• Membrane and Water Treatment
• /
• v.10 no.3
• /
• pp.201-206
• /
• 2019

In this study, we performed an electrowinning process for effective removal of metals (Cu and Ni) in solution and their recovery as solid forms. A complete removal of Cu and Ni (1,000 mg/L) was observed during four times recycling test, indicating that our electrowinning system can ensure the efficient metal removal with high stability and durability. In addition, we investigated effect of operation parameters (i.e., concentration of boric acid only for Ni, variation of pH, concentration of electrolyte ($H_2SO_4$), and cell voltage) on the efficiency of metal removal (Cu and Ni) during the electrowinning. The addition of boric acid significantly enhanced removal efficiency of Ni as the concentration of boric acid increased up to 10 g/L. Compared to negligible pH effect (pH 1, 2, and 4) on the Cu removal, we observed the increase in removal efficiency of Ni as the pH increased from 1 to 4. The electrolyte concentration did not significantly influence the removal of Cu and Ni in this study. We also obtained great removal rates of Cu and Ni at 2.5 V and 4.0 V, which were much faster than those at lower voltages. Finally, almost 99% of each Cu and Ni (1,000 mg/L) was selectively removed from the mixture of metals by adjusting pH and addition of boric acid after the completion of Cu removal. The findings in this study can provide a fundamental knowledge about effect of important parameters on the efficiency of metal recovery during the electrowinning.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.2
• /
• pp.1-10
• /
• 2021

Lithium-ion batteries with high energy density, long cycle life and other advantages, have been widely used to energy storage systems(ESS). But as ESS fires frequently occur, the safety concern has become the main obstacle that hinders the large-scale applications of lithium-ion batteries. Especially, thermal runaway is the key scientific problem in battery safety research. Therefore, in this study, we performed a numerical analysis on the thermal runaway phenomenon of NCM111, NCM523 and NCM622 batteries using a two-dimensional analysis model. The results show that the two-dimensional simulation results are generally matched with three-dimensional simulation. Also, In the case of NCM111 with a low Ni content in the temperature range used in this study, thermal runaway phenomenon does occurred very slowly, but as the Ni content is increased, the thermal runaway phenomenon occurs rapidly and the thermal stability tends to be decreased. And, in NCM523 and NCM622 batteries, chain reactions occur almost simultaneously, but in the case of NCM111 battery, it is found that after the SEI(Solid Electrolyte Interface) layer decomposition reaction, the cathode-electrolyte reaction is appeared sequentially. After that, the anodic decomposition reaction is increased and leads to the thermal runaway reaction.

• Journal of Electrochemical Science and Technology
• /
• v.8 no.4
• /
• pp.265-273
• /
• 2017

Solid-state alkaline water electrolysis is a promising method for producing hydrogen using renewable energy sources such as wind and solar power. Despite active investigations of component development for anion exchange membrane water electrolysis (AEMWE), understanding of the device performance remains insufficient for the commercialization of AEMWE. The study of assembled AEMWE devices is essential to validate the activity and stability of developed catalysts and electrolyte membranes, as well as the dependence of the performance on the device operating conditions. Herein, we review the development of catalysts and membranes reported by different AEMWE companies such as ACTA S.p.A. and Proton OnSite and device operating conditions that significantly affect the AEMWE performance. For example, $CuCoO_x$ and $LiCoO_2$ have been studied as oxygen evolution catalysts by Acta S.p.A and Proton OnSite, respectively. Anion exchange membranes based on polyethylene and polysulfone are also investigated for use as electrolyte membranes in AEMWE devices. In addition, operation factors, including temperature, electrolyte concentration and acidity, and solution feed methods, are reviewed in terms of their influence on the AEMWE performance. The reaction rate of water splitting generally increases with increase in operating temperature because of the facilitated kinetics and higher ion conductivity. The effect of solution feeding configuration on the AEMWE performance is explained, with a brief discussion on current AEMWE performance and device durability.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.4
• /
• pp.727-732
• /
• 2006

The object of this study was to investigate the influence of composition and concentration of electrolyte, ratio of cation to anion exchange resin of mixed ion exchange column in the performance of ion exchange. Also this work examined the removal capability of suspended solids by ion exchange resin and the effect of particule on the characteristics of ion exchange. Breakthrough time was extended as the amount of ions and particles present in liquid was decreased. The case of anion, the breakthrough sequence is $Cl^{-}, but the case of cation, the breakthrough sequence is $Na^{+}. As for the ratio of cation to anion exchange resin of 1:2, the breakthrough time was prolonged compared with that of 1:1 and 1:3. For the electrolyte of equal concentration containing suspended solid, breakthrough time was contracted less than 20%. It results in the increase in the removal capacity of cation exchange resin. For the higher ratio of cation exchange resin, suspended solids are shorten the cation's breakthrough time so that the runtime of ion exchange resin tower is increased.

• Korean Journal of Materials Research
• /
• v.11 no.4
• /
• pp.283-289
• /
• 2001

Composite cathodes of 50/50 vol% LSM- YSZ (La$_{1-x}$Sr$_{x}$MnO$_3$-yttria stabilized zirconia) were deposited onto surface- Polished YSZ electrolytes by colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and studied by ac impedance spectroscopy (IS). The typical impedance spectra measured for an air/LSM- YSZ/YSZ/Pt/air cell at $700^{\circ}C$ were composed of two depressed arcs. Addition of YSZ to the LSM electrode significantly enlarged the triple-phase boundaries (TPB) length inside the electrode, which led to a pronounced decrease in cathodic resistivity of LSM-YSZ composite electrodes. Polishing the electrolyte surface to eliminate the influences of surface impurities and to enlarge the TPB length can further reduce cathode resistivity. The cathodic resistivity of the LSM- YSZ electrodes was a strong function of operation temperature, composition and particle size of cathode materials, applied current, and electrolyte surface roughness.

• Korean Chemical Engineering Research
• /
• v.50 no.1
• /
• pp.93-105
• /
• 2012

Activity coefficients and solubilities of L-Valine and L-Proline in aqueous solutions containing each of four electrolytes such as NaCl, KCl, $NaNO_3$ and $KNO_3$ were measured at 298.15 K. The measurements of activity coefficients were carried out in the electrochemical cell coupled with two ion-selective electrodes (cation and anion), and the solubilities were measured by the gravimetric analysis of saturated solutions in equilibrium with the solid phase of amino acid. The measured activity coefficients of electrolytes and amino acids were correlated with the theoretical thermodynamic model presented in the previous work [Korean Chem. Eng. Res. 48(4), 519(2010)]. It was found that the activity coefficients of amino acids and electrolytes described based on the our previous model were well agreeable with experimental data. Also the experimental solubility data of L-Valine and L-Proline were successfully correlated with the thermodynamic relation mentioned in the previous work.

• Journal of the Korean Ceramic Society
• /
• v.53 no.5
• /
• pp.500-505
• /
• 2016

Scandia-stabilized zirconia co-doped with $CeO_2$ is a promising electrolyte for intermediate temperature SOFC, but still shows rapid degradation during a long-term operation. In this study, $CeO_2$ (1 mol%) as a stabilizer is partially substituted with lanthanum oxides ($M_2O_3$, M=Yb, Gd, Sm) to stabilize a cubic phase and thus durability in reducing atmosphere. 0.5M0.5Ce10ScSZ electrolytes were prepared by solid state reaction and sintered at $1450^{\circ}C$ for 10 h to produce dense ceramic specimens. With addition of the lanthanum oxide, 0.5M0.5Ce10ScSZ showed lower degradation rates than 1Ce10ScSZ. Since $Gd_2O_3$ showed the highest ionic conductivity among the co-dopants, an electrolyte-supported cell with 0.5Gd0.5Ce10ScSZ was prepared to compare its long-term performance with that of 1Ce10ScSZ-based cell. Maximum power density of 0.5Gd0.5Ce10ScSZ-based cell was degraded by about 2.3% after 250 h, which was much lower than 1Ce10ScSZ-based cell (4.2%).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.7
• /
• pp.665-671
• /
• 2017

The alkali-Metal Thermal-to-electric Converter (AMTEC) is one of the promising static energy conversion technologies for the direct conversion of thermal energy to electrical energy. The advantages over a conventional energy converter are its high theoretical conversion efficiency of 40% and power density of 500 W/kg. The working principle of an AMTEC battery is the electrochemical reaction of the sodium through an ion conducting electrolyte. Sodium ion pass through the hot side of the beta"-alumina solid electrolyte (BASE) primarily as a result of the pressure difference. This pressure difference across the BASE has a significant effect on the overall performance of the AMTEC system. In order to build the high pressure difference across the BASE, hermeticity is required for each joined components for high temperature range of $900^{\circ}C$. The AMTEC battery was manufactured by utilizing robust joining technology of BASE/insulator/metal flange interfaces of the system for both structural and electrical stability. The electrical potential difference between the anode and cathode sides, where the electrons emitted from sodium ionization and recombined into sodium, was characterized as the open-circuit voltage. The efforts of technological improvement were concentrated on a high-power output and conversion efficiency. This paper discusses about the joining and performance of the AMTEC systems.

• Applied Chemistry for Engineering
• /
• v.17 no.6
• /
• pp.575-579
• /
• 2006

Solid electrolyte interface is formed on a carbon electrode used as an anode in Li-ion battery, which can be of $Li^{+}$ intercalation/deintercalation during the first cycle. The passivation film formed by a solvent decomposition during the initial charge process affects cell performance and it was one of the main reason of an initial irreversible capacity. This paper describes the use, for the first time, of $Li_2CO_3$ as the additive for the formation of a passivation film on the carbon surface to suppress the initial irreversible reaction. Chronopotentiometry, cyclic voltammetry, and impedance spectroscopy were used to investigate the effects of the $Li_{2}CO_{3}$ additive. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction were also used to monitor changes in the surface morphology and composition of the passivation film formed by solvent decomposition and the precipitation of $Li_{2}CO_{3}$. The addition of $Li_{2}CO_{3}$ to a solution of 1 M $LiPF_{6}$/EC:MA (1:3, v/v) resulted in a decrease in the initial irreversible capacity and it was due to the suppression of the solvent decomposition on the electrode surface.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.1
• /
• pp.116-123
• /
• 2019

Thermal batteries are also called molten-salt batteries as the electrolyte is mainly composed of molten salt. The molten-salt electrolyte is a solid that does not conduct electricity at room temperature, but when it is melted by a pyrotechnic heat source, it becomes an excellent ionic conductor. Thermal batteries are a kind of pyrotechnic battery because they operate only when the solid electrolyte is melted by the heat energy provided by pyrotechnic materials. Pyrotechnic components used in a thermal battery include heat sources, fuse strips, and an igniter. The reliability of these pyrotechnic components critically affects the reliability and performance of the battery that must supply electricity stably to guided munitions even under extreme environmental conditions. Different igniter types offer different advantages: notch-type igniters offer improved ignition probability, whereas film-type igniters offer improved safety. The addition of metal oxides to the heat paper could improve the burn rate, and the ignition reliability could be greatly improved by using it with a flame igniter at the same time. Using a two-step reduction process, high-purity Fe particles in coral form can be safely obtained.