• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.6
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• pp.89-97
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• 2022

Ultrasonic metal welding has been widely used for joining lithium-ion battery tabs. Weld quality monitoring has been an important issue in lithium-ion battery manufacturing. This study focuses on the weld quality monitoring in ultrasonic metal welding with the longitudinal-torsional vibration mode horn developed newly. As the quality of ultrasonic welding depends on welding parameters like pressure, time, and amplitude, the suitable values of these parameters were selected for experimentation. The welds were tested via tensile testing machine and weld strengths were investigated. The dataset collected for performance test was used to train the multi-layer perceptron neural network. The three layer neural network was used for the study and the optimum number of neurons in the first and second hidden layers were selected based on performances of each models. The best models were selected for the horn and then tested to see their performances on an unseen dataset. The neural network models for the longitudinal-torsional mode horn attained test accuracy of 90%. This result implies that proposed models has potential for the weld quality monitoring.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.131-136
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• 2008

Silica- or titania-filled poly (vinylidene fluoride-co-hexafluoropropylene)-based polymer electrolytes were prepared by phase inversion technique using N-methyl-2-pyrrolidone and dimethyl acetamide as solvent and water as non-solvent. The polymer electrolytes were adopted to the lithium metal polymer battery using high-capacity cathode $Li[Ni_{0.15}Co_{0.10}Li_{0.20}Mn_{0.55}]O_2$ and lithium metal anode. After the repeated charge-discharge test for the cell, it was proved that the cell adopting the polymer electrolyte based on the phase-inversion membrane containing 40~50 wt% silica showed the highest discharge capacity (180 mAh/g) until 80th cycle and then abrupt capacity fade was just followed. The capacity fade might be due to the deposition of lithium dendrite on the polymer electrolyte, in which the capacity retention was no longer sustainable.

• ETRI Journal
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• v.26 no.4
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• pp.285-291
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• 2004

We prepared a novel multi-functional dual-layer polymer electrolyte by impregnating the interconnected pores with an ethylene carbonate (EC)/dimethyl carbonate (DMC)/lithium hexafluorophosphate $(LiPF_6)$ solution. The first layer, based on a microporous polyethylene, is incompatible with a liquid electrolyte, and the second layer, based on poly (vinylidenefluoride-co-hexafluoropropylene), is submicroporous and compatible with an electrolyte solution. The maximum ionic conductivity is $7{\times}10^{-3}S/cm$ at ambient temperature. A unit cell using the optimum polymer electrolyte showed a reversible capacity of 198 mAh/g at the 500th cycle, which was about 87% of the initial value.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.665-667
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• 2013

Metal ions show various transitions in the cathode of a lithium-ion battery. The diffusion process of lithiumions and the phase transition in the cathode need to be thoroughly understood for the advanced design of an improved lithium-ion battery. Here, we employ a phase field model to simulate the diffusion of lithiumions and to study the phase transition in the cathode.

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.206-213
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• 2016

Transition metal oxide-based electrodes for lithium ion batteries have recently attracted much attention because of their high theoretical capacity. Here we report the electrochemical behavior of cobalt oxide nanorods as anodes, prepared by a template-free, one-step electrochemical deposition of cobalt nanorods, followed by an oxidation process. The as-deposited cobalt has a slightly convex columnar structure, and controlled thermal oxidation produces cobalt oxides of different Co/O ratios, while the original shape is largely preserved. As an anode in a rechargeable lithium battery, the Co/O ratio has a strong effect on initial capacity and cycling stability. In particular, the one-dimensional Co@Co_xO_y core shell structure obtained from a mild heat-treatment results in superior cycling stability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.444-447
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• 2002

The Jig cells are fabricated in the drying room, and consisted of elemental sulfur used as a cathode active material, lithium metal used as a anode material and 1M $LiCF_{3}SO_{3}$ dissolved in TG (Tetraglyme)/DIOX (1,3-Dioxolane) used as a electrolyte. The four kinds of electrolytes with different content of TG and DIOX are prepared. The electrochemical properties of the foregoing electrolytes-based lithium sulfur batteries are analyzed by AC impedance experiments. The conductivity of four different electrolytes is investigated. The conductivity of electrolyte [1M $LiCF_3SO_3$ dissolved in TG/DIOX (50:50, vol.)] is higher than that of other three kinds of electrolytes with different volume ratio (70:30, 30:70) and single solvent (TG).

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.136-142
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• 2011

$Li_4Ti_5O_{12}$ is prepared through a solid-state reaction between $Li_2CO_3$ and anatase $TiO_2$ for applications in lithium-ion batteries. The rate capability is measured and the electrode polarization is analyzed through the galvanostatic intermittent titration technique (GITT). The rate characteristics and electrode polarization are highly sensitive to the amount of carbon loading. Polarization of the $Li_4Ti_5O_{12}$ electrode continuously increases as the reaction proceeds in both the charge and discharge processes. This relation indicates that both electron conduction and lithium diffusion are significant factors in the polarization of the electrode. The transition metal (Cu, Ni, Fe) ion added during the synthesis of $Li_4Ti_5O_{12}$ for improving the electrical conductivity also greatly enhances the rate capability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.387-390
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• 1998

New Ag-deposited graphite anodes were developed using wet chemical reduction methods for depositing Ag metal onto graphite particles. In this paper, we investigated X-ray diffraction pattern and charge-discharge behavior for Ag-deposited graphite anode. The Lithium ion cello using Ag-deposited graphite anode showed a high average discharge voltage of 3.6∼3.W and a excellent cycle ability than that of conventional graphite. Little capacity loss in this battery may be due to the highly durable Ag-deposited graphite anodes.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.168-172
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• 2018

This study first investigates the effect of the choice of cation on three different ionic-liquid-based gel polymer electrolytes (ILPEs) with polyimide membranes. The preparation of three ILPEs based on electrospun membranes of PI and incorporating a room-temperature ionic liquid, 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide complexed with lithium bis(trifluoromethylsulfonyl)imide, is described. ILPE-EMImTFSI has an ionic conductivity as high as $5.3{\times}10^{-3}S\;cm^{-1}$ at $30^{\circ}C$. Furthermore, it shows higher thermal stability and electrochemical oxidation stability compared to the other two ILPEs because of its stronger bonds. These results indicate that polyimide-based ILPE-EMImTFSI is a good candidate for use in high-safety rechargeable lithium metal batteries.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.250-255
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• 2019

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) show promise for improving the lithium ion battery safety. However, due to oxidation of the PEO group and corrosion of the Al current collector, PEO-based SPEs have not previously been effective for use in $LiCoO_2$ (LCO) cathode materials at room temperature. In this paper, a semi-interpenetrating polymer network (semi-IPN) PEO-based SPE was applied to examine the performance of a LCO/SPE/Li metal cell at different voltage ranges. The results indicate that the SPE can be applied to LCO-based lithium polymer batteries with high electrochemical performance. By using a carbon-coated aluminum current collector, the Al corrosion was mostly suppressed during cycling, resulting in improvement of the cell cycle stability.