• Journal of Electrochemical Science and Technology
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• v.2 no.1
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• pp.8-13
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• 2011

Interfacial compatibility between the Si-Cu electrode and diluted ionic liquid electrolyte containing 50 vol.% of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPP-TFSI) and 50 vol.% dimethyl carbonate (DMC) in a lithium cell and dilution effect on surface chemistry are examined. ex-situ ATR FTIR analysis results reveal that the surface of the Si-Cu electrode cycled in the diluted ionic liquid electrolyte is effectively passivated with the SEI layer mainly composed of carboxylate salts-containing polymeric compounds produced by the decomposition of DMC. Surface species by the decomposition of TFSI anion and MPP cation are found to be relatively in a very low concentration level. Passivation of electrode surface with the SEI species contributes to protect from further interfacial reactions and to preserve the electrode structure over 200 cycles, delivering discharge capacity of > 1670 $mAhg^{-1}$ and capacity retention of 88% of maximum discharge capacity.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.51-54
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• 2007

Top-emission 3.5 inch qVGA IOD (Inverted AMOLED) was fabricated with inverted EL structure driven by a-Si TFT backplane. In order to get stable driving TFT, we used FCP(Field Control Plate) layer which was connected with the source of the driving TFT. And we developed planarization process to planarize the cathode layer which was the bottom layer of inverted OLED. Our unique IOD structure is “a-Si TFT/ Al(Cathode)/ LiF/ LG-201(ETL)/ EML(RGB)/ HTL/ LG-101(HIL & Buffer layer)/ IZO(Anode)”. LG-201(ETL) layer was studied for more efficient electron injection from cathode to EML, and LG-101(HIL & Buffer layer) covered by IZO anode was also explored for decreasing the EL surface damage.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.159-166
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• 2022

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g^-1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g^-1, shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.139-142
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• 2018

Silicon (Si) is a promising anode material for next-generation lithium ion batteries (LIBs) because of its high capacity of 4,200 mAh/g ($Li_{4.4}Si$ phase). However, the large volume expansion of Si during lithiation leads to electrical failure of electrode and rapid capacity decrease. Generally, a binder is homogeneously mixed with active materials to maintain electrical contact, so that Si needs a particular binding system due to its large volume expansion. Polyvinyl alcohol (PVA) is known to form a hydrogen bond with partially hydrolyzed silicon oxide layer on Si nanoparticles. However, the decrease of its cohesiveness followed by the repeated volume change of Si still remains unsolved. To overcome this problem, we have introduced the electrospinning method to weave active materials in a stable nanofibrous PVA structure, where stresses from the large volume change of Si can be contained. We have confirmed that the capacity retention of Si-based LIBs using electrospun PVA matrix is higher compared to the conservative method (only dissolving in the slurry); the $25^{th}$ cycle capacity retention ratio based on the $2^{nd}$ cycle was 37% for the electrode with electrospun PVA matrix, compared to 27% and 8% for the electrodes with PVdF and PVA binders.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.70-77
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• 2019

$SiO_x$ nanoparticles were granulated, and their microstructures and effects on electrochemical behaviors were investigated. In spite of the promising electrochemical performance of $SiO_x$, nanoparticles have limitations such as high surface area, low density, and difficulty in handling during slurry processing. Granulation can be one solution. In this study, pelletizing and annealing were conducted to create particles with sizes of several decades of micron. Decrease in surface area directly influences the initial charge and discharge process when granules are applied as anode materials for Li-ion batteries. Lower surface area is key to decreasing the amount of irreversible phase-formation, such as $Li_2Si_2O_5$, $Li_2SiO_3$ and $Li_4SiO_4$, as well as forming the solid electrolyte interface. Additionally, aggregation of nanoparticles is required to obtain further enhancement of the electrochemical behavior due to restrictions that there be no $Li_4SiO_4$-related reaction during the first discharge process.

• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.429-440
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• 2023

1,1-Dialkyl-2,5-bis(trimethylsilylethynyl)-3,4-diphenylsiloles (R=Et, i-Pr, n-Hex; 3a-c) were prepared and utilized as anode active materials for lithium-ion batteries; 3a was also used as a filler for the solid-state electrolytes (SSE). Siloles 3a-c were prepared by substitution reactions in which the two bromine groups of 1,1-dialkyl-2,5-dibromo-3,4-diphe- nylsiloles, used as precursors, were substituted with trimethylsilylacetylene in the presence of palladium chloride, copper iodide, and triphenylphosphine in diisopropylamine. Among siloles 3a-c, 3a had the best electrochemical properties as an anode material for lithium-ion batteries, including an initial capacity of 758 mAhg^-1 (0.1 A/g), which was reduced to 547 mAhg^-1 and then increased to 1,225 mAhg^-1 at 500 cycles. A 3a-composite polymer electrolyte (3a-CPE) was prepared using silole 3a as an additive at concentrations of 1, 2, 3, and 4 wt.%. The 2 wt.% 3a-CPE composite afforded an excellent ionic conductivity of 1.09 × 10^-3 Scm^-1 at 60℃, indicating that silole 3a has potential applicability as an anode active material for lithium-ion batteries, and can also be used as an additive for the SSE of lithium-ion batteries.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.47-50
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• 2008

A new anode composition material comprising of SiO and Graphite has been prepared by adopting High energy ball milling (HEBM) technique. The anode material shows high initial charge and discharge capacity values of 1139 and 568 mAh/g, respectively. The electrode sustains reversible discharge capacity value of 719 mAh/g at 30th cycle with a high coulombic efficiency${\sim}99%$. Since the materials formed during initial charge process the nano silicon/$Li_4SiO_3$ and $Li_2O$ remains as interdependent, it may be expected that the composite exhibiting higher amount of irreversibility$(Li_2O)$ will deliver higher reversible capacity. In this study, constant current-constant voltage (CC-CV) charge method was employed in place of usual constant current (CC) method in order to convert efficiently all the SiO particles which resulted high initial discharge capacity at the first cycle. We improved considerably the initial discharge specific capacity of SiO/G composite by pretreatment(CC-CV).

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.439-445
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• 2022

In this study, Silicon and petroleum pitch were coated on the surface of Si/C fiber manufactured using electrospinning to improve the electrochemical performances. SiO₂/PAN fiber was prepared by electrospinning with TEOS and PAN at various ratios dissolved in DMF. The characteristics of carbonization, reduction, and pitch coating processes were investigated for the optimal process of the pitch coated Si/C fiber anode composite. Anode composite prepared with TEOS/PAN = 4/6 (CR-46) after carbonization and reduction process has a capacity of 657 mAh/g. To improve capacity and stability, Si powder and PFO pitch were coated at the surface of CR-46. When the pitch composition was fixed at 10 wt%, it was found that the capacity increased as the weight ratio of silicon increased, but the stability decreased. The pitch coated Si/C fiber composite with 10 wt% silicon has high capacity of 982.4 mAh/g and capacity retention of 86.1%. In the test to evaluate rate performance, the rate capability was 80.2% (5C/0.1C).

• 전자공학회논문지 IE
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• v.44 no.3
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• pp.1-5
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• 2007

A new field emission tip array was realized by Ti silicidation of Ti coated Si tip, which has long term durability, chemical stability, and high emission current density. The fabricated Ti silicided FE tip array under high vacuum condition of about $10^{-8}Torr$ shows that the turn-on voltage is about 40V and the emission current is about $69{\mu}A$ when the bias of 150V is applied between anode and cathode of $100{\mu}m$ distance.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.685-688
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• 2002

In this paper, it is reported that the anode current changes at the constantly applied gate voltages and the current-voltage (I-V) characteristics of Si, Co silicide and Mo silicide field emitter arrays (FEAs) depending on vacuum level from a $10^{-9}$ torr to a $10^{-6}$ torr. The mechanism of the robustness of anode current degradation of Mo silicide FEAs under poor vacuum conditions can be explained by the model of tolerance for the oxygen adsorption and oxidation at the silicide surface. Also, we present the changes of emitting area and work function of the emitters according to vacuum level.