• 한국세라믹학회지
• /
• 제45권11호
• /
• pp.662-666
• /
• 2008

Electrochemical properties of carbon cryogel electrode for the application of composite electrode materials mixed with metal oxide in supercapacitor have been studied. Carbon cryogels were synthesized by sol-gel polycondensation of resorcinol with form aldehyde, followed by a freeze drying, and then pyrolysis in an inert atmosphere. Physical properties of carbon cryogel were characterized by BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that carbon cryogel is amorphous material. The electrochemical properties of carbon cryogel were measured by cyclic voltammetry as a function of concentration of liquid electrolyte, galvanostatic charge-discharge with different scan rates and electrochemical impedance measurements. The result of cyclic voltammetry indicated that the specific capacitance value of a carbon cryogel electrode was approximately 150.2 F/g (at 5 mV/s in 6M KOH electrolyte).

• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 2003년도 추계학술대회
• /
• pp.335-343
• /
• 2003

In the electrode fabrication of unit cell, it was ascertained that electrochemical characteristics were greatly increased with 90 wt.% of BP-20, 5 wt.% of Super P and 5 wt.% of mixed binder [P(VdF-co-HFP) : PVP =7 : 3] The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of Electric Double Layer Capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. The electrochemical characteristics of 2.3 V/3,000 F grade EDLC were as follows: 0.35 m of DC-ESR (100 A discharge), 0.14 mof AC-ESR (AC amplitude 100 mV), 2.80 Wh/kg (3.73 Wh/L) of energy density and 4.64 kW /kg (6.19 kW/L) of power density. Power output was compatible with electric vehicle applications, uninterrupted power supply and engine starter, in due consideration of Ragone relations.

• 전기화학회지
• /
• 제15권3호
• /
• pp.190-197
• /
• 2012

비닐에틸렌 카보네이트(VEC: vinyl ethylene carbonate)를 전해질 첨가제로 사용했을 때 하이브리드 커패시터(hybrid capacitors) 전극에서 나타나는 전기화학적 특성변화에 대해서 고찰하였다. 하이브리드 커패시터는 양극은 활성탄(AC : activated carbon) 음극은 리튬티타늄옥사이드(LTO: $Li_4Ti_5O_{12}$)를 사용하였고, 전해질로서는 에틸렌 카보네이트(EC: ethylene carbonate): 디메틸 카보네이트 (DMC: dimethyl carbonate) : 에틸메틸 카보네이트(EMC : ethyl methyl carbonate)를 사용하였고, 염으로 육불화인산리튬($LiPF_6$: lithium hexafluoro phosphate)을 사용하였다. 전극 표면의 산소관능기 그룹을 제거하고, 표면을 환원시킴으로써 전극에 안정성을 향상시킨다고 알려진 VEC의 첨가량에 따른 전기화학적 특성을 평가하였으며, 0.7%(부피비)의 VEC첨가시, 가장 우수한 전기화학적 특성을 얻을 수 있었다. 0.7% 이상 첨가하였을 경우, 오히려 부반응 증가로 전기화학적 성능이 감소하였다. X-ray photoelectron spectrocopy (XPS) 결과로부터 LTO 전극에서 VEC가 첨가되지 않은 전해질에 비해 LiF가 감소한 것을 확인 할 수 있었다. VEC가 첨가되지 않은 전해질은 2500 사이클 후, 43.2 %의 용량 유지를 나타냈지만, 최적화된 VEC 첨가를 통하여 82.7 %의 높은 용량을 유지하는 특성을 가진 하이브리드 커패시터를 얻을 수 있었다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제8권3호
• /
• pp.56-60
• /
• 2003

전기분해에 의한 부상현상을 이용하여 유류로 오염된 토양 세정 후 발생되는 유출수 중 유분 등을 분리하기 위한 적정 운전조건을 찾고자 하였다. 전기분해 반응조(200${\times}$10${\times}$15cm)를 이용하여 혼합계면활성제($POE_5$ : $POE_{14} $, 1:1) 1%용액에 디젤을 1,000 mg/L 농도로 용해시켜 실험하였다. 양극에는 티타늄 코팅전극, 음극으로는 스테인레스 스틸전극을 이용하였다. 반응시간은 62분(반응 :60분, 부상시간 :2분)이었으며 전압은 6V였다. 전해질 첨가에 의한 영향을 알아보기 위하여 실험한 결과, 전해질을 첨가하였을 경우 첨가하지 않았을 때보다 40% 정도의 효율이 증가하였다. 적정 전해질, 주입농도 및 반응시간을 알아보기 위하여 1N NaCl과 NaOH의 농도를 변화시켜 가면서 실험하였다. NaCl의 경우 더 좋은 효율을 나타내었다. 전해질의 농도는 0.2-1.0%의 농도범위에서 NaCl와 NaOH 모두 농도에 따라 순차적으로 효율이 증가하였다. 두 전해질 모두 0.4-1.0% 농도 범위에서 평형에 도달하는 시간은 20분으로 나타났다.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2017년도 춘계학술대회 논문집
• /
• pp.149-149
• /
• 2017

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the seawater upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification showed a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• 한국재료학회지
• /
• 제23권12호
• /
• pp.695-701
• /
• 2013

To understand how reactivity between reinforcing nanoparticles and aqueous solution affects electrodeposited Cu thin films, two types of commercialized cerium oxide (ceria, $CeO_2$) nanoparticles were used with copper sulfate electrolyte to form in-situ nanocomposite films. During this process, we observed variation in colors and pH of the electrolyte depending on the manufacturer. Ceria aqueous solution and nickel sulfate ($NiSO_4$) aqueous solutions were also used for comparison. We checked several parameters which could be key factors contributing to the changes, such as the oxidation number of Cu, chemical impurities of ceria nanoparticles, and so on. Oxidation number was checked by salt formation by chemical reaction between $CuSO_4$ solution and sodium hydroxide (NaOH) solution. We observed that the color changed when $H_2SO_4$ was added to the $CuSO_4$ solution. The same effect was obtained when $H_2SO_4$ was mixed with ceria solution; the color of ceria solution changed from white to yellow. However, the color of $NiSO_4$ solution did not show any significant changes. We did observe slight changes in the pH of the solutions in this study. We did not obtain firm evidence to explain the changes observed in this study, but changes in the color of the electrolyte might be caused by interaction of Cu ion and the by-product of ceria. The mechanical properties of the films were examined by nanoindentation, and reaction between ceria and electrolyte presumably affect the mechanical properties of electrodeposited copper films. We also examined their crystal structures and optical properties by X-ray diffraction (XRD) and UV-Vis spectroscopy.

• 공업화학
• /
• 제9권4호
• /
• pp.523-528
• /
• 1998

본 연구에서는 고체전해질셀 내에서 작업전극으로 사용된 $V_2O_5$의 전기화학적 특성을 알아보기 위해 YSZ를 고체전해질로 사용하여 전기화학셀(1-Butene+$O_2$, $V_2O_5{\mid}YSZ{\mid}Ag$, $O_2$)을 구성하였다. 상대전극인 Ag는 소성에 따라 sintering이 일어나고 $3{\mu}m$ 이상의 기공을 갖는 구조를 얻었다. 작업전극은 소성조건에 따라 부분산화반응에 영향을 주는 (010)면이 발생되었다. $V_2O_5$의 1-부텐에 대한 주요생성물은 부타디엔이었고 SEP (solid electrolyte potentiometry) 기술을 이용하여 작업전극상에 흡착된 화학종의 화학포텐셜을 측정하였다. 가스조성에 따른 개로전위 (OCV; open circuit voltage)를 측정하여 표면 산소종에 혼합전위의 발생을 확인하였다.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2016년도 추계학술대회 논문집
• /
• pp.153-153
• /
• 2016

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the sea water upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Afterward, the irregular oxide film that was created in the first step surface modification was removed. For the second step surface modification process (identical to the step 1), etching was performed using mixture of chromic acid (1.8 wt.%) and phosphoric acid (6 wt.%) at $60^{\circ}C$ temperature for 30 minutes. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification presented a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• Journal of Electrochemical Science and Technology
• /
• 제14권1호
• /
• pp.85-95
• /
• 2023

In recent years, solid-state Li metal batteries (SSLBs) have attracted significant attention as the next-generation batteries with high energy and power densities. However, uncontrolled dendrite growth and the resulting pulverization of Li during repeated plating/stripping processes must be addressed for practical applications. Herein, we report a plastic-crystal-based polymer/ceramic composite solid electrolyte (PCCE) to resolve these issues. To fabricate the one-side ceramic-incorporated PCCE (CI-PCCE) film, a mixed precursor solution comprising plastic-crystal-based polymer (succinonitrile, SN) with garnet-structured ceramic (Li₇La₃Zr₂O₁₂, LLZO) particles was infused into a thin cellulose membrane, which was used as a mechanical framework, and subsequently solidified by using UV-irradiation. The CI-PCCE exhibited good flexibility and a high room-temperature ionic conductivity of over 10^-3 S cm^-1. The Li symmetric cell assembled with CI-PCCE provided enhanced durability against Li dendrite penetration through the solid electrolyte (SE) layer than those with LLZO-free PCCEs and exhibited long-term cycling stability (over 200 h) for Li plating/stripping. The enhanced Li⁺ transference number and lower interfacial resistance of CI-PCCE indicate that the ceramic-polymer composite layer in contact with the Li anode enabled the uniform distribution of Li⁺ flux at the interface between the Li metal and CI-PCCE, thereby promoting uniform Li plating/stripping. Consequently, the Li//LiFePO₄ (LFP) full cell constructed with CI-PCCE demonstrated superior rate capability (~120 mAh g^-1 at 2 C) and stable cycle performance (80% after 100 cycles) than those with ceramic-free PCCE.

• 대한안전경영과학회지
• /
• 제2권4호
• /
• pp.187-195
• /
• 2000

Electrochemical promotion of the reaction rate was investigated for CO oxidation in a solid electrolyte catalytic reactor where a thin film of Pt was deposited on the yttria stabilized zirconia as an electrode as well as a catalyst. It was shown under open circuit condition that potential was a mixed potential of $O_2$exchange reaction and electrochemical reaction induced by CO. The effect of electrochemical modification on the CO oxidation rate was studied at various overpotentials and $P_{CO}$$P_{O2}$.