• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.152-156
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• 2000

The effect of cupric ion concentration on the throwing power has been studied in the electrodeposition of Cu on the porous reticular electrodes with the electrolytes of $CuSO_4\;and\;H_2SO_4$. Sulfuric acid electrolytes with lower concentration of $CuSO_4$ improved throwing power in electrodeposition of copper not only due to higher cathodic polarizability but also due to higher conductivity of the electrolytes. The increase in conductivity of the electrolytes at low concentration of $CuSO_4$ could be also illustrated by the decrease in viscosity of the electrolytes. It was found that both the throwing power and the limiting current density should be taken into account in the electrodeposition of Cu on the reticular electrodes. According to the experimental results, the electrolyte of 0.2M $CuSO_4$ and 0.5M $H_2SO_4$ was found to be the most appropriate condition at the current density of $10mA/cm^2$.

• Journal of the Korean Electrochemical Society
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• v.25 no.3
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• pp.95-104
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• 2022

The development of non-flammable all-solid-state batteries (ASSLBs) has become a hot topic due to the known drawbacks of commercial lithium-ion batteries. As the possibility of applying sulfide solid electrolytes (SSEs) for electric vehicle batteries increases, efforts for the low-cost mass-production are actively underway. Until now, most studies have used high-energy mechanical milling, which is easy to control composition and impurities and can reduce the process time. Through this, various SSEs that exceed the Li⁺ conductivity of liquid electrolytes have been reported, and expectations for the realization of ASSLBs are growing. However, the high-energy mechanical milling method has disadvantages in obtaining the same physical properties when mass-produced, and in controlling the particle size or shape, so that physical properties deteriorate during the full process. On the other hand, wet chemical synthesis technology, which has advantages in mass production and low price, is still in the initial exploration stage. In this technology, SSEs are mainly manufactured through producing a particle-type, solution-type, or mixed-type precursor, but a clear understanding of the reaction mechanism hasn't been made yet. In this review, wet chemical synthesis technologies for SSEs are summarized regarding the reaction mechanism between the raw materials in the solvent.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.14-20
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• 2016

Vanadium redox flow battery (VRFB) is an energy conversion device in which charging and discharging are alternatively carried out by oxidation and reduction reactions of vanadium ions with different oxidation states. VRFB consists of electrolyte, electrode, ion-exchange membrane, etc. The role of ion-exchange membranes in VRFB separates anolyte and catholyte and provides a high conductivity to hydrogen ions. Recently much attention has been devoted to develop ideal ion-exchange membranes for VRFB. A number of developed ion-exchange membranes should be evaluated to find out ideal ion-exchange membranes for VRFB. Long-term durability test is a crucial characterization of ion-exchange membranes for commercialization, but is very time-consuming. In this study, the life time prediction protocol of ion-exchange membranes in VRFB cell tests was developed through short-term single cell performance evaluation (real total operation time, 87.5 hrs) at three different current densities. We confirmed a decrease in test time up to 96.2% of real durability tests (expected total operation time, 2,296 hrs) and 5~6% of relative error discrepancy between the predicted and the real life time in a unit cell.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.100-105
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• 2021

Recently, all-solid-state batteries have attracted much attention to improve safety of rechargeable lithium batteries, but the solid-state batteries of conductive ceramics or solid polymer electrolytes show poor electrochemical properties because of several problems such as high interfacial resistance and undesired reactions. To solve the problems of the reported all-solid-state batteries, a hybrid solid electrolyte is suggested, in this study, NASICON-type nanoparticle Li_1.5Al_0.5Ti_1.5P₃O₁₂ (LATP) conductive ceramic, PVdF-HFP, and a carbonate-based liquid electrolyte were composited to prepare a quasi-solid electrolyte. The hybrid solid electrolyte has a high voltage stability of 5.6 V and shows an suppress effect of lithium dendrite growth in the stripping-plating test. The LiNi_0.83Co_0.11Mn_0.06O₂ (NCM811)-based battery with the hybrid solid electrolyte exhibits a high discharge capacity of 241.5 mAh/g at a high charge-cut-off voltage of 4.8V and stable electrochemical reaction. The NCM811-based battery also shows 139.4 mAh/g discharge capacity without short circuit or explosion at 90℃. Therefore, the LATP-based hybrid solid electrolyte can be an effective solution to improve the safety and electrochemical properties of rechargeable lithium batteries.

• Journal of the Korean Chemical Society
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• v.62 no.1
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• pp.24-29
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• 2018

Despite the great potential for the versatile applications in food industry and medical area, chitosan as a biocompatible cationic polysaccharide has suffered from the limited solubility under physiological condition. Herein, we demonstrated the electrostatic formation of chitosan-based polyplex particles, counterbalanced by polyacrylate as an anionic polyelectrolyte. The resulting polyplex exhibited pH- and composition-dependent changes in their surface charges as measured by zeta potential, which can be employed to provide the interparticle repulsive forces for enhanced colloidal stability in homogeneous solution. Subsequently, amide coupling between the acrylates and glucosamine residues of chitosan inside the polyplex further generated the hydrogel particles, which showed the temperature-sensitive swelling property. This aspect can be attributed to the partial formation of acryl amide residues, which have been generally known to possess the lower critical solution temperature (LCST).

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.65-65
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• 2009

철강 재료의 GMA 용접 시, 보호가스로 $CO_2$ 가스를 사용하면 가격이 저렴하고 용입이 깊다는 장점이 있어 국내에서 광범위하게 사용되어 왔다. 그러나 일반적으로 활성가스인 $CO_2$를 사용한 GMA용접은 아크가 불안정하고 스패터가 많이 발생한다는 단점이 있어 아크 안정성 개선의 필요성이 부각되었다. 거기다 용접 자동화 및 용접 품질의 고급화 추세로 아크 안정성이 $CO_2$용접에서 점점 중요해지면서, 아크 안정화 및 스패터 저감을 위한 연구가 활발히 진행되어 왔다. 본 연구에서는 GMA 용접 재료인 solid wire의 표면에 이온화 에너지가 낮은 금속인 인듐(In)을 전해 도금하여 중전류의 $CO_2$ 용접에 적용하였다. 고속 촬영과 아크 모니터링 분석을 통하여 금속 이행 모드 및 아크 안정화에 미치는 영향에 관하여 연구하였다. 동일 전압, 전류 조건에서 도금 두께를 달리하여 용접을 실시, 도금 두께에 따른 아크 안정성의 경향을 분석하였다. 그 결과 도금 두께가 두꺼워짐에 따라 아크가 넓어지는 것을 확인하였으며, 이는 아크 내에 이온화도가 높은 인듐 이온이 다량 포함됨으로써 이온의 양이 증가하기 때문인 것으로 생각된다. 또한 도금 두께가 일정 이상이 되면, 이행 모드가 용적의 아래에서 아크가 발생하는 반발 이행 모드에서 용적의 윗부분에서 아크가 발생하는 입상 용적 이행 모드로 바뀌었으며, 이때 단락 수가 현저히 줄어들어 아크가 안정해졌다. 이에 따라 인듐 도금 와이어는 기존보다 낮은 전류 영역에서도 안정적인 아크와 금속 이행 모드를 가지게 됨을 확인하였다.

• Membrane Journal
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• v.13 no.3
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• pp.143-153
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• 2003

The effects of bipolar interface formed on the surface of cation-exchange membrane on water splitting phenomena were investigated. Results showed that the formation of immobilized bipolar interface resulted in significant water splitting during electrodialysis. In particular, the immobilized bipolar interface was easily created on the cation-exchange membrane surface in the electrodialytic systems where multivalent cations served as an electrolyte. Multivalent cations with low solubility product resulted in violent water splitting because they were easily precipitated on the membrane surface in hydroxide form. Therefore, the bipolar interface consisting of H- and OH-affinity groups were formed on the membrane-solution interface. Apparently, water splitting was largely activated with the help of strong electric fields generated between the metal hydroxide layer and fixed charge groups on the membrane surface. Likewise, the accumulation of large molecular counter ions on the membrane surface led to the formation of a fixed bipolar structure that could cause significant water splitting in the over-limiting current region. Therefore, the prevention of the immobilization of bipolar interface on the membrane surface is very essential in improving the process efficiency in a high-current operation.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.395-399
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• 2011

Material of the gasket for lithium ion battery requires the chemical resistance, the electrical insulting property, the compression set, the anti-contamination level and the low temperature resistance. We compounded ethylene propylene diene monomer (EPDM), which showed widely different solubility parameter index, with adjusting the amount of metal oxide as an activator. We did long-term test and compression set against an electrolyte with consideration for operating conditions in lithium-ion battery. In these tests, we checked the physical, chemical characteristics and the effect to lithium ion battery with different kinds of activators. In case of rubber with ZnO as an activator, through 1000 h depositing test in propylene carbonate which is one of representative solvents, we could get the satisfying characteristics and result. However, $Zn^{2+}$ had eluted in the ion elution test. So, ZnO should be limited in EPDM compound for the gasket material in lithium-ion battery.

• Polymer(Korea)
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• v.25 no.4
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• pp.602-607
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• 2001

Bis(2-methoxyethyl)itaconate (bis(ME)I) was prepared for a new gel electrolyte containing double comb-like itaconate unit by esterification reaction of 2-methoxyethanol with itaconic acid. The copolymers were composed of AN/bis(ME)I = 9/1 ~ 1/1. The optimum mechanical properties and conductivity were obtained from the composition of AN/bis(ME)I = 5/1 and 6/1(25 ~ 35 wt%), LiClO4$_4$(15 wt%) and plasticizer (EC/PC = 1/1) (40 ~ 50 wt%). They showed a tough film and maintained a mechanical stability as a free standing film. The plasticized polymer gel electrolytes obtained from them showed ion conductivity of 8.12 ${\times}$ 10$_{-4}$ ~ 1.87 ${\times}$ 10$_{-3}$ S/cm. The maximum conductivity value obtained from our study was one order of magnitude higher than that of other PEO-based polymer electrolyte at ambient temperature.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.19-26
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• 2012

SEI (solid electrolyte interphase) layers are generated on a graphite negative electrode from three different electrolytes and low-temperature ($-30^{\circ}C$) charge/discharge performance of the graphite electrode is examined. The electrolytes are prepared by adding 2 wt% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) into a standard electrolyte solution. The charge-discharge capacity of graphite electrode shows the following decreasing order; FEC-added one>standard>VC-added one. The polarization during a constant-current charging shows the reverse order. These observations illustrate that the SEI film resistance and charge transfer resistance differ according to the used additives. This feature has been confirmed by analyzing the chemical composition and thickness of three SEI layers. The SEI layer generated from the standard electrolyte is composed of polymeric carbon-oxygen species and the decomposition products ($Li_xPF_yO_z$) of lithium salt. The VC-derived surface film shows the largest resistance value even if the salt decomposition is not severe due to the presence of dense film comprising C-O species. The FEC-derived SEI layer shows the lowest resistance value as the C-O species are less populated and salt decomposition is not serious. In short, the FEC-added electrolyte generates the SEI layer of the smallest resistance to give the best low-temperature performance for the graphite negative electrode.