• Title/Summary/Keyword: Gel-Polymer Electrolyte

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Polarity-tuned Gel Polymer Electrolyte Coating of High-voltage LiCoO2 Cathode Materials

  • Park, Jang-Hoon;Cho, Ju-Hyun;Kim, Jong-Su;Shim, Eun-Gi;Lee, Yun-Sung;Lee, Sang-Young
    • Journal of the Korean Electrochemical Society
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    • v.14 no.2
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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.

Effect of Monomers and Initiators on Electrochemical Properties of Gel Polymer Electrolytes (젤 고분자 전해질의 전기화학적 특성에 대한 단량체 및 개시제의 영향)

  • Park, Hyoun-Gyu;Ryu, Sang-Woog
    • Polymer(Korea)
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    • v.34 no.4
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    • pp.357-362
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    • 2010
  • Poly(ethyleneglycol diacrylate)(PEGDA) or 2-ethylhexyl acrylate(2EHA)-based gel polymer electrolytes(GPEs) which have a solid content in the range of 8~54 wt% were synthesized and their ionic conductivity and electrochemical properties were measured at room temperature. It was observed that the ionic conductivity over $1\times10^{-3}$ S/cm was obtained in a homogeneous PEGDA-based GPE with 21 wt% of solid content. However the electrochemical stability of the GPE was lower than that of a liquid electrolyte. The presence of AIBN initiator which can produce a N2 gas during polymerization process might be the reason of this low oxidation decomposition potential. As an alternative, benzoyl peroxide was used as an initiator and GPE with enhanced electrochemical stability was obtained. Finally, the formation of stable solid electrolyte interphase on a graphite anode was evidenced by cyclic voltammetry measurement.

Preparation of UV Curable Gel Polymer Electrolytes and Their Electrochemical Properties

  • Oh, Boo-Keun;Jung, Won-Il;Kim, Dong-Won;Rhee, Hee-Woo
    • Bulletin of the Korean Chemical Society
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    • v.23 no.5
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    • pp.683-687
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    • 2002
  • We have investigated the effect of the number of ethylene oxide (EO) units inside poly(ethylene glycol)dimethacrylate (PEGDMA) on the ionic conductivity of its gelled polymer electrolyte, whose content ranges from 50 to 80 wt%. PEGDMA gelled polym er electrolytes, a crosslinked structure, were prepared using simple photo-induced radical polymerization by ultraviolet light. The effect of the number of EO on the ionic conductivity was clearly shown in samples of lower liquid electrolyte content. We have concluded that the ionic conductivity increased in proportion to both the number of EO units and the plasticizer content. We have also studied the electrochemical properties of 13PEGDMA (number of EO units is 13) gelled polymer electrolyte.

Effect of Plasticizer on Electrolyte Membranes for Dye Sensitized Solar Cells (염료감응형 태양전지를 위한 고분자 전해질막에서의 가소제의 효과)

  • Cho, Doo-Hyun;Jung, Yoo-Young;Yun, Mi-Hye;Kwon, So-Young;Koo, Ja-Kyung
    • Membrane Journal
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    • v.20 no.1
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    • pp.13-20
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    • 2010
  • Using poly(ethylene oxide) (PEO) as a polymer host, poly(ethylene glycol) (PEG) as a plasticizer, potassium iodide and iodine as sources of $I^-/{I_3}^-$ PEO-PEG-KI/$I_2$ polymer gel electrolytes were prepared. Based on the polymer gel electrolytes, solid-state dye-sensitized solar cell(DSSC)s were fabricated. The content of PEG in the electrolyte was changed from 0 to 85%. The electrolyte showed self-supporting form through whole range of the PEG content. As the PEG content increased, the ionic conductivity and ${I_3}^-$ diffusivity increased and the light-to electrical energy conversion efficiency increased under irradiation of 100 $mWcm^{-2}$ simulated sunlight.

Thermal and Electrical Properties of Poly(vinylidene fluoride-hexafluoropropylener)-Based Proton Conducting Gel-Electrolytes (Poly(vinylidene fluoride-hexafluoropropylene)계 양성자 전도성 겔-전해질의 열적, 전기적 특성)

  • 최병구;박상희
    • Polymer(Korea)
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    • v.26 no.2
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    • pp.179-184
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    • 2002
  • Polymer electrolyte films consisting of poly (vinylidenefluoride-hexafluoro-propylene) (PVdF-HFP) $H_3PO_4$and a mixture of ethylene carbonate(EC), $\gamma$-butyrolactone(BL) and dimethylcarbonate (DMC) were examined in order to obtain the best compromise between high protonic conductivity, homogeniety and dimensional stability. Measurements of differential scanning calorimetry and ionic conductivity have been carried out for various compositions. The highest proton conductivity of 7.3 $\times$$10^{-3}Sm^{-1}$ at $30^{\circ}C$ were obtained for a film of 30(PVdF-HFP) + 50EC/DMC + 20H$_3$PO$_4$. From the thermal study, it has been found that the PVdF-HFP gels are stable up to $80^{\circ}C$, and the $H_3PO_4$ enhances the miscibility of the polymer and the solvent by interacting sensitively with polymer segments.

Improving Power Conversion Efficiency and Long-term Stability Using a Multifunctional Network Polymer Membrane Electrolyte; A Novel Quasi-solid State Dye-sensitized Solar Cell

  • Gang, Gyeong-Ho;Gwon, Yeong-Su;Song, In-Yeong;Park, Seong-Hae;Park, Tae-Ho
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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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.

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Characterization of a New Poly(acrylonitrile-itaconate) based Gel-electrolyte (새로운 poly(acrylonitrile-itaconate)공중합체를 기초로 한 젤-전해질의 특성)

  • Choi B. K.;Kim S. H.;Gong M. S.
    • Journal of the Korean Electrochemical Society
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    • v.3 no.3
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    • pp.169-172
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    • 2000
  • A new gel polymer electrolyte based on the modified polyacrylonitrile (PAN), polyacrylonitrile-co-bis[2-(2-methoxyethoxy)ethyl]itaconate (abbreviated as PANI) copolymer was synthesized in expectation of enhanced trapping ability of liquid electrolytes. PAN and PANI blend was complexed with organic solvents, ethylene carbonate (EC) and dimethyl carbonate (DMC), and $LiClO_4$ salt. The highest room temperature conductivity of $2\times10^{-3}\;Scm^{-1}$ was found for a film of 25PAN+10PANl+50EC/DMC+$15LiClO_4$. The solvent-rich crystalline part decreases due to the blending of PANI and therefore number of charge carriers increases giving higher ionic conductivity. The addition of PAM as a host polymer in the PAN-based gels has beneficial effects such as higher ionic conductivity, better thermal characteristics, better miscibility with solvent, wider electrochemical stability, and better interfacial stability with lithium electrode, though it exhibits slightly less mechanical rigidity.