• Korean Journal of Materials Research
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• v.24 no.6
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• pp.285-292
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• 2014

Commercial activated-carbon used as the electrode material of an electric double-layer capacitor (EDLC) was posttreated with various acids and alkalis to increase its capacitance. The carbon samples prepared were then heat-treated in order to control the amount of acidic functional groups formed by the acid treatments. Coin-type EDLC cells with two symmetric carbon electrodes were assembled using the prepared carbon materials and an organic electrolyte. The electrochemical performance of the EDLC was measured by galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Among the various activated carbons, the carbon electrodes (CSsb800) prepared by the treatments of coconutshell-based carbon activated with NaOH and $H_3BO_5$, and then heat treated at $800^{\circ}C$ under a flow of nitrogen gas, showed relatively good electrochemical performance. Although the specific-surface-area of the carbon-electrode material ($1,096m^2/g$) was less than that of pristine activated-carbon ($1,122m^2/g$), the meso-pore volume increased after the combined chemical and heat treatments. The specific capacitance of the EDLC increased from 59.6 to 74.8 F/g (26%) after those post treatments. The equivalent series resistance of EDLC using CSsb800 as electrode was much lower than that of EDLC using pristine activated carbon. Therefore, CSsb800 exhibited superior electrochemical performance at high scan rates due to its low internal resistance.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.883-889
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• 2014

It is generated for cavitation erosion due to the local static boiling by pressure differentials in high speed rotating fluid environment. The cavitation is influenced by various elements such as pressure, velocity, temperature, pH of fluid and medium. In particular, the damage of material is accelerated due to the electrochemical corrosion by $C1^-$ and cavitation erosion due to cavities in seawater. In this paper, hence, it investigated for martensite stainless steel the damage behavior with applied current density and cavitation time in natural seawater solution. Less damage depth at the cavitation condition was observed than static condition as a result of galvanostatic experiment. Furthermore, it was shown that dramatic increase of weightloss, damage rate and damage depth after 3 hour of cavitation test.

• Carbon letters
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• v.25
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• pp.14-24
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• 2018

Electrochemical properties and performance of composites performed by incorporating metal oxide or metal hydroxide on carbon materials based on graphene and carbon nanotube (CNT) were analyzed. From the surface analysis by field emission scanning electron microscopy and field emission transmission electron microscopy, it was confirmed that graphene, CNT and metal materials are well dispersed in the ternary composites. In addition, structural and elemental analyses of the composite were conducted. The electrochemical characteristics of the ternary composites were analyzed by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy in 6 M KOH, or $1M\;Na_2SO_4$ electrolyte solution. The highest specific capacitance was $1622F\;g^{-1}$ obtained for NiCo-containing graphene with NiCo ratio of 2 to 1 (GNiCo 2:1) and the GNS/single-walled carbon $nanotubes/Ni(OH)_2$ (20 wt%) composite had the maximum specific capacitance of $1149F\;g^{-1}$. The specific capacitance and rate-capability of the $CNT/MnO_2/reduced$ graphene oxide (RGO) composites were improved as compared to the $MnO_2/RGO$ composites without CNTs. The $MnO_2/RGO$ composite containing 20 wt% CNT with reference to RGO exhibited the best specific capacitance of $208.9F\;g^{-1}$ at a current density of $0.5A\;g^{-1}$ and 77.2% capacitance retention at a current density of $10A\;g^{-1}$.

• Journal of Electrochemical Science and Technology
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• v.11 no.3
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• pp.282-290
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• 2020

In this article, we report the effect of blended cathode materials on the performance of all-solid-state lithium-ion batteries (ASLBs) with oxide-based organic/inorganic hybrid electrolytes. LiFePO₄ material is good candidates as cathode material in PEO-based solid electrolytes because of their low operating potential of 3.4 V; however, LiFePO₄ suffers from low electric conductivity and low Li ion diffusion rate across the LiFePO₄/FePO₄ interface. Particularly, monoclinic Li₃V₂(PO₄)₃ (LVP) is a well-known high-power-density cathode material due to its rapid ionic diffusion properties. Therefore, the structure, cycling stability, and rate performance of the blended LiFePO₄/Li₃V₂(PO₄)₃ cathode material in ASLBs with oxidebased inorganic/organic-hybrid electrolytes are investigated by using powder X-ray diffraction analysis, field-emission scanning electron microscopy, Brunauer-Emmett-Teller sorption experiments, electrochemical impedance spectroscopy, and galvanostatic measurements.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.2
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• pp.87-90
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• 2008

Co-Pt alloy thin films were galvanostatically electrodeposited on Ru (30 nm)/Ta (5 nm)/Si (100) substrates from a amino-citrate based electrolyte. We used Ru(0002)-oriented buffer layers to control the crystallinity and orientation of the Co-Pt alloy thin films. The effect of solution temperature on the microstructure and magnetic properties of the Co-Pt alloy thin film was investigated. The samples were characterized by EDS, FESEM, XRD diffractometer using Cu $K{\alpha}$ radiation. The magnetic properties of these films were analyzed by a VSM and torque magnetometer. The Co-Pt alloy thin films were exhibited very high out-of-plane coercivity and squareness of the multilayer were 6527 Oe and 0.93, respectively, without heat treatment.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.243-246
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• 2006

The LiCoO2 thin films were prepared on the Pt/Ti/SiO2/Si substrate by spin coating using citrate sol. The citrate sol was spin-coated on substrate and dried at 380oC for 15 min. to evaporate the solvents and remove the organic materials. The as-deposited films were annealed at 750oC for 10 min. in air for crystallization. The X-ray diffraction patterns for the film have been indexed hexagonal system with space group R3m. The active area of LiCoO2 films for electrochemical test was about 11cm2. A Li foil and 1M LiClO4 in propylene carbonate(PC) and ethylene carbonate(EC) (1:1)were used as an anode and an electrolyte, respectively. The galvanostatic charge-discharge test was carried out at constant current density ranging from 5 A/cm2 in the voltage window between 4.2 and 3.0 V. The first discharge capacity of the film is 0.35Ah/cm2-m. The cycling behavior of the LiCoO2 film is also reported.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1200-1207
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• 2020

We have fabricated the supercapacitor composed of porous activated carbon, metal-organic framework (MOF) with polymer based solid state electrolyte as a "ion gel" and characterized its electrochemical behaviour as a function of the MOF contents. The electrochemical properties of the supercapacitor were analyzed via cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and galvanostatic charge/discharge test. As a results, the supercapacitor based on porous activated carbon/MOF composite showed the highest capacitance value at 0.5 wt% of MOF contents and decreased capacitance with increase MOF contents over the 0.5 wt%. Consequently, the porous activated carbon/MOF composite based supercapacitor is applicable to various aspect for energy storage device.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.37.1-37.1
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• 2010

The multi-component olivine cathode material, $LiMn_{1/3}Fe_{1/3}Co_{1/3}PO_4$, was prepared via a novel coprecipitation method of the mixed transition metal oxalate, $Mn_{1/3}Fe_{1/3}Co_{1/3}(C_2O_4){\cdot}2H_2O$. The stoichiometric ratio and distribution of transition metals in the oxalate, therefore, in the olivine product, was affected sensitively by the environments in the coprecipitation process, while they are the important factors in determining the electrochemical property of electrode materials with multiple transition metals. The effect of the pH, atmosphere, temperature, and aging time was investigated thoroughly with respect to the atomic ratio of transition metals, phase purity, and morphology of the mixed transition metal oxalate. The electrochemical activity of each transition metal in the olivine synthesized through this method clearly was enhanced as indicated in the cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. Three distinctive contributions from Mn, Fe, and Co redox couples were detected reversibly in multiple charge and discharge processes. The first discharge capacity at the C/5 rate was $140.5\;mAh\;g^{-1}$ with good cycle retention. The rate capability test showed that the high capacity still is retained even at the 4C and 6C rates with 102 and $81\;mAh\;g^{-1}$, respectively.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.331-335
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• 1999

The transition metal oxides have been of interest as bifunctional electrocatalysts for bifunctional air electrodes. The amorphous citrate precursor (ACP) process has been optimized to prepare perovskite (La0.6Ca0.4CoO3) and pyrochlore (Pb2Ru2O6) powders with high surface area, and consequent improvement of The electrocatalytic performance in an air electrode with thermal treatment. PTFE -bonded gas diffusion electrodes loaded with perovskitc and pyrochlore catalysts showed good bifunctional performances. The electrodes were fairly stable up to 100 hour in the galvanostatic mode at ${\pm}25mA/cm^2$, from which these electrodes offer promise as practical bifunctional air electrodes.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.680-686
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• 2013

Tungsten oxide films were prepared by an electrochemical deposition method for use as the anode in rechargeable lithium batteries. Continuous potentiostatic deposition of the film led to numerous cracks of the deposits while pulsed deposition significantly suppressed crack generation and film delamination. In particular, a crack-free dense tungsten oxide film with a thickness of ca. 210 nm was successfully created by pulsed deposition. The thickness of tungsten oxide was linearly proportional to deposition time. Compositional and structural analyses revealed that the as-prepared deposit was amorphous tungsten oxide and the heat treatment transformed it into crystalline triclinic tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium batteries. Typical peaks for the conversion processes of tungsten oxides were observed in cyclic voltammograms, and the reversibility of the heat-treated sample exceeded that of the as-prepared one. Consistently, the cycling stability of the heat-treated sample proved to be much better than that of the as-prepared one in a galvanostatic charge/discharge experiment. These results demonstrate the feasibility of using electrolytic tungsten oxide films as the anode in rechargeable lithium batteries. However, further works are still needed to make a dense film with higher thickness and improved cycling stability for its practical use.