• Journal of Powder Materials
• /
• v.31 no.1
• /
• pp.23-29
• /
• 2024

This study investigates the effect of the microstructure of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), a solid electrolyte, on its ionic conductivity. Solid electrolytes, a key component in electrochemical energy storage devices such as batteries, differ from traditional liquid electrolytes by utilizing solid-state ionic conductors. LATP, characterized by its NASICON structure, facilitates rapid lithium-ion movement and exhibits relatively high ionic conductivity, chemical stability, and good electrochemical compatibility. In this study, the microstructure and ionic conductivity of LATP specimens sintered at 850, 900, and 950℃ for various sintering times are analyzed. The results indicate that the changes in the microstructure due to sintering temperature and time significantly affect ionic conductivity. Notably, the specimens sintered at 900℃ for 30 min exhibit high ionic conductivity. This study presents a method to optimize the ionic conductivity of LATP. Additionally, it underscores the need for a deeper understanding of the Li-ion diffusion mechanism and quantitative microstructure analysis.

• Journal of Forest and Environmental Science
• /
• v.36 no.2
• /
• pp.69-77
• /
• 2020

Lignocellulosic biomass has recalcitrant characteristics against chemical and biological conversion due to its structural heterogeneity and complexity. The pretreatment process to overcome these recalcitrant properties is essential, especially for the biochemical conversion of lignocellulosic biomass. In recent years, pretreatment methods using ionic liquids (ILs) and deep eutectic solvents (DESs) as the green solvent has attracted great attention because of their advantages such as easy recovery, chemical stability, temperature stability, nonflammability, low vapor pressure, and wide liquids range. However, there are some limitations such as high viscosity, poor economical feasibility, etc. to be solved for practical use. This paper reviewed the research activities on the pretreatment effect of various ILs including DESs and their co-solvents with organic solvents on the enzymatic saccharification efficiency of lignocellulosic biomass and the nanocellulose preparation from the pretreated products.

• Journal of Electrochemical Science and Technology
• /
• v.1 no.1
• /
• pp.57-62
• /
• 2010

The lithium ion concentration dependant ionic conductivity and thermal properties of poly(ethylene glycol) methyl ether methacrylate (PEGMA)/acrylonitrile-based copolymer electrolytes with $LiClO_4$ have been studied by differential scanning calorimetry (DSC), linear sweep voltammetry (LSV) and AC complex impedance measurements. In systems with 11 wt% of acrylonitrile all liquid electrolytes were obtained regardless of lithium ion concentration. Complex impedance measurements with stainless steel electrodes give ambient ionic conductivities $8.1\times10^{-6}\sim1.4\times10^{-4}S cm^{-1}$. On the other hand, a hard and soft films at ambient temperature were obtained in copolymer electrolyte system consists of 15 wt% acrylonitrile with 6 : 1 and 3 : 1 of [EO] : [Li] ratio, respectively. DSC measurements indicate the crystalline melting temperature of poly(PEGMA) disappeared completely after addition of $LiClO_4$ in this system due to the complex formation between ethylene oxide (EO) unit and lithium salt. As a result, free standing film with room temperature ionic conductivity of $1.7\times10^{-4}S cm^{-1}$ and high electrochemical stability up to 5.5V was obtained by controlling of acrylonitrile and lithium salt concentration.

• Journal of the Korean Electrochemical Society
• /
• v.14 no.2
• /
• pp.92-97
• /
• 2011

In this study we have investigated the Li-ion coordination, thermal behavior and electrochemical stability of N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ($Py_{14}TFSI$) with lithium bis(trifluoromethanesulfony)imide (LiTFSI) doping intended for use as electrolytes for lithium batteries. The ionic conductivity is reduced and glass transition temperature ($T_g$) increases with LiTFSI doping concentration. Also, the electrochemical stability increases with LiTFSI doping. A high LiTFSI doping could enhance the electrochemical stability of electrolytes for lithium batteries, whereas the decrease in the ionic conductivity limits the capacity of the battery.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.3
• /
• pp.294-301
• /
• 2019

The quasi-solid-state hybrid electrolytes were synthesized by chemical cross-linking reaction of methacrylate-functionalized $SiO_2$ ($MA-SiO_2$) and tetra (ethylene glycol) diacrylate in aqueous electrolyte. A quasi-solid-state electrolyte synthesized by 6 wt.% $MA-SiO_2$ exhibited a high ionic conductivity of $177mS\;cm^{-1}$ at room temperature. The electrochemical $H_2$ sensor assembled with quasi-solid-state electrolyte showed relatively fast response and high sensitivity for hydrogen gas at ambient temperature, and exhibited better durability and stability than the liquid electrolyte-based sensor. The simple construction of the sensor and its sensing characteristics make the quasi-solid-state hydrogen sensor promising for practical application.

• Journal of the Korean Electrochemical Society
• /
• v.16 no.1
• /
• pp.30-38
• /
• 2013

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deionized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under conditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different features. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

• Journal of the Korean Electrochemical Society
• /
• v.14 no.1
• /
• pp.9-15
• /
• 2011

The composite membranes comprising of sulfonated polymers as matrix and ionic liquids as ion-conducting medium in replacement of water are studied to investigate the effect of annealing of the sulfonated polymers. The polymeric membranes are prepared on recast Nafion containing the ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ($EMIBF_4$). The composite membranes are characterized by thermogravitational analyses, ion conductivity and small-angle X-ray scattering. The composite membranes annealed at $190^{\circ}C$ for 2 h after the fixed drying step showed better ionic conductivity, but no significant increase in thermal stability. The mean Bragg distance between the ionic clusters, which is reflected in the position of the ionomer peak (small-angle scattering maximum), is larger in the annealed composite membranes containing $EMIBF_4$ than the non-annealed ones. It might have been explained to be due to the different level of ion-clustering ability of the hydrophilic parts (i.e., sulfonic acid groups) in the non- and annealed polymer matrix. In addition, the ionic conductivity of the membranes shows higher for the annealed composite membranes containing $EMIBF_4$. It can be concluded that the annealing of the composite membranes containing ionic liquids due to an increase in ion-clustering ability is able to bring about the enhancement of ionic conductivity suitable for potential use in proton exchange membrane fuel cells (PEMFCs) at medium temperatures ($150-200^{\circ}C$) in the absence of external humidification.

• Journal of Pharmaceutical Investigation
• /
• v.25 no.3
• /
• pp.239-247
• /
• 1995

The physico-chemical stability of aucubin, a hepatoprotective iridoid glucoside, in buffered aqueous solutions was studied using a stability-indicating reversed-phase high performance liquid chromatography. The degradation of aucubin followed the pseudo-first-order kinetics. In strong acidic regions, aucubin was rapidly degraded by the specific acid catalysis, forming dark brown precipitates. From the rate-pH profiles, it was found that aucubin was most stable at the pH of about 10. From the temperature dependence of degradation, activation energies for aucubin at pH 2.1 and 4.9 were calculated to be 22.0 and 24.3 kcal/mole, respectively. The shelf-life $(t_{90%})$ for aucubin at pH 9.07 and $20^{\circ}C$ was predicted to be about 603 days. A higher ionic strength accelerated the degradation of aucubin at pH 4.01. The effect of metal ions on the degradation rate of aucubin at pH 7.16 was in the rank order of $Cu^{2+}\;>\;Fe^{3+}\;>\;Co^{2+}\;>\;Fe^{2+}\;>\;Mg^{2+}$. On the other hand, $Mn^{2+}\;and\;Ba^{2+}$ slowed the degradation rate.

• Ceramist
• /
• v.21 no.4
• /
• pp.349-365
• /
• 2018

Since the electrification of vehicles has been extended, solid-state batteries have been attracting a lot of interest because of their superior safety. Especially, polymer, sulfide, and oxide based materials are being studied as solid electrolytes, and each type of materials has advantaged and disadvantages over others. Oxide electrolytes has higher chemical and electrochemical stability compared to the other types of electrolytes. However, ionic conductivity isn't high enough as much as that of organic liquid electrolytes. Also, there are many difficulties of fabricating solid-state batteries with oxide based electrolytes because they require a sintering process at very high temperature (above ${\sim}800^{\circ}C$). Herein, we review recent studies of solid-state batteries with oxide based electrolytes about the ionic conductivity, interfacial reactions with Li metal, and preparation of solid-state cell.

• Korean Chemical Engineering Research
• /
• v.50 no.1
• /
• pp.35-40
• /
• 2012

In this study, 1-(2-methoxyethyl)-3-methylimidazolium methanesulfonate ionic liquid has been synthesized, characterized and tested with respect to carbon dioxide absorption with the aim to use it as advanced absorbent materials in fossil fuel processing. The ionic liquid was synthesized by a one step method, low cost. The thermal and chemical stability of selected ionic liquid has been investigated by DSC, TGA and the structure was verified by $^1H$-NMR spectroscopy. The solubility of carbon dioxide in the methanesulfonate-based ionic liquids were measured using a high-pressure equilibrium apparatus equipped with a variable-volume view cell at 30, 50 and $70^{\circ}C$ and pressure up to 195 bar. The results show that carbon dioxide solubilities of 1-(2-methoxyethyl)-3-methylimidazolium methanesulfonate increased with pressure increasing and temperature decreasing, and the carbon dioxide absorption capacity showed 27.6 $CO_2/IL$(g/kg) at $30^{\circ}C$, 13 bar.