• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.63-68
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• 2016

$Li_4Ti_5O_{12}$ is prepared through a solid-state reaction between anatase $TiO_2$ and $Li_2CO_3$ for the negative electrode active materials in quick-charging lithium-ion batteries. The small amount of carbon black (0, 0.5, 1.0, and 3.0 wt%) is added for the reduction of powder agglomeration during heat-treatment. As the amount of the added carbon black increases, the tap density of $Li_4Ti_5O_{12}$ powder gradually decreases. Furthermore, the $Li_4Ti_5O_{12}$ powder prepared with 1.0 wt% of carbon black shows the highest sieved fraction at the powder classification by 325 mesh standard sieve. The $Li_4Ti_5O_{12}$ powders with various contents of carbon black are almost same at the rate capability for the negative electrode materials in lithium-ion batteries.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.419-420
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• 2012

Lithium-ion battery (LIB) usually used for valuable electronic devices are extended to applications. High stability negative electrode materials for LIB were investigated using electrodeposition of nanoparticles (NPs) on the nanostructured carbon. NPs with about 70 nm diameters were evenly prepared on the graphitic carbon materials using electrodeposition process at room temperature. It was observed that the NPs were homogeneously embedded into not only external surface but bottom part of the graphitic carbon network. The graphitic carbon material covered with NPs enables facile electron transport owing to the network structure and improves structural collapse during cycling. This facile room temperature process is expected to be applicable to other anode materials such as Sn and Al for the anode of LIB.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.277-277
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• 2010

The capacity of the carbonaceous materials reached ca. $350\;mAhg^{-1}$ which is close to theorestical value of the carbon intercalation composition $LiC_6$, resulting in a relatively low volumetric Li capacity. Notwithstanding the capacities of carbon, it will not adjust well to the need so future devices. Silicon shows the highest gravimetric capacities (up to $4000\;mAhg^{-1}$ for $Li_{21}Si_5$). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. We focused on electrode materials in the multiphase form which were composed of two metal compounds to reduce the volume change in material design. A combination of electrochemically amorphous active material in an inert matrix (Si-M) has been investigated for use as negative electrode materials in lithium ion batteries. The matrix composited of Si-M alloys system that; active material (Si)-inactive material (M) with Li; M is a transition metal that does not alloy with Li with Li such as Ti, V or Mo. We fabricated and tested a broad range of Si-M compositions. The electrodes were sputter-deposited on rough Cu foil. Electrochemical, structural, and compositional characterization was performed using various techniques. The structure of Si-M alloys was investigated using X-ray Diffractometer (XRD) and transmission electron microscopy (TEM). Surface morphologies of the electrodes are observed using a field emission scanning electron microscopy (FESEM). The electrochemical properties of the electrodes are studied using the cycling test and electrochemical impedance spectroscopy (EIS). It is found that the capacity is strongly dependent on Si content and cycle retention is also changed according to M contents. It may be beneficial to find materials with high capacity, low irreversible capacity and that do not pulverize, and that combine Si-M to improve capacity retention.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1059-1064
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• 1998

We have investigated various kind of graphite and MCMB6-28 to develop carbon negative electrode for lithium ion secondary battery. The interlayer length of them was $3.358{\sim}3.363{\AA}$ and the BET specific surface area was $2.95{\sim}26.15m^2/g$. From this study, When the interlayer of them was large and the BET specific surface area was high, the electrochemical characteristics of them was very excellent. Adding 0, 3, 5, wt% of KJ-Black as conducting agent to various graphitic carbon active materials, interface resistance of electrode and electrolyte was less, but rechargeability was better at 3 wt%. At constant current charge and discharge test, discharge capacity was small according to large current.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.458-464
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• 2021

Lithium ion batteries (LIBs) is a kind of rechargeable secondary battery, developed from lithium battery, lithium ions move between the positive and negative electrodes to realize the charging and discharging of external circuits. Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials in which organic imidazole esters are cross-linked to transition metals to form a framework structure. In this article, ZIF-67 is used as a sacrificial template to prepare nano porous carbon (NPC) coated cobalt nanoparticles. The final product Co/NPC composites with complete structure, regular morphology and uniform size were obtained by this method. The conductive network of cobalt and nitrogen doped carbon can shorten the lithium ion transport path and present high conductivity. In addition, amorphous carbon has more pores that can be fully in contact with the electrolyte during charging and discharging. At the same time, it also reduces the volume expansion during the cycle and slows down the rate of capacity attenuation caused by structure collapse. Co/NPC composites first discharge specific capacity up to 3115 mA h/g, under the current density of 200 mA/g, circular 200 reversible capacity as high as 751.1 mA h/g, and the excellent rate and resistance performance. The experimental results show that the Co/NPC composite material improves the electrical conductivity and electrochemical properties of the electrode. The cobalt based ZIF-67 as the precursor has opened the way for the design of highly performance electrodes for energy storage and electrochemical catalysis.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.155-163
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• 2019

Mixture electrodes of a graphite having a good cycle performance and a silicon monoxide (SiO) having a high capacity are fabricated and their cycle performances are evaluated as negative electrodes for lithium-ion batteries. The electrode prepared by mixing the natural graphite and carbon-coated SiO in a mass ratio of 9:1 shows a reversible capacity of $480mAh\;g^{-1}$, 33% higher than that of graphite. However, the capacity deteriorates continuously upon cycling due to the volume change of silicon monoxide. In this study, the factors that can improve the cycle performance have been discussed through the change in the configurations of the electrode and the electrolyte. The electrode using the carboxymethyl cellulose (CMC) binder shows the best cycle performance compared to the conventional binders. The electrode sing the CMC and styrene-butadiene rubber (SBR) binder not only has almost the similar cycle characteristics with the electrode using the CMC binder but also has the better rate capability. When the fluoroethylene carbonate (FEC) is used as an electrolyte additive, the cycle life is improved. However, the electrolyte with 5 wt% of FEC is appropriate because the rate capability decreases when the content of FEC is increased to 10 wt%. In addition, when the mass loading of the electrode is lowered, the cycle performance is greatly improved. Also, enhanced cycle performance is achieved using the roughened Cu current collector polished by abrasive paper.

• Journal of the Korean Chemical Society
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• v.37 no.10
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• pp.881-887
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• 1993

A cobalt(II) ion-selective carbon-paste electrode (CPE) was constructed with ${\iota}$-sparteine. Cobalt(II) ion in aqueous solution was chemically deposited through the complexation with ${\iota}$-sparteine onto the CPE. The surface of CPEs were characterized by cyclic voltammetry and differential pulse voltammetry in an acetate buffer solution, separately. Exposure of the CPEs to an acid solution could regenerate surface to reuse it for the deposition. In more than 5 deposition / measurement / regeneration cycles, the response was reproducible and linear up to $5.0{\times}10^{-6}$M with linear sweep voltammetry. The peaks at 0.17V / 0.27V were correspond to the redox of Co(II)-SP complex deposited on CPE. The anodic peak of which appeared after scan over the cathodic peak of 0.17 V to more negative scan. In case of using the differencial pulse voltammetry (DPV), we have obtained the linear response $2.0{\times}10^{-7}$M with relative standard deviation ${\pm}5.6%$. The detection limit was $1.0{times}10^{-7}$M for 20 minutes of the deposition. We have also investigated the interference effect of various metal ions, which are expected to form the complex with the ligand on the electrode.

• Journal of ILASS-Korea
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• v.22 no.2
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• pp.69-79
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• 2017

When designing a redox flow battery system, compression of battery stack is required to prevent leakage of electrolyte and to reduce contact resistance between cell components. In addition, stack compression leads to deformation of the porous carbon electrode, which results in lower porosity and smaller cross-sectional area for electrolyte flow. In this paper, we investigate the effects of electrode compression on the cell performance by applying multi-dimensional, transient model of all-vanadium redox flow battery (VRFB). Simulation result reveals that large compression leads to greater pressure drop throughout the electrodes, which requires large pumping power to circulate electrolyte while lowered ohmic resistance results in better power capability of the battery. Also, cell compression results in imbalance between anolyte and catholyte and convective crossover of vanadium ions through the separator due to large pressure difference between negative and positive electrodes. Although it is predicted that the battery power is quickly improved due to the reduced ohmic resistance, the capacity decay of the battery is accelerated in the long term operation when the battery cell is compressed. Therefore, it is important to optimize the battery performance by taking trade-off between power and capacity when designing VRFB system.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.60-65
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• 2005

The electrosorption of U(VI) from waste water was carried out by using activated carbon fiber(ACF) felt electrode in a continuous electrosorption cell. In order to enhance the electrosorption capacity at lower potential, ACF felt was chemically modified in acidic, basic and neutral solution. Pore structure and functional groups of chemically modified ACF were examined, and the effect of treatment conditions was studied for the adsorption of U(VI). Specific surface area of all ACFs decreases by this treatment. The amount of acidic functional groups decreases with basic and neutral salt treatment, while the amount increases a lot with acidic treatment. The electrosorption capacity of U(VI) decreases on using the acid treated electrode due to the shielding effect of acidic functional groups. Base treated electrode enhances the capacity due to the reduction of acidic functional groups. The electrosorption amount of U(VI) on the base treated electrode at -0.3 V corresponds to that of ACF electrode at -0.9 V. Such a good adsorption capacity was not only due to the reduction of shielding effect but also the increase of $OH^-$ in the electric double layer on ACF surface by the application of negative potential.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.19-26
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• 2012

SEI (solid electrolyte interphase) layers are generated on a graphite negative electrode from three different electrolytes and low-temperature ($-30^{\circ}C$) charge/discharge performance of the graphite electrode is examined. The electrolytes are prepared by adding 2 wt% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) into a standard electrolyte solution. The charge-discharge capacity of graphite electrode shows the following decreasing order; FEC-added one>standard>VC-added one. The polarization during a constant-current charging shows the reverse order. These observations illustrate that the SEI film resistance and charge transfer resistance differ according to the used additives. This feature has been confirmed by analyzing the chemical composition and thickness of three SEI layers. The SEI layer generated from the standard electrolyte is composed of polymeric carbon-oxygen species and the decomposition products ($Li_xPF_yO_z$) of lithium salt. The VC-derived surface film shows the largest resistance value even if the salt decomposition is not severe due to the presence of dense film comprising C-O species. The FEC-derived SEI layer shows the lowest resistance value as the C-O species are less populated and salt decomposition is not serious. In short, the FEC-added electrolyte generates the SEI layer of the smallest resistance to give the best low-temperature performance for the graphite negative electrode.