MnO₂-HCS 복합체를 이용한 슈퍼커패시터의 전기화학적 특성

김은미,정상문,Jin, En Mei,Jeong, Sang Mun 한국청정기술학회 2018 청정기술 Vol.24 No.3

중공형 구형 탄소(hollow carbon spheres, HCS) 또는 구형 탄소(carbon spheres, CS)는 수열합성법에 의해 제조되었고 $MnO_2$를 증착하기 위한 탄소 지지체로 사용하였다. $MnO_2$는 화학적 레독스 증착법에 의해 HCS 또는 CS 표면에 증착하였다. 화학적 산화환원 증착법은 미립자 지지체의 표면에 다른 산화물 합성에 특히 효과적이다. $MnO_2$는 HCS 또는 CS의 표면에 일정한 슬릿 모양의 분포를 보였고 HCS 표면에서 보다 엉성한 슬릿 모양의 $MnO_2$ 입자가 생성되었다. $MnO_2-HCS$는 $20mv\;s^{-1}$의 스캔 속도에서 초기 사이클에서 약 $164.1F\;g^{-1}$의 정전용량을 나타내었고 1000 사이클 후에는 약 $141.3F\;g^{-1}$의 정전용량을 나타내었다. 1000 사이클 기준으로 $MnO_2-HCS$와 $MnO_2-CS$는 각각 86%와 78%의 용량유지율을 나타내었다. 이것은 HCS 표면에서 엉성한 슬릿모양의 $MnO_2$의 성장이 전해질의 흐름 및 전해질 내의 $Na^+$ 이온의 흡탈착이 보다 용이하여 나타난 결과로 생각된다. Hollow carbon spheres (HCS) and carbon spheres (CS) were prepared by a hydrothermal reaction and they were introduced as a substrate for the deposition of $MnO_2$ nanoparticles. The $MnO_2$ nanoparticles were deposited on the carbon surface by a chemical redox deposition method. After deposition, the $MnO_2$ nanoparticles were uniformally distributed on the carbon surface in a slit-shape, and sparse $MnO_2$ slits appeared on the HCS surface. The $MnO_2-HCS$ showed an initial specific capacitance of $164.1F\;g^{-1}$ at scan rate of $20mv\;s^{-1}$, and after 1,000 cycles, the specific capacitance was maintained to $141.3F\;g^{-1}$. The capacity retention of $MnO_2-HCS$ and $MnO_2-CS$ were calculated to 86% and 78% in the cycle performance test up to 1,000 cycles, respectively. $MnO_2-HCS$ showed a good cycle stability due to the mesoporous hollow structure which can cause a faster diffusion of the electrolyte and can easily adsorb and desorb $Na^+$ ions on the surface of the electrode.

분산특성이 향상된 고효율 염료감응형 태양전지

김은미,박경희,구할본,박복기,Jin, En-Mei,Park, Kyung-Hee,Gu, Hal-Bon,Park, Bok-Kee 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.6

$TiO_2$ nano-particle paste was prepared by ethyl cellulose, $\alpha$-terpineol and bis(2-ethylhexyl) phthalate (dioxcyl phthalate) for dye-sensitized solar cells (DSSCs). Dispersion and absorbance of $TiO_2$ photoanode films was controlled by adding different amount of ethyl cellulose and $\alpha$-terpineol. The morphology of prepared $TiO_2$ films was studied by field emission scanning electron microscopy (FE-SEM) and the optical properties of $TiO_2$ films were measured by UV/vis spectra. Photovoltaic-current density was observed to determine the electrochemical response of DSSCs. Energy conversion efficiency was obtained about 7.1% at ethyl cellulose and $\alpha$-terpineol at optimal mixed ratio (as ethyl cellulose: 0.1 g; $\alpha$-terpineol: 1.5 ml) under illumination with AM 1.5($100\;Wcm^{-2}$) simulated sunlight.

TiO2 광전극의 광산란 특성을 이용한 염료감응형 태양전지

김은미 ( En Mei Jin ),박경희 ( Kyung Hee Park ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2010 공학기술논문지 Vol.3 No.2

In this study, we increase the solar conversion efficiency of DSSC (dye-sensitized solar cell) using nanocrystalline TiO2 semiconductor. We preparation of TiO2 photoelectrode, assembly the DSSC and put a focus in analyses electrochemical properties of DSSC by using quartz glass powder in TiO2 photoelectrode to increase light scattering effect and improved conversion efficiency. Morphology of the photoelectrode was investigate using field emission scanning electron microscopy (FE-SEM) and photovoltaic properties was examined under illumination with AM 1.5 simulated sunlight. The results showed 146% power conversion efficiency when the optimal content of quartz glass powder was 5 wt.% than another content.

MnO₂-HCS 복합체를 이용한 슈퍼커패시터의 전기화학적 특성

김은미(En Mei Jin),정상문(Sang Mun Jeong) 한국청정기술학회 2018 청정기술 Vol.24 No.3

중공형 구형 탄소(hollow carbon spheres, HCS) 또는 구형 탄소(carbon spheres, CS)는 수열합성법에 의해 제조되었고 MnO₂를 증착하기 위한 탄소 지지체로 사용하였다. MnO₂는 화학적 레독스 증착법에 의해 HCS 또는 CS 표면에 증착하였다. 화학적 산화환원 증착법은 미립자 지지체의 표면에 다른 산화물 합성에 특히 효과적이다. MnO₂는 HCS 또는 CS의 표면에 일정한 슬릿 모양의 분포를 보였고 HCS 표면에서 보다 엉성한 슬릿 모양의 MnO₂ 입자가 생성되었다. MnO₂-HCS는 20 mv s<SUP>-1</SUP>의 스캔 속도에서 초기 사이클에서 약 164.1 F g<SUP>-1</SUP>의 정전용량을 나타내었고 1000 사이클 후에는 약 141.3 F g<SUP>-1</SUP>의 정전용량을 나타내었다. 1000 사이클 기준으로 MnO₂-HCS와 MnO₂-CS는 각각 86%와 78%의 용량유지율을 나타내었다. 이것은 HCS 표면에서 엉성한 슬릿모양의 MnO₂의 성장이 전해질의 흐름 및 전해질 내의 Na⁺ 이온의 흡탈착이 보다 용이하여 나타난 결과로 생각된다. Hollow carbon spheres (HCS) and carbon spheres (CS) were prepared by a hydrothermal reaction and they were introduced as a substrate for the deposition of MnO₂ nanoparticles. The MnO₂ nanoparticles were deposited on the carbon surface by a chemical redox deposition method. After deposition, the MnO₂ nanoparticles were uniformally distributed on the carbon surface in a slit-shape, and sparse MnO₂ slits appeared on the HCS surface. The MnO₂-HCS showed an initial specific capacitance of 164.1 F g<SUP>-1</SUP> at scan rate of 20 mv s<SUP>-1</SUP>, and after 1,000 cycles, the specific capacitance was maintained to 141.3 F g<SUP>-1</SUP>. The capacity retention of MnO₂-HCS and MnO₂-CS were calculated to 86% and 78% in the cycle performance test up to 1,000 cycles, respectively. MnO₂-HCS showed a good cycle stability due to the mesoporous hollow structure which can cause a faster diffusion of the electrolyte and can easily adsorb and desorb Na+ ions on the surface of the electrode.

염료감응 태양전지의 염료 흡착 특성 향상에 관한 연구

김은미 ( En Mei Jin ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2011 공학기술논문지 Vol.4 No.2

The acid treatment have been used for nanocrystalline TiO2 particles. It ha been observed that nitric acid treatment can enhance transparency of thin films a well as higher level of dispersion of nanoparticles. HNO3 treated surfaces has showed higher surface area and increase in hydroxy functional groups at TiO2 photoelectrode film surfaces was observed. This process has allowed to increase the conversion efficiency of solar cell which is possibly due to higher amount of dye adsorption. These process have significantly enhanced the efficiency of DSCs for developing high sensitivity. The efficiency increased upto 11 8% and this is observed at non nitric acid treatment of TiO2 photoelectrode.

상용 고용량 리튬이온이차전지용 NCA 양극활물질의 전기화학적 특성

김은미 ( En Mei Jin ),이가을 ( Ga-eul Lee ),나병기 ( Byuong-ki Na ),정상문 ( Sang Mun Jeong ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.2

LiNi_1-x-yCo_xAl_yO₂(x=0.15, y=0.045 혹은 0.05, NCA) 양극소재의 전기화학적 특성 및 양극소재의 입자 크기 분포에 대한 리튬이온이차전지의 수명특성에 대한 영향을 살피기 위해 두 종의 상업용 NCA (NCA#1, NCA#2) 양극소재를 리튬이온이차전지의 양극으로 사용하였다. NCA#1은 약 5 μm의 균일한 구형의 입자로 구성되어 있고 NCA#2는 약 5 μm와 11 μm 정도의 입자들이 혼합되어 있는 분말이다. 충방전 측정 결과 NCA#2는 초기 방전용량은 197.0 mAh/g으로 NCA#1에 비해 높게 나타났다. NCA#1과 NCA#2의 용량 유지율(30사이클 기준)은 각각 92%와 94%로 나타났다. In order to investigate the electrochemical properties and the particle size effect of LiNi_1-x-yCo_xAl_yO₂ (x=0.15, y=0.045 or 0.05, NCA) for lithium ion batteries (LIBs), two commercial NCA cathode materials (NCA#1, NCA#2) were used as cathode materials for LIB. The average particle size of the NCA#1 which consisted of uniform spherical particles was found to be approximately 5 μm. NCA#2 consisted of particles with bimodal size distribution of approximately 5 μm and 11 μm. From the results of charge-discharge performance test, a high initial discharge capacity of 197.0 mAh/g was obtained with NCA#2, which is a higher value than that with NCA#1. The cycle retentions of NCA#1 and NCA#2 up to 30 cycles were 92% and 94%, respectively.

수열합성한 TiO2을 이용한 염료감응형 태양전지의 전기화학적 특성

김은미 ( En Mei Jin ),왕만림 ( Wan Lin Wang ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2013 공학기술논문지 Vol.6 No.1

In this study, the TiO2 was prepared by hydrothermal reactions; and 0.5 M, 1.0 M and 2.0 M TTIP were added. The different contents of TTIP added TiO2 are studied by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and photocurrent density-voltage test. The photovoltaic properties under illumination with AM 1.5 simulated under sunlight. In the results, the XRD patterns index to single-phase material having an anatage structure and the particle size of 1.0 M TTIP added TiO2 is 7.61 nm. Using the 1.0 M TTIP added TiO2 demonstrates a higher solar conversion efficiency than the other samples. We got 114% and 131% enhanced power conversion efficiency when the optimal content of TTIP.

리튬 폴리머 전지용 정극활물질 LiFePO4 및 LiM(x)Fe(1-x)PO4의 전기화학적 특성

김은미 ( En Mei Jin ),박경희 ( Kyung Hee Park ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2009 공학기술논문지 Vol.2 No.2

Phospho-olivine LiFePO4 and LiTi0.1Fe0.9PO4 calhode materials were prepared by the solid-state reaction at the different temperature (550, 600 and 650℃). To improve conductivity carried out Ti2+ doped LiFeP04 and we studied the effect of electrochemical performance. At the different heating temperature resulted in the didn``t appearance of impurity phase which was shown by high resolution X-ray diffraction and perepared by 600℃ temperature``s discharge performance results exhibited an excellent high capacity of 140 mAh/g at the first cycle, and 139 mAh/g after 50 cycles. The Ti2+ doped LiFeP04 started 3.36 V of flat voltage on discharge curve and showed a gentle decline in the curve compared to undoped LiFeP04 without great changes of capacity. And so, we could achieve to improve electrochemical performance as reversible, cycle life. Similarly, LiFePO4 doping with Ti2+ showed the effect of dopant which is the improved discharge capacity as 140 mAh/g and good cycling performance.

염료감응형 태양전지의 광전기적 특성 개선을 위한 금속산화물 나노파이버의 응용

동영상(Yong Xiang Dong),김은미(En Mei Jin),정상문(Sang Mun Jeong) 한국청정기술학회 2018 청정기술 Vol.24 No.3

염료감응형 태양전지의 광전변환효율(η) 향상을 위하여 수열합성한 TiO₂ 나노입자에 전기방사한 TiO₂, SiO₂, ZrO₂ 및 SnO₂ 나노파이버를 첨가하여 광전극에 적용하였다. TiO₂ 나노파이버를 첨가한 염료감응형 태양전지는 순수한 TiO₂ 나노입자에 비해 높은 전류밀도(Jsc)를 나타내었고 이것은 나노파이버 구조로 인하여 염료에서 여기된 전지의 전달 특성이 용이하여 나타난 현상으로 생각된다. 또한 SiO₂ 나노파이버를 첨가한 염료감응형 태양전지의 경우, 순수한 TiO₂ 나노입자를 이용한 것에 비해 보다 높은 0.67 V의 개방전압(Voc)을 나타내었고 에너지 변환효율 또한 6.24%로 가장 높게 나타났다. In order to improve the photo conversion efficiency (η) of dye-sensitized solar cells (DSSCs), the electrospun TiO₂, SiO₂, ZrO₂ and SnO₂ nanofibers were added into the hydrothermally prepared TiO₂ nanoparticles for application to a photoelectrode for DSSCs. The TiO₂ nanofiber added photoelectrode exhibited a higher photo current density (Jsc) compared to the bare TiO₂ nanoparticles, which is caused from acceleration of the transfer of excited electron from dye molecule due to the nanofiber structure. The DSSCs with SiO₂ nanofibers shows a higher open circuit voltage (Voc) of 0.67 V and the highest photo conversion efficiency was found to be 6.24%.

도핑효과에 따른 리튬이차전지용 NCA 양극활물질의 전기화학적 특성 향상

범지우 ( Zhi Yu Fan ),김은미 ( En Mei Jin ),정상문 ( Sang Mun Jeong ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.6

니켈 함량이 높은 리튬이차전지용 NCA 양극소재의 용량 및 수명특성을 향상시키기 위하여 붕소와 코발트를 상업용Li_1.06Ni_0.91Co_0.08Al_0.01O₂ (NCA)에 도핑하여 리튬이차전지의 양극소재로 사용하였다. 상업용 NCA 양극소재는 약 5 μm와 12 μm 크기의 2차 입자들이 혼합되어 있고 붕소와 코발트 도핑후 입자크기는 조금 감소되었다. 붕소와 코발트를 도핑한 NCA-B와 NCA-Co의 초기 방전용량은 각각 214 mAh/g과 200 mAh/g으로 도핑하지 않은 NCA에 비해 높게 나타났으며, 특히 NCA-Co는 20번째의 방전용량이 157mAh/g으로 가장 우수한 방전용량특성을 나타내었다. 이는 코발트를 도핑함으로써 c축 방향으로의 결정이 성장되어 리튬이온의 확산이 용이하기 때문이다. In order to improve the capacity and cycling stability of Ni-rich NCA cathode materials for lithium ion bat-teries, the boron and cobalt were doped in commercial Li_1.06Ni_0.91Co_0.08Al_0.01O₂ (NCA) powders. Commercial NCA par-ticles are mixed composites such as secondary particles of about 5 μm and 12 μm, and the particle size was decreased by doping boron and cobalt. The initial discharge capacities of the boron and cobalt doped NCA-B and NCA-Co were found to be 214 mAh/g and 200 mAh/g, respectively, which are higher values than that of the raw NCA cathode material. In par-ticular, NCA-Co exhibits the best discharge capacity of 157 mAh/g after 20 cycles, which is probably due to the enhanced diffusion of lithium ion by crystal growth along with the c-axis direction.