• 한국분말재료학회지
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• 제12권4호
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• pp.249-254
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• 2005

Titanium dioxide was prepared by Polymer Complex Solution Method(PCSM) according to the mole ratio of Titanium (IV) isopropoxide(TTIP)/solvent and polymer(Poly Ethylene Glycol). Polymer electrolytes were usually made by dispersing preproduced ceramic nanoparticles in a polymer matrix. Using this method, pure and nano-sized $TiO_2$ powder was synthesized through a simple procedure and polymer entrapment route. At the optimum amount of the polymer, the titanium ions are dispersed in solution and a homogeneous polymeric network is formed. The maximum intensity of anatase phase of $TiO_2$ was achieved by calcining at $500^{\circ}C$ for 2h. The synthesized $TiO_2$ powders were nano-sized and the average size was about 50nm. Anatase/Rutile ratio of the synthesized $TiO_2$ was 70%/30%.

• Advances in materials Research
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• 제8권1호
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• pp.37-46
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• 2019

Electrochemical double layer capacitors (EDLCs) which are fabricated using carbon based electrodes have been emerging at an alarming rate to fulfill the energy demand in the present day world. Activated charcoal has been accepted as a very suitable candidate for electrodes but its cost is higher than natural graphite. Present study is about fabrication of EDLCs using composite electrodes with activated charcoal and Sri Lankan natural graphite as well as a gel polymer electrolyte which is identified as a suitable substitute for liquid electrolytes. Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge Discharge test were done to evaluate the performance of the fabricated EDLCs. Amount of activated charcoal and natural graphite plays a noticeable role on the capacity. 50 graphite : 40 AC : 10 PVdF showed the optimum single electrode specific capacity value of 15 F/g. Capacity is determined by the cycling rate as well as the potential window within which cycling is being done. Continuous cycling resulted an average single electrode specific capacity variation of 48 F/g - 16 F/g. Capacity fading was higher at the beginning. Later, it dropped noticeably. Initial discharge capacity drop under Galvanostatic Charge Discharge test was slightly fast but reached near stable upon continuous charge discharge process. It can be concluded that initially some agitation is required to reach the maturity. However, the results can be considered as encouraging to initiate studies on EDLCs using Sri Lankan natural graphite.

• 폴리머
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• 제26권2호
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• pp.179-184
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• 2002

양성자 전도도가 높으며 균일하고 또 기계적 강도가 우수한 양성자 전도체를 얻기 위하여 poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) 공중합체를 전해질의 지지체로 선택하고, $H_3PO_4$이 포함된 ethylene carbonate (EC)와 $\gamma$-butyrolactone (BL) 및 dimethyl carbonate (DMC)의 유기용매들을 혼합하여 겔-전해질을 제조하였다. 다양한 조성의 겔-전해질에 대하여 열분석과 전도도 측정 실험을 수행하였다. 상온에서 양성자 전도도는 30(PVdF-HFP) + 50EC/DMC + $20H_3PO_4$ 전해질에서 7.3$\times$$10^{-3}Sm^{-1}$/로 가장 높았다. 열분석 결과에서 거의 모든 시료는 대략 $80^{\circ}C$ 정도까지 안정하였으며, 특히 인산은 고분자 사슬과 민감하게 반응하여 고분자와 용매의 혼화성을 증대시키는 것을 확인하였다.

• 전기화학회지
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• 제10권3호
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• pp.213-218
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• 2007

리튬/유황 전지에 적합한 전해질을 조사하기 위하여, 여러 종류의 글라임(glyme)계 가소제를 넣은 폴리비닐리덴플로라이드(poly(vinylidene fluoride):PVdF) 겔 고분자 전해질을 제조하여 전기화학적 특성을 실험하였다. 가소제는 에틸렌옥사이드(ethylene oxide; EO) 구조를 가지는 glyme계 유기용매 중에서, EO의 체인 길이가 다른 트리글라임(triglyme), 테트라글라임(tetraglyme), 폴리글라임(polyglyme (Mn=250, 500))의 네 종류를 사용하였다. 가소제 내의 EO의 체인 길이가 길어질수록 PVdF 겔 고분자 전해질의 이온전도도는 감소하였다. PVdF 겔 고분자 전해질의 가소제로 triglyme을 사용한 경우의 이온전도도가 $5.38{\times}10^{-4}\;S/cm$로 가장 높았으며, polyglyme(Mn=500)를 사용한 경우에는 $2.80{\times}10^{-4}\;S/cm$으로 가장 낮았다. 그러나 계면저항은 tetraglyme을 사용한 경우에 가장 낮게 나타났으며, 이 전해질을 리튬/유황 전지에 적용하였을 때 1232 mAh/g-S(이론용량의 70%)의 높은 초기 방전 용량을 나타내었다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.65-66
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• 2006

[ $TiO_2$ ] single crystalline nanorods are prepared from electrospun fibers which are composed of nanofibrils with an island-in-a-sea morphology. The mechanical pressure produces each fibril into nanorods which are converted to anatase single crystals after calcinations. HRTEM shows that the (001) plane is growing along the longitudinal direction of the rod. In this work, the nanorod electrode provides the efficient photocurrent generation in a quasi-solid state dye-sensitized solar cells (DSSCs) using highly viscous PVDF-HFP based gel electrolytes. The overall converision efficiency of the $TiO_2$ nanorods shows 6.2 % under $100\;mW/cm^2$ (AM 1.5G) illumination.

• 전기화학회지
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• 제14권2호
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• pp.117-124
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• 2011

We demonstrate a new surface modification of high-voltage lithium cobalt oxide ($LiCoO_2$) cathode active materials for lithium-ion batteries. This approach is based on exploitation of a polarity-tuned gel polymer electrolyte (GPE) coating. Herein, two contrast polymers having different polarity are chosen: polyimide (PI) synthesized from thermally curing 4-component (pyromellitic dianhydride/biphenyl dianhydride/phenylenediamine/oxydianiline) polyamic acid (as a polar GPE) and ethylene-vinyl acetate copolymer (EVA) containing 12 wt% vinyl acetate repeating unit (as a less polar GPE). The strong affinity of polyamic acid for $LiCoO_2$ allows the resulting PI coating layer to present a highly-continuous surface film of nanometer thickness. On the other hand, the less polar EVA coating layer is poorly deposited onto the $LiCoO_2$, resulting in a locally agglomerated morphology with relatively high thickness. Based on the characterization of GPE coating layers, their structural difference on the electrochemical performance and thermal stability of high-voltage (herein, 4.4 V) $LiCoO_2$ is thoroughly investigated. In comparison to the EVA coating layer, the PI coating layer is effective in preventing the direct exposure of $LiCoO_2$ to liquid electrolyte, which thus plays a viable role in improving the high-voltage cell performance and mitigating the interfacial exothermic reaction between the charged $LiCoO_2$ and liquid electrolytes.

• 전기화학회지
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• 제3권3호
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• pp.169-172
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• 2000

Polyacrylonitrile (PAN) 고분자의 유기용매 함유능을 증대시키기 위하여 PAN을 수정한 새로운 polyacrylonitrile-co-bis[2-(2-methoxyethoxy)ethyl]itaconate (PANI로 약칭) 공중합체를 합성하였다. PAN과 PANI의 혼합 고분자에 ethylene carbonate (EC)와 dimethyl carbonate (DMC)의 혼합유기용매, $LiClO_4$ 염을 혼합한 젤 고분자 전해질을 제조하였다. 상온에서의 이온전도도는 25PAN +10PANl +50EC/DMC+$15LiClO_4$ 조성의 전해질에서 $2\times10^{-3}\; Scm^{-1}$로 가장 높은 값을 나타내었다. 이는 PANI의 혼합으로 인하여 유기용매 영역의 결정질 성분이 줄어들고, 따라서 전하운반자의 수가 증가하기 때문인 것으로 분석하였다. PANI를 고분자 기질로 적당량 첨가하면, PAN만을 단용으로 사용한 젤-전해질에 비해 기계적 강도가 감소하는 단점이 있기는 하지만, 이온전도성, 열적 특성, 용매와의 혼화성, 전기화학적 안정성, 리튬 전극과의 계면 안정성 등 거의 모든 면에서 성능이 개선되는 것으로 나타났다.

• 전기화학회지
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• 제4권1호
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• pp.6-9
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• 2001

유리섬유(glass fiber cloth, GFC)가 보강제로 사용된 고분자 겔 전해질(polymeric gel electrolytes, PGEs)에 $SiO_2$를 첨가하여 전해질의 전기 화학적 특성을 조사하였다. 가소제로는 Ethylene carbonate(EC) , propylene carbonate(PC), diethyl carbonate(DEC)를, 리튬염으로는 $LiClO_4$를 고분자로는 polyacrylronitrile(PAN)과 poly(vinylidene fluoride-co-hexafluoro propylene)(P(VdF-co-HFP))을 사용하여 $80\~90{\mu}m$의 두께로 전해질을 제조하였다. 제조된 전해질은 모두 상온체서 $10^{-3}S/cm$의 이온 전도도를 나타내었고, 4.8V까지 안정하였다. 리튬금속을 사용하여 제조된 셀의 임피던스 결과에서는 시간이 지남에 따라 모든 전해질이 부동태 피막의 성장으로 계면저항이 증가했으나, $SiO_2$첨가비율에 따라 뚜렷한 차이는 보이지 않았다. $LiClO_2$와 mesophase pitch-based carbon fiber(MCF)를 각각 양극과 음극으로 사용하여 제조된 겔의 임피던스에서는 $SiO_2$가 첨가되지 않은 셀의 옴 저항이 충전, 방전이 진행되는 동안 많은 변화를 보였으며, $SiO_2$가 첨가된 셀의 저항은 거의 변화되지 않았고, 계면의 변화도 적었다. 또한 방전용량에서도 $SiO_2$가 $20\%$가 첨가된 전해질이 0.2C의 방전속도에132mAh/g의 비 용량을 나타내었고, 2C의 방전속도에서$85\%$의 방전용량을 유지하였다.

• 전기화학회지
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• 제14권2호
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• pp.83-91
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• 2011

Mesoporous titanium dioxide ($TiO_2$) thin films were prepared using poly(vinyl chloride)-graft-poly(N-vinyl pyrrolidone) (PVC-g-PVP) as a templating agent via sol-gel process. Grafting of PVC chains from PVC backbone was done by atom transfer radical polymerization (ATRP) technique. The successful grafting of PVP to synthesize PVC-g-PVP was checked by fourier-transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The carbonyl group interaction of PVC-g-PVP graft copolymer with $TiO_2$ was confirmed by FT-IR. The porous morphologies of the $TiO_2$ films genereated after calcination at $450^{\circ}C$ was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mesoporous $TiO_2$ films with 580 nm in thickness were used as a photoelectrode for solid state dye sensitized solar cell (DSSC) and showed an energy conversion efficiency of 1.05% at 100 $mW/cm^2$.

• 한국표면공학회지
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• 제28권1호
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• pp.46-54
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• 1995

An electrochromic(EC) cell was constructed using $WO_3$ as a electrochromic material and NiO as a counter electrode, deposited onto ITO-coated glass by the implementation of electron beam evaporation. The electrolytic media were both lithium and proton conducting polymers such as poly-acrylonitrile(PAN)-$LiClO_4$, poly-ethylene oxide(PEO)-$LiClO_4$, poly-vinyl butyral(PVB)-LiCl and PVB-H$_3$$PO_4$. Potentiodynamic cycling of the cells using PAN-$LiClO_4$, or PVB-$H_3$$PO_4$ electrolyte yielded a transmission variation of more than 40% at the wavelength of 632.8 nm within less than 10 sec response time at room temperature. These results indicate that these electrolytes, transparent in gel type, are premising for the application in large area electrochromic windows.