• Membrane Journal
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• v.27 no.4
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• pp.358-366
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• 2017

The most important factor in the performances of polymer electrolyte membranes for fuel cells is how fast hydrogen ions can be transported along the water channel formed inside the electrolyte membrane. Since the morphology of the water channel and the diffusivity of the protons are very important factors for the proton transport behavior, various molecular dynamics simulation studies are being carried out to clarify this. The force-field is an important variable parameterizing the movement and interaction of each atom in molecular dynamics simulation. In this study, proton diffusivities of the 3D models of polymer electrolyte membranes were calculated in order to analyze the effects of various types of force-fields on the molecular simulation. It has been found that the charge value determining the non-bonding interaction plays a very important role in the formation of the water channel morphology, and the COMPASS force-field can calculate the accurate proton diffusion behavior. Accordingly, for molecular dynamics simulation of polymer electrolyte membranes, the proper selection of the force-field is very important due to its great effect on the proton diffusion as well as the final molecular structure.

• Polymer(Korea)
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• v.35 no.2
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• pp.106-112
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• 2011

Aromatic copolyamides were prepared and their applicability to proton exchange membrane was studied. The copolymers contain two segments; thermally stable and mechanically strong poly (p-phenylene terephthalamide) (PPTA), and easily processable and good film-forming polysulfone. For the copolymers, different ratios of amine-terminated sulfonated ether sulfone monomer, terephthaloyl chloride, and p-phenylene diamine were sequentially reacted. The obtained copolymers were mixed with trimethylolpropane triglycidyl ether (TMPTGE), thermally cured, and converted into proton exchange membranes for fuel cell application. The reactions at each step and the molecular characteristics of precursor copolymers were confirmed by $^1H$ NMR, FTIR, and titration. The performance of the membranes was measured in terms of water uptake and proton conductivity. The water uptake, ion exchange capacity (IEC), and proton conductivity of the membranes increased with the increase of sulfonated ether sulfone segment content. Membrane containing 60 mol% sulfonic acid sulfone segment showed 1.88 meq/g IEC value. Water uptake was limited less than 110 wt% and the highest proton conductivity was up to $7.4{\times}10^{-2}$ S/cm ($25^{\circ}C$, RH=100%).

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.203-218
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• 2009

The development of lithium-ion battery (LIB) technologies and their application in the field of large-scale power sources, such as electric vehicles (EVs), hybrid EVs, and plug-in EVs require enhanced reliability and superior safety. The main components of LIBs should withstand to the inevitable heating of batteries during high current flow. Carbonate solvents that contribute to the dissociation of lithium salts are volatile and potentially combustible and can lead to the thermal runaway of batteries at any abuse conditions. Recently, an interest in nonflammable materials is greatly growing as a means for improving battery safety. In this review paper, novel approaches are described for designing highly safe electrolytes in detail. Non-flammability of liquid electrolytes and battery safety can be achieved by replacing flammable organic solvents with thermally resistive materials such as flame-retardants, fluorinated organic solvents, and ionic liquids.

• Polymer(Korea)
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• v.31 no.4
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• pp.297-301
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• 2007

In this work, polymer/(layered silicate) nanocomposites (PLSN) based on poly (ethylene oxide) (PEO), ethylene carbonate (EC) as a plasticizer, lithium salt ($LiClO_4$), and sodium montmorillonite ($Na^+-MMT$) or organic montmorillonite (organic MMT) clay were fabricated. And the effects of organic MMT on the polymer matrix were investigated as a function of ionic conductivity. For the application to electrolytes an Li batteries, polymer electrolytes containing the organic nanoclays were used in this work. As a result, the spacing between layers and hydrophobicity of the organic nanoclays were increased, affecting on the exfoliation behaviors of the MMT layers in clay/PEO nanocomposites. From ion-conductivity results, the organic-MMT showed higher values than those of $Na^+-MMT$, and the MMT-20A sample that was treated by methyl dihydrogenated tallow ammonium, showed the highest conductivity in this system.

• Journal of the Korean Electrochemical Society
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• v.16 no.4
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• pp.198-203
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• 2013

Copolymer consisted of MMA and tBMA was synthesized by radical polymerization and poly(MMA-co-MA) was prepared by selective hydrolysis of tert-butyl group. The obtained polymer was coupled with epoxy functionalized PEO of various molecular weight to synthesize poly(MMA-co-PEGMA) with different side chain length. The AC-impedance measurement shows $1.88{\times}10^{-6}Scm^{-1}$ of room temperature ionic conductivity from 48mol% of MMA while $5.11{\times}10^{-8}Scm^{-1}$ was observed in 82mol% sample. In addition, there was an effect of PEGMA molecular weight on ionic conductivity possibly due to the steric hindrance in grafting-onto coupling reaction. Finally, the polymer electrolytes shows electrochemical stability up to 6V at room temperature.

• Journal of the Korean Electrochemical Society
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• v.26 no.4
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• pp.71-79
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• 2023

In this study, we employed anionic, cationic, and nonionic surfactants for the hydrophilization of porous substrates used in the fabrication of pore-filling membranes. We investigated the extent of hydrophilization based on the type of surfactant, its concentration, and immersion time. Furthermore, we used the hydrophilized substrates to produce pore-filling anion exchange membranes and compared their ion conductivity to determine the optimal hydrophilization conditions. For the ionic surfactants used in this study, we observed that hydrophilization progressed rapidly from the beginning of immersion when the applied concentration was 3.0 wt%, compared to lower concentrations (0.05, 0.5, and 1.0 wt%). In contrast, for the relatively larger molecular weight non-ionic surfactants, smooth hydrophilization was not observed. There was no apparent correlation between the degree of hydrophilization and the ion conductivity of the anion exchange membrane. This discrepancy suggests that an excessive hydrophilization process during the treatment of porous substrates leads to excessive adsorption of the surfactant on the sparse surfaces of the porous substrate, resulting in a significant reduction in porosity and subsequently decreasing the content of polymer electrolyte capable of ion exchange, thereby greatly increasing the electrical resistance of the membrane.

• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.87-103
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• 2019

Nonaqueous organic electrolyte solution in commercially available lithium-ion batteries, due to its flammability, corrosiveness, high volatility, and thermal instability, is demanding to be substituted by safer solid electrolyte with higher cycle stability, which will be utilized effectively in large-scale power sources such as electric vehicles and energy storage system. Of various types of solid electrolytes, composite solid electrolytes with polymer matrix and active inorganic fillers are now most promising in achieving higher ionic conductivity and excellent interface contact. In this review, some kinds and brief history of solid electrolyte are at first introduced and consequent explanations of polymer solid electrolytes and inorganic solid electrolytes (including active and inactive fillers) are comprehensively carried out. Composite solid electrolytes including these polymer and inorganic materials are also described with their electrochemical properties in terms of filler shapes, such as particle (0D), fiber (1D), plane (2D), and solid body (3D). In particular, in all-solid-state lithium batteries using lithium metal anode, the interface characteristics are discussed in terms of cathode-electrolyte interface, anode-electrolyte interface, and interparticle interface. Finally, current requisites and future perspectives for the composite solid electrolytes are suggested by help of some decent reviews recently reported.

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.289-295
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• 2022

In this study, we intend to fabricate an all solid polymer battery with a reduced interfacial resistance between the solid electrolyte and the electrode by applying thiophene based polymers as both electrode and electrolyte materials. In order to minimize the interfacial resistance with the poly(3,4-ethylenedioxy thiophene) (PEDOT) based electrode, 3,4-ethylenedioxy thiophene (EDOT) oligomer was introduced into the solid electrolyte. Also, to improve the lithium salt dissociation ability of the EDOT oligomer [oligo(EDOT)] electrolyte, it was blended with poly(vinylidene fluoride) (PVdF). As a result, the ionic conductivity of the solid polymer electrolyte increased by introducing PVdF into the oligo (EDOT). From the result of evaluating the electrochemical properties of an all solid polymer battery, the interfacial resistance significantly decreased by introducing a thiophene based polymer to the electrode and electrolyte.

• Journal of the Korean Electrochemical Society
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• v.13 no.3
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• pp.181-185
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• 2010

Polyaniline-ionic liquid composite was prepared and investigated its physical and electrochemical properties. The quasi-solidification was presented in imidazolium-based ionic liquid (1-methly-3-propylimidazolium iodide, PMI-I) containing above 30 wt% of polyaniline (emeraldine base), which exhibited around 80% decrease of conductivity compared to pristine ionic liquid, resulting in fibril structure trough ${\pi}-{\pi}$ self-assembled of imidazolium aromatic ring of ionic liquid on polyaniline framework.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.758-763
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• 2011

In this work, polymer composite electrolytes were prepared by a blend of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) as a polymer matrix, propylene carbonate as a plasticizer, $LiClO_4$ as a salt, and by containing a different content of $TiO_2$, by using the solution casting method. The crystallinity and ionic conductivity of the polymer electrolytes was evaluated using X-ray diffraction(XRD) and AC impedance method, respectively. The morphology of composite electrolyte film was analyzed by SEM method. From the experimental results, by increasing the $TiO_2$ content, crystallinity of PEO was reduced, and ionic conductivity was increased. In particular, the ionic conductivity was dependent on the content of $TiO_2$ and showed the highest value 15 wt%. However, when $TiO_2$ content exceeds 15 wt%, the ionic conductivity was decreased. According to the surface morphology, the ionic conductivity was decreased because the polymer composite electrolytes showed a heterogenous morphology of fillers due to immiscibility or aggregation of the filler within the polymer matrix.