• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.362-368
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• 2022

The application of polymer composite electrolyte in all-solid-state lithium-sulfur battery (ASSLSBs) can guarantee high energy density and improve the interface contact between electrolyte and electrode, which has a broader application prospect. However, the inherent insulation of the sulfur-cathode leads to a low electron/ion transfer rate. Carbon materials with high electronic conductivity and electrolyte materials with high ionic conductivity are usually selected to improve the electron/ion conduction of the composite cathode. In this work, PEO-LiTFSI-LLZO composite polymer electrolyte (CPE) with high ionic conductivity was prepared. The ionic conductivity was 1.16×10^-4 and 7.26×10^-4 S cm^-1 at 20 and 60℃, respectively. Meanwhile, the composite sulfur cathode was prepared with Sulfur, reduced graphene oxide and composite polymer electrolyte slurry (S-rGO-CPEs). In addition to improving the ion conductivity in the cathode, CPEs also replaces the role of binder. The influence of different contents of CPEs in the cathode material on the performance of the constructed battery was investigated. The results show that the electrochemical performance of the all-solid-state lithium-sulfur battery is the best when the content of the composite electrolyte in the cathode is 40%. Under the condition of 0.2C and 45℃, the charging and discharging capacity of the first cycle is 923 mAh g^-1, and the retention capacity is 653 mAh g^-1 after 50 cycles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.792-801
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• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.409-409
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• 2011

All solid-state thin film lithium batteries have many applications in miniaturized devices because of lightweight, long-life, low self-discharge and high energy density. The research of cathode materials for thin film lithium batteries that provide high energy density at fast discharge rates is important to meet the demands for high-power applications. Among cathode materials, lithium manganese oxide materials as spinel-based compounds have been reported to possess specific advantages of high electrochemical potential, high abundant, low cost, and low toxicity. However, the lithium manganese oxide has problem of capacity fade which caused by dissolution of Mn ions during intercalation reaction and phase instability. For this problem, many studies on effect of various transition metals have been reported. In the preliminary study, the Sn-substituted LiMn2O4 thin films prepared by pulsed laser deposition have shown the improvement in discharge capacity and cycleability. In this study, the thin films of LiMn2O4 and LiSn0.0125Mn1.975O4 prepared by RF magnetron sputtering were studied with effect of deposition parameters on the phase, surface morphology and electrochemical property. And, all solid-state thin film batteries comprised of a lithium anode, lithium phosphorus oxy-nitride (LiPON) solid electrolyte and LiMn2O4-based cathode were fabricated, and the electrochemical property was investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.194-198
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• 2022

All-solid-state thin-film battery can realize the integration of electronic circuits into small devices. However, a high voltage cathode material is required to compensate for the low energy density. Therefore, it is necessary to study all-solid-state thin-film battery based on the high voltage cathode material LNMO. Nevertheless, the electrochemical properties deteriorate due to the problem of the interface between LiNi_0.5Mn_1.5O₄ (LNMO) and the solid electrolyte LiPON. In this study, to solve this problem, amorphous V₂O₅ was deposited as an interlayer between LNMO and LiPON. We confirmed the possibility of improving cycle performance of LNMO based thin-film battery. We expect that the results of this study can extend the battery lifespan of small devices using LNMO based all-solid-state thin-film battery.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.209-211
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• 2001

The core in developing the transformer-operated 3 phase solid state meter is to design a single chip IC, that incorporates all the necessary features required for development of the 3 phase solid state meter. Using this technology, the solid state meter can be mass produced at lower cost and higher quality. This report deals with the performance of the prototype FPGA board, which is the final step before actual IC fabrication in fabrication LAB. All the features of FPGA board, shown in this report will be included in the final ASIC IC product.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.4
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• pp.368-376
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• 2012

According to developed distributed generators, Solid State Circuit Breaker(SSCB) is essential for high power quality of DC Grid. In this paper, a simple and new structure of DC SSCB with a fast circuit breaker and fault current limiter is proposed. It can help to choice low specification of elements because of the limiting of fault current and achieve economic efficiency for minimizing auxiliary SCRs. Also all of SCRs have little switching loss because they operate under ZVS and ZCS. Through simulations and experiments of short-circuit fault, the performance characteristic of proposed circuit is verified and a guideline is so suggested that the DC SSCB is applied for a different DC grid using formulas.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.800-802
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• 1999

The meters for low voltage customer presently being used in Korea are all mechanical type and there is strict limitation on applying various customized tariff structure. Recently low voltage solid state meter is under development by several makers of the watt hour meter in Korea. Also, KEPCO has a plan to use the solid state meter for low voltage customer to reduce peak power. So, this paper suggests the needed function of low voltage solid state meter considering electricity tariff policy.

• 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 the Korean Ceramic Society
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• v.54 no.3
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• pp.217-221
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• 2017

Improvement studies of existing phosphors are needed for use in light emitting diodes (LEDs). Among the phosphors discovered recently, the SLA ($SrLiAl_3N_4:Eu^{2+}$) is a phosphor that has a narrow width. It is now known as a good red phosphor that meets the industry's needs for warm white (color temperature ranging from 2700 to 4000 K) and high CRI (> 80). However, SLA phosphors are obtained from difficult synthetic methods. All commercially available phosphors should be derived from the general solid state synthesis method. The phosphors produced by difficult synthetic methods will inevitably fall out of price competitiveness and will be scrapped. This study succeeded in synthesizing SLA ($SrLiAl_3N_4:Eu^{2+}$) phosphors by using a general solid phase synthesis method based on the reaction energy obtained from DFT calculations. As a result, we found an optimal solid state synthesis method for SLA phosphors.