• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.1-13
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• 2024

This paper presents applications of lithium-sulfur (Li-S) energy storage batteries, while showing merits and demerits of several techniques to mitigate their electrochemical challenges. Unmanned aerial vehicles, electric cars, and grid-scale energy storage systems represent main applications of Li-S batteries due to their low cost, high specific capacity, and light weight. However, polysulfide shuttle effects, low conductivities, and low coulombic efficiencies signify key challenges of Li-S batteries, causing high volumetric changes, dendritic growths, and limited cycling performances. Solid-state electrolytes, interfacial interlayers, and electrocatalysts denote promising methods to mitigate such challenges. Moreover, nanomaterials have capability to improve kinetic reactions of Li-S batteries based on several properties of nanoparticles to immobilize sulfur in cathodes, stabilizing lithium in anodes while controlling volumetric growths. Li-S energy storage technologies are able to satisfy requirements of future markets for advanced rechargeable batteries with high-power densities and low costs, considering environmentally friendly systems based on renewable energy sources.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.423-428
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• 2010

To reduce polarization of electrochemical capacitor based on carbon nanotube, titanium oxide nanoparticles were deposited by ultrasound. The pore distribution of $TiO_2$/CNT nanoparticle exhibited surface area of $341\;m^2g^{-1}$ when $TiO_2$ content was 4 wt %, which was better than that of pristine CNT with surface area of $188\;m^2g^{-1}$. The analyses indicated that titanium oxide (particle diameter < 20 nm) was deposited on the CNT surface. The electrochemical performance was evaluated by using cyclic voltammetry (CV), impedance measurement, and constant-current charge/discharge cycling techniques. The $TiO_2$/CNT composite electrode showed relatively better electrochemical behaviors than CNT electrode by increasing the specific capacitance from $22\;Fg^{-1}$ to $37\;Fg^{-1}$ in 1 M $H_2SO_4$ solution. A symmetric cell assembled with the composite electrodes showed the specific capacitance value of $11\;Fg^{-1}$ at a current loading of $0.5\;mAcm^{-2}$ during initial cycling.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.1-13
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• 2020

As research on secondary batteries becomes important, interest in analytical methods to examine the condition of secondary batteries is also increasing. Among these methods, the electrochemical impedance spectroscopy (EIS) method is one of the most attractive diagnostic techniques due to its convenience, quickness, accuracy, and low cost. However, since the obtained spectra are complicated signals representing several impedance elements, it is necessary to understand the whole electrochemical environment for a meaningful analysis. Based on the understanding of the whole system, the circuit elements constituting the cell can be obtained through construction of a physically sound circuit model. Therefore, this mini-review will explain how to construct a physically sound circuit model according to the characteristics of the battery cell system and then introduce the relationship between the obtained resistances of the bulk (R_b), charge transfer reaction (R_ct), interface layer (R_SEI), diffusion process (W) and battery characteristics, such as the state of charge (SOC), temperature, and state of health (SOH).

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.277-285
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• 2016

There is a growing demand for simple, cost-effective, and accurate analytical tools to determine the concentrations of biological and environmental compounds. In this study, a stable electroactive thin film of cobalt hexacyanoferrate (Cohcf) was prepared as an in situ chemical precipitant using electrostatic adsorption of $Co^{2+}$ on a silicate sol-gel matrix (SSG)-modified indium tin oxide electrode pre-adsorbed with $[Fe(CN)_6]^{3-}$ ions. The modified electrode was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. Electrocatalytic oxidation of hydrazine on the modified electrode was studied. An electrochemical sensor for hydrazine was constructed on the SSG-Cohcf-modified electrode. The oxidation peak currents showed a linear relationship with the hydrazine concentration. This study provides insight into the in situ growth and stability behavior of Cohcf nanostructures and has implications for the design and development of advanced electrode materials for fuel cells and sensor applications.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.43-52
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• 2019

As the application area of lithium secondary batteries becomes wider, performance characterization becomes difficult as well as diverse. To address this issue, battery manufacturers have to evaluate many batteries for a longer period, recruit many researchers and continuously introduce expensive equipment. Simulation techniques based on battery modeling are being introduced to solve such difficulties. Various lithium secondary battery modeling techniques have been reported so far and optimal techniques have been selected and utilized according to their purpose. In this review, the electrochemical modeling based on the Newman model is described in detail. Particularly, we will explain the physical meaning of each equation included in the model; the Butler-Volmer equation, which represents the rate of electrode reaction, the material and charge balance equations for each phase (solid and liquid), and the energy balance. Moreover, simple modeling processes and results based on COMSOL Multiphysics 5.3a will be provided and discussed.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.272-278
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• 2013

Extract of ginger has been evaluated as a green inhibitor for the corrosion of steel in sulfide polluted NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Potentiodynamic polarization measurements showed that this extract acts as a mixed type inhibitor but mainly inhibits the cathodic reaction. The inhibition efficiency was found to increase with inhibitor concentration reaching to approximately 83.9% using 250 ppm of ginger. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. The adsorption process of the studied extract on steel surface obeys Temkin adsorption isotherm. The results obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in measurement of corrosion rate. Ginger extract has no effect on Escherichia Coli and can be applied safely on waste water treatment plants.

• Corrosion Science and Technology
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• v.18 no.5
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• pp.155-167
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• 2019

In this study, two novel Schiff base compounds including (3-(4-Chlorophenyl isoxazole-5-yl) methanol and (3-(2,4 dichlorophenol isoxazole-5-yl) methanol as corrosion inhibitors for mild steel in 1 M hydrochloric acid solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) computations. The results showed that the corrosion inhibition efficiency (IE) is remarkably enhanced with the growing concentration of the Schiff base inhibitors. The results from Tafel polarization and EIS methods showed that IE decreases with gradual increments of temperature. This process can be attributed to the displacement of the adsorption/desorption balance and hence to the diminution of the level of a surface coating. Also, the adsorption of two inhibitors over mild steel followed the Langmuir adsorption isotherm. Too, the results of the scanning electron microscope (SEM) images showed that the Schiff base inhibitors form an excellent protective film over mild steel and verified the results by electrochemical techniques. Additionally, the results from the experimental and those from DFT computations are in excellent accordance.

• 한국전기화학회:학술대회논문집
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• 1999.11a
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• pp.83-91
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• 1999

Technical advances in manufacturing techniques and applied technologies have been made for bi cell manufacture, and are currently being implemented in the areas of discrete electrode / bi cell assembly, and electrode / separator lamination. Not only have improvements been noted in the reliability of the mechanical assembly and the increase in yields and decrease in costs, battery electrical performance has also been enhanced thru these assembly techniques. Evidence has been shown that the lamination techniques can influence porosity and electrolyte dispersion, and therefore electrical performance and long term reliability of the cells.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.106-111
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• 2018

In this work, we propose techniques for estimating the SOC of Li-air battery. First, we describe and explain the operation principle of the Li-air battery. Energy density of the Li-air battery was compared with that of the Li-ion battery. The capacity and impedance value of the fully discharged voltage is analyzed, and the OCV value for SOC estimation is measured through the electrochemical characterization of the Li-air battery. Estimation value is obtained by SOC modeling through extended Kaman filter and is compared with the measurement value from the Coulomb counting method. Moreover, the performance of SOC estimation circuit is evaluated.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.300-309
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• 2010

The influences of sensitization on localized corrosion resistance of 304 stainless steel, were investigated, using micro-dropletcell techniques. Micro-droplet cell allows one to align the micro-electrode to the desired spot of the working electrode and measure directly local current with the potentiodynamic polarization, linear polarization and a.c. impedance. Micro-electrochemical tests were carried out inside of the grain and on grain boundaries separately. It was found that sensitization decreased the pitting potential, increasing corrosion current density around grain boundaries. Galvanic current density was also measured between grain and grain boundaries.