• Macromolecular Research
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• 제16권5호
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• pp.424-428
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• 2008

We prepared an ionic gel polymer electrolyte for dye-sensitized solar cells (DSSCs) without leakage problem. Triiodide compound (BTDI) was synthesized by the reaction of benzene tricarbonyl trichloride with diethylene glycol monotosylate and subsequent substitution of tosylate by iodide using NaI. Bisimidazole was prepared by the reaction of imidazole with the triethylene glycol ditosylate under strongly basic condition provided by NaH. BTDI and bisimidazole dissolved in an ionic liquid were injected into the cells and permeated into the $TiO_2$ nanopores. In situ crosslinking was then carried out by heating to form a network structure of poly(imidazolium iodide), thereby converting the ionic liquid electrolytes to a gel or a quasi-solid state. A monomer (BTDI and bisimidazole) concentration in the electrolytes of as low as 30 wt% was sufficient to form a stable gel type electrolyte. The DSSCs based on the gel polymer electrolytes showed a power conversion efficiency of as high as 1.15% with a short circuit current density of $5.69\;mAcm^{-2}$, an open circuit voltage of 0.525 V, and a fill factor of 0.43.

• Korean Membrane Journal
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• 제4권1호
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• pp.36-40
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• 2002

The diffusion coefficients of ions in the reverse transport system using the carrier mediated membrane were estimated from the diffusional membrane permeabilities and the ion activity in membrane system. In the aqueous alkali metal ions-membrane system diffusional flux of alkali metal ions driven by coupled proton was analyzed. The aqueous phase I contained NaOH solution and the aqueous phase II also contained NaCl and HCl mixed solution. The concentration of Na ions of both phases were $10^{0},\;10^{-1},\;10^{-2},\;5{\times}10^{-1}\;and\;5{\times}10^{-2}\;mol{\cdot}dm^{-3}$ and the concentration of HCI in aqueous phase II was always kept at $1{\times}10^{-1}\;mol{\cdot}dm^{-3}$. Moreover, the carrier concentration in liquid membrane was $10^{-2}\;mol{\cdot}dm^{-3}$. The results indicated that the diffusion coefficients depend strongly on the concentration of both phases electrolyte solution equilibriated with the membrane. The points were interpreted in terms of the energy barrier theory. Furthermore, eliminating the potential terms from the membrane equation was derived.

• 전기화학회지
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• 제18권2호
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• pp.51-57
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• 2015

상온 이온성 액체인 propylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMPyr-TFSI)를 리튬이차전지 전해질 용매로 사용 시 PMPyr-TFSI 내 수분 및 브롬 불순물이 전지의 성능에 미치는 영향을 연구하였다. 고전압 양극 물질인 $LiNi_{0.5}Mn_{1.5}O_4$ 스피넬 구조 양극을 이용한 반쪽 전지의 전해질로 PMPyr-TFSI를 사용 하는데 있어, PMPyr-TFSI의 수분 함유량을 각각 12, 77, 1060 ppm으로 제어하고 전압 곡선 개형 및 쿨롱 효율 거동 추적을 통해 PMPyr-TFSI 수분량이 전지 성능에 부정적인 영향을 미치는 것을 구체적으로 확인하였다. 또한, PMPyr-TFSI 전해질 내의 브롬 이온 불순물 양 제어를 통하여, 전지 내에서 브롬 이온 불순물과 관련한 전기화학 부반응을 찾아 내었다. 이들 할로겐 불순물에 의한 초기 전지 쿨롱 효율저하는 눈에 띠었으나, 수명 저하에는 큰 변화가 없음을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제29권1호
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• pp.41-55
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• 2018

General polymer electrolyte fuel cell (PEMFC) operates at less than $80^{\circ}C$. Therefore liquid phase water resulting from electrochemical reaction accumulates and floods the cell which in turn increases the mass transfer loss. To prevent the flooding, it is common to employ serpentine flow channel, which can efficiently export liquid phase water to the outlet. The major drawback of utilizing serpentine flow channel is the large pressure drop that happens between the inlet and outlet. On the other hand, in the high temperature polymer electrolyte fuel cell (HT-PEMFC), since the operating temperature is 130 to $180^{\circ}C$, the generated water is in the state of gas, so the flooding phenomenon is not taken into consideration. In HT-PEMFCs parallel flow channel with lower pressure drop between the inlet and outlet is employed therefore, in order to circulate hydrogen and air in the cell less pumping power is required. In this study we analyzed HT-PEMFC's different flow channels by parallel computation using previously developed 3-D isothermal model. All the flow channels had an active area of $25cm^2$. Also, we numerically compared the performance of HT-PEMFC parallel flow channel with different manifold area and Rib interval against the original serpentine flow channel. Results of the analysis are shown in the form of three-dimensional contour polarization curves, flow characteristics in the channel, current density distribution in the Membrane, overpotential distribution in the catalyst layer, and hydrogen and oxygen concentration distribution. As a result, the performance of a real area fuel cell was predicted.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.484.2-484.2
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• 2014

There are many efforts to improving the power conversion efficiencies (PCEs) of dye-sensitized solar cells (DSCs). Although DSCs have a low production cost, their low PCE and low thermal stability have limited commercial applications. This study describes the preparation of a novel multifunctional polymer gel electrolyte in which a cross-linking polymerization reaction is used to encapsulate $TiO_2$ nanoparticles toward improving the power conversion efficiency and long-term stability of a quasi-solid state DSC. A series of liquid junction dye-sensitized solar cells (DSCs) was fabricated based on polymer membrane encapsulated dye-sensitized $TiO_2$ nanoparticles, prepared using a surface-induced cross-linking polymerization reaction, to investigate the dependence of the solar cell performance on the encapsulating membrane layer thickness. The ion conductivity decreased as the membrane thickness increased; however, the long term-stability of the devices improved with increasing membrane thickness. Nanoparticles encapsulated in a thick membrane (ca. 37 nm), obtained using a 90 min polymerization time, exhibited excellent pore filling among $TiO_2$ particles. This nanoparticle layer was used to fabricate a thin-layered, quasi-solid state DSC. The thick membrane prevented short-circuit paths from forming between the counter and the $TiO_2$ electrode, thereby reducing the minimum necessary electrode separation distance. The quasi-solid state DSC yielded a high power conversion efficiency (7.6/8.1%) and excellent stability during heating at $65^{\circ}C$ over 30 days. These performance characteristics were superior to those obtained from a conventional DSC (7.5/3.5%) prepared using a $TiO_2$ active layer with the same thickness. The reduced electrode separation distance shortened the charge transport pathways, which compensated for the reduced ion conductivity in the polymer gel electrolyte. Excellent pore filling on the $TiO_2$ particles minimized the exposure of the dye to the liquid and reduced dye detachment.

• Bulletin of the Korean Chemical Society
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• 제29권9호
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• pp.1705-1710
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• 2008

Imidazolium based zwitterions, 1,2-dimethylimidazolium-3-n-propanesulfonate (DMIm-3S) and 1-Butylimidazolium-3-n-butanesulphonate (BIm-4S), were synthesized, and utilized them as additive for Li ion cell comprising of graphite anode and $LiCoO_2$ cathode. The use of 10 wt% of DMIm-3S in 1 M $LiPF_6$, EC-EMCDMC (1:1:1 (v/v)) resulted in the increased high rate charge-discharge performance. The low temperature performance of the Li ion cells at about −20 ${^{\circ}C}$ was also enhanced by these zwitterion additives. The DMIm- 3S additive resulted in the better capacity retention by the Li-ion cells even after 120 cycles with 100% depth of discharge (DOD) at 1 C rate in room temperature. Surface morphology of both graphite and $LiCoO_2$ electrode before and after 300 cycles was studied by scanning electron microscopy. An analogous study was performed using liquid electrolyte without any additive.

• 한국재료학회지
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• 제31권11호
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• pp.614-618
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• 2021

As the size of market for electric vehicles and energy storage systems grows, the demand for lithium-ion batteries (LIBs) is increasing. Currently, commercial LIBs are fabricated with liquid electrolytes, which have some safety issues such as low chemical stability, which can cause ignition of fire. As a substitute for liquid electrolytes, solid electrolytes are now being extensively studied. However, solid electrolytes have disadvantages of low ionic conductivity and high resistance at interface between electrode and electrolyte. In this study, Li₇La₃Zr₂O₁₂ (LLZO), one of the best ion conducting materials among oxide based solid electrolytes, is fabricated through RF-sputtering and various electrochemical properties are analyzed. Moreover, the electrochemical properties of LLZO are found to significantly improve with co-sputtered Li₂O. An all-solid thin film battery is fabricated by introducing a thin film solid electrolyte and an Li₄Ti₅O₁₂ (LTO) cathode; resulting electrochemical properties are also analyzed. The LLZO/Li₂O (60W) sample shows a very good performance in ionic conductivity of 7.3×10^-8 S/cm, with improvement in c-rate and stable cycle performance.

• 전기화학회지
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• 제5권4호
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• pp.216-220
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• 2002

The effects of electrolytes on electrochemical behavior from an oil thin layer interposed between a graphite electrode and an aqueous solution phase were examined. A hydrophobic electroactive species, tetrachloro-1,4-benzoquinone (TCQ), in a benzonitrile (EN) layer was employed to study ion transfer properties across the BN-water interface. Experimental results showed that hydrophobic cations as well as anions could be successfully used as ionic charge carriers. The addition of various salts into either the oil layers or the aqueous solutions offers deeper insight for the electrochemistry of the liquid thin layer system. When aqueous perchloric acid is interfaced with the BN films, the perchlorate ion of tetrahexylammonium perchlorate (THAP) substantially suppresses the dissociated proton concentration in the layer by the common ion effect while there is only a little change in the total acid concentration. Further approach by theoretical calculation makes it possible to quantitatively understand the effect of the electrolytes to the electrochemical responses of TCQ, which were previously reported (Anal. Chem. 73, 337 (2001)).

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.42-47
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• 2024

The electrochemical extraction of uranium in ternary low melting LiCl-KCl-CsCl eutectic on inert and reactive electrodes via different electrochemical techniques was investigated. It was established that the electrochemical reduction process of U(III) ions on the inert W electrode was irreversible and proceeded in one stage. On reactive liquid Ga and liquid Cd electrodes the reduction of uranium ions took place with the considerable depolarization with the formation of UGa₂, UGa₃ and UCd₁₁ intermetallic compounds. Thermodynamic characteristics of uranium compounds and alloys were calculated. The conditions for the extraction of uranium from the electrolyte in the form of alloys on both liquid reactive electrodes via potentiostatic electrolysis were found.

• Korean Chemical Engineering Research
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• 제53권5호
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• pp.638-645
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• 2015

Vanadium redox flow batteries (VRFBs) have been investigated for their potential utility as large energy storage systems due to their advantageous performances in terms of long cycle life, high energy efficiency, low cost, and flexible design. Carbon materials are typically used as electrodes in redox reactions and as a liquid electrolyte support. The activities, surface areas, and surface morphologies of porous carbon materials must be optimized to increase the redox flow battery performance. Here, to reduce the resistance in VRFBs, surface-modified carbon felt electrodes were fabricated, and their structural, morphological, and chemical properties were characterized. The surface-modified carbon felt electrode improved the cycling energy efficiencies in the VRFBs, from 65% to 73%, due to the improved wettability with electrolyte. From the results of impedances analysis with proposed fitting model, the electrolyte-coupled polarization in VRFB dramatically decreased upon modification of carbon felt electrode surface. It is also demonstrated that the compressibility of carbon felt electrodes was important to the VRFB polarization, which are concerned with mass transfer polarization. The impedance analysis will be helpful for obtaining better and longer-lived VRFB performances.