC:DMC+1:1 liquid electrolyte using lithium metal as anode. The specific capacity of amorphous $V_2O_5$ after 200cycles of operation at room temperature was higher compared to crystalline $V_2O_5$. The amorphous vanadium oxide thin film and crystalline film showed about 60$\mu$Ah/$\textrm{cm}^2\mu\textrm{m}$ and about 38$\mu$Ah/$\textrm{cm}^2\mu\textrm{m}$, respectively. These results suggest that the battery capacity of the thin film vanadium oxide cathode strongly depends on the crystallinity.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1651-1655
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• 2013

Anion exchange membranes for a vanadium redox flow battery (VRB) were prepared by pore-filling on a PE substrate with the copolymerization of vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA). The ion exchange capacity, water uptake and weight gain ratio were increased with a similar tendency up to 65% of GMA content, indicating that the monomer improved the pore-filling degree and membrane properties. The vanadium ion permeability and open-circuit voltage were also investigated. The permeability of the VG65 membrane was only $1.23{\times}10^{-7}\;cm^2\;min^{-1}$ compared to $17.9{\times}10^{-7}\;cm^2\;min^{-1}$ for Nafion 117 and $1.8{\times}10^{-7}\;cm^2\;min^{-1}$ for AMV. Consequently, a VRB single cell using the prepared membrane showed higher energy efficiency (over 80%) of up to 100 cycles compared to the commercial membranes, Nafion 117 (ca. 58%) and AMV (ca. 70%).

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.256-262
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• 2021

A carbon felt electrode was prepared using ozone and ammonia sequential treatment and applied as an electrode for a vanadium redox flow battery (VRFB). The physical and electrochemical analyses demonstrate that the oxygen groups facilitate nitrogen doping in the carbon felt. Carbon felt (J5O3+NH3), which was subjected to ammonia heat treatment after ozone treatment, showed higher oxygen and nitrogen contents than carbon felt (J5NH3+O3), which was subjected to ammonia heat treatment first and then ozone treatment. From the charging/discharging of VRFB, the J5O3+NH3 carbon felt electrode showed 14.4 Ah/L discharge capacity at a current density of 150 mA /cm², which was 15% and 33% higher than that of J5NH3+O3 and non-activated carbon felt (J5), respectively. These results show that ozone and ammonia sequential treatment is an effective carbon felt activation method to increase the performance of the vanadium redox flow battery.

• 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.

• 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).

• Transactions of the Korean hydrogen and new energy society
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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.