• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.395-398
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• 1998

Lithium insertion has been studied in a number of vanadium oxides with special regard to their application as the active materials in rechargeable lithium cells. Very high stoichiometric energy densities for lithium insertion are found for several of these materials. Some vanadium oxides, e.g. V$_2$ $O_{5}$ and V$_{6}$ $O_{13}$, are now being used in commercially developed rechargeable Li batteries. Another material which is receiving remarkable attention for this kind of cells is LiV$_3$ $O_{8}$. In variety of ternary lithium-vanadium oxides, the lithium content can be varied between certain limits without major changes in the vanadium oxygen lattice. In our worts, the oxides which do net form these thermodynamically stable bronzes can still accommodate large amounts of lithium at ambient temperature, forming kinetically stable insertion compounds. These compounds owe their existence to the whereas lithium is easily introduced into these open structures. The oxides investigated are rather poor electronic conductors; the conductivity decrease with increase in the lithium content. Improvements in the electrode fabrication technique are needed to alleviate this Problem.oblem.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.131-138
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• 2023

The carbon felt is usually hired as electrodes for vanadium redox flow battery (VRFB). In the study, surface modification of carbon felt under CO₂ atmosphere with variables of operating various temperature ranges between 700℃ and 900℃. The qualitative and quantitative analysis were carried out such as scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to observe degree of surface modification. Result of XPS analysis confirmed increase of carbon and oxidation functional group on the surface with increase of temperature. SEM image was discovered similar phenomena. Electrochemical characteristics such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the improved electrode performance with increase of temperature. However, the electrochemical performance under treatments temperature of 900℃ was less than that of under treatment temperature of 850℃ due to weight loss at the treatment temperature of 900℃. From the CV and EIS results, the best electrochemical characteristics was at the temperature of 850℃. That of at the temperature of 900℃ was decreased due to weight loss. The energy efficiencies (EE) obtained from full cell test were 69.37, 80.76, 82.45, and 75.47%, at the temperature of 700, 800, 850, and 900℃, respectively.

• Composites Research
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• v.37 no.3
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• pp.190-196
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• 2024

The bipolar plate is a crucial element of the vanadium redox flow battery (VRFB) as it serves as both the electrical conduit and the structural support for the cell within the VRFB stack. Although, the graphite material is primarily used for the bipolar plate due to its excellent electrical conductivity, a significant limitation of performance of the VRFB is present due to high interfacial contact resistance (ICR) arises between the electrode and bipolar plate in the cell stack. This study aims to develop an integrated electrode-bipolar plate assembly that will address the limitations of the ICR. The integrated assembly was constructed using a single carbon felt with thermoplastic and thermoset polymers utilizing hot press method. Experimental results verify that the bipolar plate assembly exhibits reduced area specific resistance (ASR) due to the continuous electrical path. Additionally, from the charge/discharge cell test results, the integrated assembly shows improved cell performance. Therefore, the developed integrated electrode-bipolar plate assembly can serve as a substitute for the conventional bipolar plate and electrode assembly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.12
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• pp.777-784
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• 2016

All-vanadium redox flow batteries (VRFBs) are used as energy storage systems for multiple intermittent power sources. The performance of the VRFBs depends on the materials and operating conditions. Hence, performance characterization is of great importance in the development of the VRFBs. This paper proposes a method for determining the maximum current density based on stoichiometric ratios. A laboratory-scaled VRFB with a projected electrode area of $25cm^2$ is electrically charged when the state of the charge has begun from 0.6. The operating conditions, such as current density and volumetric flow rate are important in the test, and the maximum current density is influenced by the mass transfer coefficient. The results show that increasing the electrolyte flow rate from 5 mL/min to 60 mL/min enhances the maximum current density up to $520mA/cm^2$.

• Membrane Journal
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• v.29 no.3
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• pp.155-163
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• 2019

The anion exchange membrane using the blending polymer of poly(ether sulfone) and poly(phenylene sulfide sulfone) was prepared. It was confirmed by EDXS and FT-IR analysis that the prepared anion exchange membrane had the -N- as an anion exchange group. The ionic conductivity in 1 mol/L $H_2SO_4$ aqueous solution was measured. The ionic conductivity of the prepared anion exchange membrane was 0.015~0.083 S/cm, and had a high value compared with AFN and APS as a commercial anion exchange membrane. Permeabilities of the vanadium ions through the prepared anion exchange membrane were tested to evaluate the possibility as a separator in vanadium redox flow battery. Vanadium ion permeation rate in the prepared anion exchange membrane had a low value compared with Nafion 117 as a commercial cation exchange and AFN as a commercial anion exchange membrane.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.408-412
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• 2019

In this study, nitrogen doped carbon felt was prepared by pyrolysis of urea at high temperature and applied as an electrode for vanadium redox flow cell. Urea is easier to handle than ammonia and forms $NH_2$ radicals at higher temperatures, creating a nitrogen functional group on the carbon surface and acting as an active site in the vanadium redox reaction. Therefore, the discharge capacity of activated carbon felt electrodes using urea was 14.9 Ah/L at a current density of $150mA/cm^2$, which is 23% and 187% higher than OGF and GF, respectively. These results show the possibility that activated carbon felt electrode using urea can be used as electrode material for redox flow battery.

• Analytical Science and Technology
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• v.28 no.5
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• pp.341-346
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• 2015

In order to understand the counter anionic effects in a non-aqueous vanadium redox flow battery (VRFB), we synthesized four types of electrolyte salts (1-ethyltriethamine tertafluoroborate, [E-TEDA]⁺[BF₄]⁻, 1-ethyltriethamine hexafluorophosphate, [E-TEDA]⁺[PF₆]⁻, 1-butyltriethylamine tertafluoroborate, [B-TEDA]⁺[BF₄]⁻, and 1-buthyltriethamine hexafluorophosphate [B-TEDA]⁺[PF₆]⁻) by counter anion exchange reaction after the SN₂ reaction. We confirmed the successful synthesis of the electrolyte salts [E-TEDA]⁺[Br]⁻ and [B-TEDA]⁺[Br]⁻ via ¹H-NMR spectroscopy and GC-mass analysis before the counter anion exchange reaction. The electric potential of the vanadium acetylacetonate, V(acac)₃, as an energy storage chemical was shown to be 2.2 V in the acetonitrile solvent with each of the [E-TEDA]⁺[BF₄]⁻, [E-TEDA]⁺[PF₆]⁻, [B-TEDA]⁺[BF₄]⁻, and [B-TEDA]⁺[PF₆]⁻ electrolyte salts. In a non-aqueous VRFB with a commercial Neosepta AFN membrane, the maximum voltages reached 1.0 V and 1.5 V under a fixed current value of 0.1 mA in acetonitrile with the [E-TEDA]⁺[BF₄]⁻ and [E-TEDA]⁺[PF₆]⁻ electrolyte salts, respectively. The maximum voltage was 0.8 V and 1.1 V under a fixed current value of 0.1 mA in acetonitrile with the [B-TEDA]⁺[BF₄]⁻ and [B-TEDA]⁺[PF₆]⁻ electrolyte salts, respectively. From these results, we concluded that in the non-aqueous VRFB more of the [PF₆]⁻ counter anion than the [BF₄]⁻ counter anion was transported onto the commercial Neosepta AFN anion exchange membrane.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.781-797
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• 2023

Recently, there has been a rapid response from mineral-demanding countries for securing critical minerals in a high tech industries. Graphite, while overwhelmingly dominated by China in production, is changing in global supply due to the exponential growth in EV battery sector, with active exploration in East Africa. Rare earth elements are essential raw materials widely used in advanced industries. Globally, there are ongoing developments in the production of REEs from three main deposit types: carbonatite, laterite, and ion-adsorption clay types. While China's production has decreased somewhat, it still maintains overwhelming dominance in this sector. Recent changes over the past few years include the rapid emergence of Myanmar and increased production in Vietnam. Nickel has been used in various chemical and metal industries for a long time, but recently, its significance in the market has been increasing, particularly in the battery sector. Worldwide, nickel deposits can be broadly classified into two types: laterite-type, which are derived from ultramafic rocks, and ultramafic hosted sulfide-type. It is predicted that the development of sulfide-type, primarily in Australia, will continue to grow, while the development of laterite-type is expected to be promoted in Indonesia. This is largely driven by the growing demand for nickel in response to the demand for lithium-ion batteries. The global lithium ores are produced in three main types: brine lake (78%), rock/mineral (19%), and clay types (3%). Rock/mineral type has a slightly higher grade compared to brine lake type, but they are less abundant. Chile, Argentina, and the United States primarily produce lithium from brine lake deposits, while Australia and China extract lithium from both brine lake and rock/mineral sources. Canada, on the other hand, exclusively produces lithium from rock/mineral type. Vanadium has traditionally been used in steel alloys, accounting for approximately 90% of its usage. However, there is a growing trend in the use for vanadium redox flow batteries, particularly for large-scale energy storage applications. The global sources of vanadium can be broadly categorized into two main types: vanadium contained in iron ore (81%) produced from mines and vanadium recovered from by-products (secondary sources, 18%). The primary source, accounting for 81%, is vanadium-iron ores, with 70% derived from vanadium slag in the steel making process and 30% from ore mined in primary sources. Intermediate vanadium oxides are manufactured from these sources. Vanadium deposits are classified into four types: vanadiferous titanomagnetite (VTM), sandstone-hosted, shale-hosted, and vanadate types. Currently, only the VTM-type ore is being produced.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.219-223
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• 2000

All-solid state lithium rechargeable thin film batteries were fabricated with the configuration of$Cu_{0.5}V_2O_5/Lipon/Li$ using sequential thin film techniques. Copper vanadium oxide thin films and Lipon thin films were prepared by DC reactive dual source magnetron sputtering and RF magnetron sputtering, respectively. According to XRD analysis, we found out that copper vanadium oxide thin films were amorphous. The electrochemical behaviour of them was examined in half cell system using EC : DMC(1:1 in IM $LiPF_5$) liquid electrolyte. The ionic conductivity of Lipon thin film was $1.02\times10^{-6}S/cm$ at $25^{\circ}C$ and $Cu_{0.5}V_2O_5/Lipon/Li$ cell showed that the discharge capacity was about $50{\mu}Ah/cm^2{\mu}m$ beyond 500cyc1es.

• 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.