• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.295-300
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• 2007

A new characterization method using a porous plug model was proposed to determine the degree of sulfonation (DS) of ionomer binder with respect to the membrane used in membrane-electrode assemblies (MEAs) and to analyze the fraction of proton pathways through ionomer-catalyst combined electrodes in MEAs for polymer electrolyte fuel cells (PEFCs). Sulfonated poly(ether ether ketone) was prepared to use a polymeric electrolyte and laboratory-made SPEEK solution (5wt.%, DMAc based) was added to catalyst slurry to form catalyst layers. In case of the SPEEK-based MEAs in this study, DS of ionomer binder for catalyst layers should be the same or higher than that of the SPEEK membrane used in the MEAs. The porous plug model suggested that most of protons were via the ionomer binder (${\sim}92.5%$) bridging the catalyst surface to the polymeric electrolyte, compared with the pathways through the alternative between the interstitial water on the surface of ionomer binder or catalyst and the ionomer binder (${\sim}7.3%$) and through only the interstitial water on the surface of ionomer or catalyst (${\sim}0.2%$) in the electrode of the MEA comprising of the sulfonated poly(ether ether ketone) membrane and the 5wt.% SPEEK ionomer binder. As a result, it was believed that the majority of proton at both electrodeds moves through ionomer binder until reaching to electrolyte membrane. The porous plug model of the electrodes of MEAs reemphasized the importance of well-optimized structure of ionomer binder and catalyst for fuel cells.

• Current Photovoltaic Research
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• v.2 no.1
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• pp.18-27
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• 2014

Dye-sensitized solar cells (DSSCs), developed two decades ago, are considered to be an attractive technology among various photovoltaic devices because of their low cost, accessible dye chemistry, ease of fabrication, high power conversion efficiency, and environmentally friendly nature. A typical DSSCs consists of a dye-coated $TiO_2$ photoanode, a redox electrolyte, and a platinum (Pt)-coated fluorine-doped tin oxide (FTO) counter electrode. Among them, redox electrolytes have proven to be extremely important in improving the performance of DSSCs. Due to many drawbacks of iodide electrolytes, many research groups have paid more attention to seeking other alternative electrolyte systems. With regard to this, one-electron outer sphere redox shuttles based on cobalt complexes have shown promising results: In 2014, porphyrin dye (SM315) with the cobalt (II/III) redox couple exhibited a power conversion efficiency of 13% in DSSCs. In this review, we will provide an overview and perspectives of cobalt redox electrolytes in DSSCs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.331-337
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• 2017

Thermal batteries, reserve power source, is activated by melting of molten salt at the temperature range of $350{\sim}550^{\circ}C$. To immobile the molten state electrolyte when the thermal battery is activated, the binder must be added in electrolyte. Usually, molten salts include 30~40 wt% of MgO binder to ensure electrical insulation as well as safety. However, the conventional MgO binder tends to increase ionic conductive resistance and thus the inclusion of the binder increases the total impedance of the battery. This paper mainly focused on the study of yttria stabilized zirconia (YSZ) as an alternative binder for molten salt. The chemical stability between the molten salt and YSZ is measured by XRD and DSC. And the sufficient path for ionic conduction on molten salt could be confirmed by the enhanced wetting behavior and the enlarged pore size of YSZ. The electrochemical properties were analyzed using single cell tests so that it showed the outstanding performance than that using MgO binder.

• Membrane Journal
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• v.20 no.3
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• pp.173-184
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• 2010

Microbial fuel cell (MFC) is a promising renewable energy source that can generate electrical energy from organic wastes using microbe. This technology has been regarded as a future green alternative energy in that MFC makes use of organic-rich wastewater and also reduces waste sludges as well as produces electricity. To be practically realized, however, achieving higher power density than now is demanded, which may be possible by eliminating various negative factors to act as resistances in MFC operations. For instance, highly activated microbes, highly conductive electrode materials, and fast electron transfer between microbes and electrodes can lead to MFC with high power density. In particular, polymer electrolyte membranes are also a key component for improved MFC performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.1-9
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• 2023

According to the recent global warming, it is necessary to use energy efficiently together with eco-friendly energy. The development of alternative technologies is requisite for managing the current energy and climate crises. In this regard, "smart windows," which can control solar radiation, can be used to mitigate energy demands. Electrochromic devices (ECDs) effectively control the amount of solar energy reaching commercial and other living areas and maintain climate conditions via color modulation in response to small external stimuli, such as temperature and light irradiation. However, the performance and the stability of ECDs depend on the state of the electrolyte and sealing of the device. To resolve the aforementioned issues, an ECD was manufactured by using a poly (methyl methacrylate) (PMMA)-based gel polymer electrolyte (GPE), and a laminating method was used to adequately seal the ECD. The concentrations of PMMA, acetonitrile (ACN), and ferrocene (Fc) were controlled to optimize the composition of the GPE to achieve an enhanced electrochromic performance. The fabricated GPE-based ECD afforded high optical contrast (~81.92%), with high electrochromic stability up to 10,000 cycles. Moreover, the lamination method employing the GPE could be used to fabricate large-area ECDs.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.334-342
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• 2024

The need for efficient and sustainable energy storage solutions has emerged due to a rapidly increasing energy demand and growing concerns about environmental issues. Among various energy storage methods, lithium secondary batteries are widely used in a variety of electronic devices such as smartphones, laptops, electric vehicles, and large-scale power storage systems due to their high energy density, long lifespan, and cost competitiveness. Recently, all-solid-state batteries (ASSBs) have attracted great attention because they can reduce the risk of fire associated with liquid electrolytes. Additionally, using high-capacity alternative anodes and cathodes in ASSBs can enhance energy density. However, ASSBs that use solid electrolytes experience a degradation in their electrochemical performances due to resistance at solid-solid interfaces. These interfaces can also result in poor physical contact and the presence of products formed from chemical and electrochemical reactions. Solving this interface problem is a critical issue for the commercialization of ASSBs. This review summarizes interfacial reactions between the cathode and solid electrolyte, along with research aimed at improving these interactions. Future development directions in this field are also discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.127-130
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• 2003

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusions and improves mechanical and corrosion resistance of stainless steel. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of a metal object. An electrolyte of phosphoric, sulfuric and distilled water has been used in this study. In the low current density region, there can be found plateau region and material removal process and leveling process occur successively. In this study, an electrochemical polishing process using pulse current is adopted as a new electrochemical polishing process. In electrochemical machining processes, it has been found that pulse electrochemical processes provide an attractive alternative to the electrochemical processes using continuous current. Hence, this study will discuss the electrochemical polishing processes in low current density region and pulse electrochemical polishing.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.388-393
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• 2003

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusions and improves mechanical and corrosion resistance of stainless steel. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of a metal object. An electrolyte of phosphoric acid 50% in vol., sulfuric acid 20% in vol. and distilled water 30% in vol. has been used in this study. In the low current density region, there can be found plateau region and material removal process and leveling process occur successively. In this study, an electrochemical polishing process using pulse current is adopted as a new electrochemical polishing process. In electrochemical machining processes, it has been found that pulse electrochemical processes provide an attractive alternative to the electrochemical processes using continuous current. Hence, this study will discuss the electrochemical polishing processes in low current density region and pulse electrochemical polishing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.467-472
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• 2015

Thermal batteries are primary power sources for military applications requiring high reliability, robustness and long storage life. Conventional electrodes for thermal batteries are prepared by compacting powder mixtures into pellets. Separator is composed of halide mixture, such as LiCl-KCl eutectic salt, blended with MgO to immobilize the molten salt. In order to increase the power density and energy density, the resistance of electrolyte should be reduced because the resistance of electrolyte is predominant in thermal batteries. In this study, wetting behaviors and impregnation weight of molten salts as well as the micro structures of ceramic felt were investigated to be applicable to thin electrolyte. Discharge performances of single cell with the ceramic separator impregnated by molten salt were evaluated also. Zirconia felt with high porosity and large pore outperformed alumina felt in wetting characteristics and molten salt impregnation as well as discharge performances. Based on the results of this study, ceramic felt separator impregnated with molten salt have revealed as an alternative of conventional thick MgO based separator with no conspicuous sign of thermal runaway by short circuit.

• Journal of the Korean Electrochemical Society
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• v.21 no.3
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• pp.55-60
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• 2018

The demand for LIBs with higher energy densities has increased continuously because the emergence of wider and more challenging applications including HEV and EV has became imperative. However, in the case of anode material, graphite is insufficient to meet this need. To meet such demand, several type of negative electrode materials like silicon, tin, SiO, and transition metal oxide have been investigated for the advanced lithium secondary batteries. Recently, lithium vanadium oxide, which has a layered structure, is assumed as one of the promising anode material as alternative of graphite. This material shows a high volumetric capacity, which is 1.5 times higher than that of graphite. However, relative low electrical conductivity and particle fracture, which results in the electrolyte decomposition and loss of electric contact between electrode, induce rapid capacity decay. In this report, we investigated the effect of electrolyte additive on the electrochemical characteristics of lithium vanadium oxide.