• 한국표면공학회지
• /
• 제52권6호
• /
• pp.326-333
• /
• 2019

The microporous carbon derived from PVDC-resin by a simple heat-treatment under an inert atmosphere exhibits a reasonable specific capacitance for a supercapacitor's electrode. However, the capacitance was rapidly decreased at high charge/discharge rate. The micropores present in an electrode surface hinder the entrance of an electrolyte ion onto the entire surface. To induce the meso-sized pores during the carbonization of PVDC-resin, Mg(OH)₂ was utilized as a hard template. The porous carbon made from the mixture of PVD-Cresin and Mg(OH)₂ include mesopores as well as micropores. The induced mesopores does not homogeneously distributed on the entire surface of the synthesized carbon. The PVDC-resin and Mg(OH)₂ are dissolved in the dimethylformamide for the hard template to evolve the pores on the synthesized carbon uniformly. The carbon made from PVDC-resin with solvent and a hard template contains mostly mesopores resulting in the high power performance. The reduced amount of solvent in the precursor derives the carbon with high specific surface area and high power density.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
• /
• pp.2022-2024
• /
• 2005

Electrical double-layer capacitor (EDLC) is an electrochemical energy storage device in which electric charges only accumulated by a pure electrostatic attraction force are stored on the electrolyte-electrode interface in a form of double layer and separated by the electrolyte. The composite was prepared by mixing nanosize $TiO_2$ and activated carbon through a means of ultrasonic vibration in ethanol solution for 30 min in various mass ratios of $AC:TiO_2$ to form activated carbone-semiconducting oxide composites. Either 1.0 M $LiClO_4/EC-DEC$ or $Et_4NBF_4$/EC-DEC was used as the electrolyte. It was found that with modification of $TiO_2$, the specific capacitance of activated carbon measured at $1mA/cm^2$ was increased from 40 to 50 F/g. This method is unique in comparison the conventional method because it uses semiconducting TiO2 other than electrochemically active materials such as $RuO_2$. The increase in specific capacitance could be attributed to the decrease in electric polarization, caused by the introduction of $RuO_2$.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.272-272
• /
• 2013

The attractive features of photosynthetic reaction center proteins for energy application make them useful in solar energy conversion to hydrogen fuel or electrical energy. Almost unity charge separation quantum yield and its rapid speed of ~1ns, absorbance region in visible light (480~740 nm) and high proportion of photosynthetically active solar energy of 48.5% allowed photosystem1 to exploited as a bio-material for photo-energy devices. Directionality of photosystem1 in electron transfer can solve main problem in two-step water splitting process where back reaction deteriorates the overall efficiency. In the study, photosystem1 was extracted from spinach and the photo-induced excited electron in the reaction center was utilized in various field of light energy application. First, hydrogen evolving system realized by photodeposition of platinum at the end of the electron transfer chain, with combining specific semiconductor to oxidize water in the first step of Z-scheme. The evaluation by gas-chromatography demonstrated hydrogen evolution through the system. For the further application of photoelectrical material on electrode, photosystem1 have been controlled by copper ion, which is expected to assemble photosystem in specific orientation followed by maximized photoelectrical ability of film. The research proposed concrete methods for combining natural protein and artificial materials in one system and suggested possibility of designing interface between biological and inorganic materials.

• 한국가시화정보학회지
• /
• 제19권1호
• /
• pp.50-56
• /
• 2021

With the advances in recent nanotechnology, mass transport phenomena have been receiving large attention both in academic researches and industrial applications. Nonetheless, it is not clearly determined which parameters are dominant at nanoscale mass transport. Especially, membrane is a kind of technology that use a selective separation to secure fresh water. The development of great separation membrane and membrane-based separation system is an important way to solve existing water resource problems. In this study, glass fiber-based membranes which are treated by graphene oxide (GO), poly-styrene sulfonate (GOP) and sodium dodecyl sulfate (GPS) were fabricated. Mass transport parameters were investigated in terms of material-specific and structure-specific dominance. The 3D structural information of GO, GOP, and GPS was obtained by using synchrotron X-ray nano tomography. In addition, electrostatic characteristic and water absorption rate of the membranes were investigated. As a result, we calculated internal structural information using Tomadakis-Sotrichos model, and we found that manipulation of surface characteristics can improve spacer arm effect, which means enhancement of water permeability by control length of ligand and surface charge functionality of the membrane.

• 한국융합학회논문지
• /
• 제10권7호
• /
• pp.191-198
• /
• 2019

본 연구에서는 한국의 스포츠 지도자 중에서 축구국가대표팀 감독중에서 외국인 감독의 리더십 유형을 살펴보고자 한다. 이를 위해 감독의 재임기간 동안의 뉴스 기사들을 크롤링하고 이를 분석하였다. 본 연구의 결과는 다음과 같다. 첫째, 성공한 스포츠 지도자들이 갖추고 있는 리더십의 유형이 있는 것으로 나타났다. 둘째, 실패한 스포츠 지도자들이 갖추고 있는 리더십의 유형이 있는 것으로 나타났다. 본 연구 결과에서 나타난 리더십 유형 및 특성은 지도자들이 갖추어야 할 효과적인 리더십을 규명하여, 선수들을 지도하는데 있어 필요한 리더십이 무엇인지를 파악하고 이를 통해 선수들을 지도하고 성과를 창출하는데 활용이 가능하다는 점에서 실무적 차원의 시사점이 있다.

• 대한금속재료학회지
• /
• 제49권5호
• /
• pp.419-424
• /
• 2011

Carbon nanotubes (CNTs) were directly synthesized on a copper (Cu) plate as a current collector by the catalytic thermal vapor deposition method for an electric double-layer capacitor (EDLC) electrode. The diameters of vertically aligned CNTs grown on the Cu plate were 20~30 nm. From cyclic voltammetry (CV) results, the CNTs/Cu electrode showed high specific capacitance with typical profiles of EDLCs. Rectangularshaped CV curves suggested that the CNTs/Cu electrode could be an excellent candidate for an EDLC electrode. The specific capacitances were in a range of 25~75 F/g with a scan rate of 10~100 mV/s and KOH electrolyte concentration 1~6 M, and were maintained up to 1000 charge/discharge cycles due to strong adhesion between the Cu substrate and the CNTs.

• 한국전기전자재료학회논문지
• /
• 제36권2호
• /
• pp.175-185
• /
• 2023

A hybrid supercapacitor is a promising energy storage device in view of its excellent capacitive performance. Commercial three-dimensional foam nickel (Ni) can be used as an ideal framework due to an interconnected network structure. However, its application as an electrode material for supercapacitors is limited due to its low specific capacity. Herein, we report a successful growth of MnO₂ on the surface of graphene by a one-step hydrothermal method; thus, forming a three-dimensional MnO₂-graphene-Ni hybrid foam. Our results show that the mixed structure of MnO₂ with nanoflowers and nanorods grown on the graphene/Ni foam as a hybrid electrode delivers the maximum specific capacitance of 193 F·g^-1 at a current density 0.1 A·g^-1. More importantly, the hybrid electrode retains 104% of its initial capacitance after 1,000 charge-discharge cycles at 1 A·g^-1; thus, showing the potential application as a stable supercapacitor electrode.

• Advances in Energy Research
• /
• 제8권1호
• /
• pp.41-57
• /
• 2022

Electrochemical double-layer capacitors (EDLCs) based on solid polymer electrolytes (SPEs) have gained an immense recognition in the present world due to their unique properties. This study is about preparing and characterizing EDLCs using a natural rubber (NR) based SPE with natural graphite (NG) electrodes. NR electrolyte was consisted with 49% methyl grafted natural rubber (MG49) and zinc trifluoromethanesulfonate ((Zn(CF₃SO₃)₂-ZnTF). It was characterized using electrochemical impedance spectroscopy (EIS) test, dc polarization test and linear sweep voltammetry (LSV) test. NG electrodes were made using a slurry of NG and acetone. EIS test, cyclic voltammetry (CV) test and galvanostatic charge discharge (GCD) test have been done to characterize the EDLC. Optimized electrolyte composition with NR: 0.6 ZnTF (weight basis) exhibited a conductivity of 0.6 x 10^-4 Scm^-1 at room temperature. Conductivity was predominantly due to ions. The electrochemical stability window was found to be from 0.25 V to 2.500 V. Electrolyte was sandwiched between two identical NG electrodes to fabricate an EDLC. Single electrode specific capacitance was about 2.26 Fg^-1 whereas the single electrode discharge capacitance was about 1.17 Fg^-1. The EDLC with this novel NR-ZnTF based SPE evidences its suitability to be used for different applications with further improvement.

• E2M - 전기 전자와 첨단 소재
• /
• 제7권4호
• /
• pp.317-324
• /
• 1994

In this study, new preparation method of LiCoO$_{2}$ was applied to develop cathode active material for Li rechargeable cell, and followed by X-ray diffraction analysis, electrochemical properties and initial charge/discharge characteristics as function of current density. HC8A72- and CC9A24-LiCoO$_{2}$ were prepared by heating treatment of the mixture of LiOH H$_{2}$O/CoCO$_{3}$(1:1 mole ratio) and the mixture of Li$_{2}$CO$_{3}$/CoCO$_{3}$(1:2 mole ratio) at 850 and 900.deg. C, respectively. Two prepared LiCoO$_{2}$s were identified as same structure by X-ray diffraction analysis. a and c lattice constant were 2.816.angs. and 14.046.angs., respectively. The electrochemical potential of CFM-LiCoO$_{2}$(Cyprus Foote Mineral Co.'s product), HC8A72-LiCoO$_{2}$ and CC9A24 LiCoO$_{2}$ electrode were approximately between 3.32V and 3.42V vs. Li/Li reference electrode. Stable cycling behavior was obtained during the cyclic voltammetry of LiCoO$_{2}$ electrode. According as scan rate increases, cathodic capacity decreases, but redox coulombic efficiency was about 100% at potential range between 3.6V and 4.2V vs. Li/Li reference electrode. Cathodic capacity of HC8A72-LiCoO$_{2}$ was 32% higher than that of CFM-LiCoO$_{2}$ and that of CC9A24-LiCoO$_{2}$ was 47% lower than that of CFM-LiCoO$_{2}$ at 130th cycle in the condition of lmV/sec scan rate. Constant cur-rent charge/discharge characteristics of LiCoO$_{2}$/Li cell showed increasing Ah efficiency with initial charge/discharge cycle. Specific discharge capacities of CFM and HC8A72-LiCoO$_{2}$ cathode active materials were about 93mAh/g correspondent to 34% of theretical value, 110mAh/g correspondent to 40% of theretical value, respectively. In the view of reversibility, HC8A72-LiCoO$_{2}$ was also more excellent than CFM- and CC9A24-LiCoO$_{2}$.

• 한국산학기술학회논문지
• /
• 제14권1호
• /
• pp.369-377
• /
• 2013

현재 전기자동차와 신재생에너지전원의 출력안정화에 필수적인 2차전지가 개발되고 있고, 2차전지의 효율적인 운용을 위하여 상태감시 기술과 수명예측 기술이 요구되고 있다. 기존의 2차전지 상태감시 방법으로는 전압과 비중에 의한 충전상태평가 방법 등이 있으나, 이 방법은 온도에 따라 변화되는 전압과 비중의 특성을 고려할 수 없는 한계점을 가지고 있다. 즉, 2차전지의 SOC를 평가하기 위해서는 전지 케이스 내부의 전해액 온도에 따라 달라지는 비중 값을 측정해야 하지만, 대부분의 2차전지는 밀폐형으로 보급되고 있어서 전해액의 상태를 파악하기 어려운 실정이다. 따라서 본 논문에서는 전지내부의 온도를 보정하는 열전달식을 유도함으로 정확한 SOC평가 알고리즘을 제시하였다. 또한 2차전지의 수명 예측 방법으로는 내부저항 측정 또는 잔존 용량 측정 등의 수명 예측 방법들이 있으나, 충 방전상태와 충전 후 방치시간, 사용 환경 등 여러 가지 요인에 의해 2차전지의 수명을 정확하게 판단하기 어렵다. 따라서 상기의 문제점을 해결하기 위해 $20^{\circ}C$로 환산된 비중 값에 대하여 전지의 충 방전에 대한 비중누적 값을 계산함으로 충 방전 사이클을 판정하는 수명예측 알고리즘을 제시하였다. 상기에서 제시한 알고리즘을 바탕으로 시험 장치를 제작하여 다양한 시뮬레이션을 수행한 결과, 기존의 방법에 비하여 본 논문에서 제안한 알고리즘이 정확한 연축전지의 상태감시 및 수명예측에 대한 결과를 얻을 수 있음을 확인하였다.