• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.151.1-151
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• 1998

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.411-420
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• 2020

Undesirable interfacial reactions between the cathode and sulfide electrolyte deteriorate the electrochemical performance of all-solid-state cells based on sulfides, presenting a major challenge. Surface modification of cathodes using stable materials has been used as a method for reducing interfacial reactions. In this work, a precursor-based surface modification method using Zr and Mo was applied to a LiNi_0.6Co_0.2Mn_0.2O₂ cathode to enhance the interfacial stability between the cathode and sulfide electrolyte. The source ions (Zr and Mo) coated on the precursor-surface diffused into the structure during the heating process, and influenced the structural parameters. This indicated that the coating ions acted as dopants. They also formed a homogenous coating layer, which are expected to be layers of Li-Zr-O or Li-Mo-O, on the surface of the cathode. The composite electrodes containing the surface-modified LiNi_0.6Co_0.2Mn_0.2O₂ powders exhibited enhanced electrochemical properties. The impedance value of the cells and the formation of undesirable reaction products on the electrodes were also decreased due to surface modification. These results indicate that the precursor-based surface modification using Zr and Mo is an effective method for suppressing side reactions at the cathode/sulfide electrolyte interface.

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.407-415
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• 2022

Surface coating of cathodes is an essential process for all-solid-state batteries (ASSBs) based on sulfide electrolytes as it efficiently suppresses interfacial reactions between oxide cathodes and sulfide electrolytes. Based on computational calculations, Li₃PO₄ has been suggested as a promising coating material because of its higher stability with sulfides and its optimal ionic conductivity. However, it has hardly been applied to the coating of ASSBs due to the absence of a suitable coating process, including the selection of source material that is compatible with ASSBs. In this study, polyphosphoric acid (PPA) and (NH₄)₂HPO₄ were used as source materials for preparing a Li₃PO₄ coating for ASSBs, and the properties of the coating layer and coated cathodes were compared. The Li₃PO₄ layer fabricated using the (NH₄)₂HPO₄ source was rough and inhomogeneous, which is not suitable for the protection of the cathodes. Moreover, the water-based coating solution with the (NH₄)₂HPO₄ source can deteriorate the electrochemical performance of high-Ni cathodes that are vulnerable to water. In contrast, when an alcohol-based solvent was used, the PPA source enabled the formation of a thin and homogeneous coating layer on the cathode surface. As a consequence, the ASSBs containing the Li₃PO₄-coated cathode prepared by the PPA source exhibited significantly enhanced discharge and rate capabilities compared to ASSBs containing a pristine cathode or Li₃PO₄-coated cathode prepared by the (NH₄)₂HPO₄ source.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.429-434
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• 2022

There is ongoing research to develop lithium ion batteries as sustainable energy sources. Because of safety problems, solid state batteries, where electrolytes are replaced with solids, are attracting attention. Sulfide electrolytes, with a high ion conductivity of 10^-3 S/cm or more, have the highest potential performance, but the price of the main materials is high. This study investigated lithium hydride materials, which offer economic advantages and low density. To analyze the change in ion conductivity in polymer electrolyte composites, PVDF, a representative polymer substance was used at a certain mass ratio. XRD, SEM, and BET were performed for metallurgical analyses of the materials, and ion conductivity was calculated through the EIS method. In addition, thermal conductivity was measured to analyze thermal stability, which is a major parameter of lithium ion batteries. As a result, the ion conductivity of LiH was found to be 10^-6 S/cm, and the ion conductivity further decreased as the PVDF ratio increased when the composite was formed.

• Journal of the Korean Electrochemical Society
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• v.25 no.3
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• pp.95-104
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• 2022

The development of non-flammable all-solid-state batteries (ASSLBs) has become a hot topic due to the known drawbacks of commercial lithium-ion batteries. As the possibility of applying sulfide solid electrolytes (SSEs) for electric vehicle batteries increases, efforts for the low-cost mass-production are actively underway. Until now, most studies have used high-energy mechanical milling, which is easy to control composition and impurities and can reduce the process time. Through this, various SSEs that exceed the Li⁺ conductivity of liquid electrolytes have been reported, and expectations for the realization of ASSLBs are growing. However, the high-energy mechanical milling method has disadvantages in obtaining the same physical properties when mass-produced, and in controlling the particle size or shape, so that physical properties deteriorate during the full process. On the other hand, wet chemical synthesis technology, which has advantages in mass production and low price, is still in the initial exploration stage. In this technology, SSEs are mainly manufactured through producing a particle-type, solution-type, or mixed-type precursor, but a clear understanding of the reaction mechanism hasn't been made yet. In this review, wet chemical synthesis technologies for SSEs are summarized regarding the reaction mechanism between the raw materials in the solvent.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.111-129
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• 2019

Recently, all-solid-state batteries (ASSBs) have attracted increasing interest owing to their higher energy density and safety. As the core material of ASSBs, the characteristics of the solid electrolyte largely determine the performance of the battery. Thus far, a variety of inorganic solid electrolytes have been studied, including the NASICON-type, LISICON-type, perovskite-type, garnet-type, glassy solid electrolyte, and so on. The garnet Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte is one of the most promising candidates because of its excellent comprehensively electrochemical performance. Both, experiments and theoretical calculations, show that cubic LLZO has high room-temperature ionic conductivity and good chemical stability while contacting with the lithium anode and most of the cathode materials. In this paper, the crystal structure, Li-ion transport mechanism, preparation method, and element doping of LLZO are introduced in detail based on the research progress in recent years. Then, the development prospects and challenges of LLZO as applied to ASSBs are discussed.

• International journal of advanced smart convergence
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• v.13 no.1
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• pp.206-211
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• 2024

This study used a total of 205,565 datasets of 'voltage', 'current', '℃', and 'time(s)' to systematically analyze the properties and performance of solid electrolytes. As a method for characterizing solid electrolytes, a linear regression model, one of the machine learning models, is used to visualize the relationship between 'voltage' and 'current' and calculate the regression coefficient, mean squared error (MSE), and coefficient of determination (R^2). The regression coefficient between 'Voltage' and 'Current' in the results of the linear regression model is about 1.89, indicating that 'Voltage' has a positive effect on 'Current', and it is expected that the current will increase by about 1.89 times as the voltage increases. MSE found that the mean squared error between the model's predicted and actual values was about 0.3, with smaller values closer to the model's predictions to the actual values. The coefficient of determination (R^2) is about 0.25, which can be interpreted as explaining 25% of the data.

• Journal of Electrochemical Science and Technology
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• v.11 no.3
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• pp.282-290
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• 2020

In this article, we report the effect of blended cathode materials on the performance of all-solid-state lithium-ion batteries (ASLBs) with oxide-based organic/inorganic hybrid electrolytes. LiFePO₄ material is good candidates as cathode material in PEO-based solid electrolytes because of their low operating potential of 3.4 V; however, LiFePO₄ suffers from low electric conductivity and low Li ion diffusion rate across the LiFePO₄/FePO₄ interface. Particularly, monoclinic Li₃V₂(PO₄)₃ (LVP) is a well-known high-power-density cathode material due to its rapid ionic diffusion properties. Therefore, the structure, cycling stability, and rate performance of the blended LiFePO₄/Li₃V₂(PO₄)₃ cathode material in ASLBs with oxidebased inorganic/organic-hybrid electrolytes are investigated by using powder X-ray diffraction analysis, field-emission scanning electron microscopy, Brunauer-Emmett-Teller sorption experiments, electrochemical impedance spectroscopy, and galvanostatic measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.445-450
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• 2024

The expansion of lithium-ion battery usage beyond portable electronic devices to electric vehicles and energy storage systems is driven by their high energy density and favorable cycle characteristics. Enhancing the stability and performance of these batteries involves exploring solid electrolytes as alternatives to liquid ones. While sulfide-based solid electrolytes have received significant attention for commercialization, research on amorphous-phase glass solid electrolytes in oxide-based systems remains limited. Here, we investigate the glass transition temperatures and sintering behaviors by changing the molecular ratio of Li₂O/B₂O₃ in borate glass comprising Li₂O-B₂O₃-Al₂O₃ system. The glass transition temperature is decreasing as increasing the amount of Li₂O. When we sintered at 450℃, just above the glass transition temperature, the samples did not consolidate well, while the proper sintered samples could be obtained under the higher temperature. We successfully obtained the borate glass ceramics phases by melt-quenching method, and the sintering characteristics are investigated. Future studies could explore optimizing ion conductivity through refining processing conditions, adjusting the glass former-to-modifier ratio, and incorporating additional Li salt to enhance the ionic conductivity.

• Korean Journal of Materials Research
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• v.8 no.4
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• pp.323-327
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• 1998

All solid state lithium based rechargeable batteries were fabricated in a cell structure of Li/PEO-$LiCIO_4$-PC /$LIMn_2O_4$$LIMn_2O_4$ thin films were prepared by RF magnetron sputtering and the spinel structure could be obtained by Rapid Thermal Annealing (RT A) process at the temperature of around 750$750^{\circ}C$ . Room temperature cycling of this cell showed a nearly constant cell potential of 4 V( us. Li) and good reversibility.