• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.868-873
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• 2019

In this study, the evaluation of performance of AORFB using methyl viologen and TEMPOL as organic active materials in neutral supporting electrolyte (NaCl) with various membrane types was performed. Using methyl viologen and TEMPOL as active materials in neutral electrolyte solution, the cell voltage is 1.37V which is relatively high value for AORFB. Two types of membranes were examined for performance comparison. First, when using Nafion 117 membrane which is commercial cation exchange membrane, only the charge process occurred in the first cycle and the single cell couldn't work because of its high resistance. However, when using Fumasep anion exchange membrane (FAA-3-50) instead of Nafion 117 membrane, the result was obtained as the totally different charge-discharge graphs. When current density was $40mA{\cdot}cm^{-2}$ and cut off voltage range was from 0.55 V to 1.7 V, the charge efficiency (CE) was 97% and voltage efficiency (VE) was 78%. In addition, the discharge capacity was $1.44Ah{\cdot}L^{-1}$ which was 54% of theoretical capacity ($2.68Ah{\cdot}L^{-1}$) at $10^{th}$ cycle and the capacity loss rate was $0.0015Ah{\cdot}L^{-1}$ per cycle during 50 cycles. Through cyclic voltammetry test, it seems that this difference in the performance between the full cell using Nafion 117 membrane and Fumasep anion exchange membrane came from increasing resistance due to chemical reaction between membrane and active material, not the capacity loss due to cross-over of active material through membrane.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.71-77
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• 2014

The performance of catalysts for the recombination of oxyhydrogen gas was measured and compared with the results obtained from theoretical model. The oxyhydrogen gas was generated by the electrolysis cell and recombined through the fixed bed catalytic reactor. The yield that is the ratio of water-amount produced to the water-amount consumed in the electrolysis cell was increased with the increase of KOH concentration in electrolysis cell and the applied current. The catalyst 1 showed the best performance and the yield was under 60 %. The faradic yield calculated by Faraday's law showed about 100% in maximum with catalyst 1. The production rate of water generated by the recombination was 5-40 g/day dependent on the flow rate of mixed gas. Considering the results calculated from the pseudo-homogeneous catalytic reactor model, the hot point inside the reactor was moved to the direction of outlet and the maximum temperatures were $440-480^{\circ}K$ when the gas flow rate increased. The production rate of water calculated from the theoretical model showed good agreement with experimental results below the flow rate of $0.5cm^3/sec$, but there were much differences above that flow rate.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.6-12
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• 2003

Plasma carbon black(PB) which prepared by plasma pyrolysis of methane was treated at 800, 1300 and $2100^{\circ}C$ under $2\times10^{-2}$ torr. Four different samples including raw PB were added to $LiCoO_2$, cathode active material of lithium secondary battery, to investigate effects of properties of plasma black as conductors on electrochemical characteristics. Based on our experimental results, PB conductors with low amount of surface functional groups and high electrical conductivity enhanced the cyclability and the initial discharge capacity. However, deterioration of rate capability and cyclability were observed (or the plasma black treated at $2100^{\circ}C$ For the plasma black conductor prepared from plasma pyrolysis, the effects of properties of carbon black on electrochemical characteristics were combined results of changes in electrical conductivity and structural properties such as agglomeration of plasma black. The conductivity of plasma black increased with treatment temperature, while dispersion of plasma black decreased. As a result, the high cyclability of cell was observed at $800^{\circ}C$ of heat treatment temperature.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.639-645
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• 2020

Among the components of redox flow battery (RFB), the electrode serves as a diffusion layer of an electrolyte and a path for electrons and also is a major component that directly affects the RFB performance. In this paper, chloric/sulfuric mixed acidwas used as a supporting electrolyte in RFB system with Fe2+/Fe3+ and V2+/V3+ as redox couple. The optimum electrode and activation temperature were suggested by comparing the capacity, coulombic efficiency and energy efficiency according to the electrode type and activation temperature. In the RFB single cell evaluation using 5 types of carbon electrodes used in the experiments, all of them showed close to the theoretical capacity to retain the reliability of the evaluation results. GFD4EA showed relatively excellent energy efficiency and charge/discharge capacity. In order to investigate the electrochemical performance according to the activation temperature, GFD4EA electrode was activated by heat treatment at different temperatures of 400, 450, 500, 600 and 700 ℃ under an air atmosphere. Changes in physical properties before and after the activation were observed using electrode mass retention, scanning electron microscope (SEM), XPS analysis, and electrochemical performance was compared by conducting RFB single evaluation using electrodes activated at each temperature given above.

• Journal of the Korean Electrochemical Society
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• v.19 no.4
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• pp.123-128
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• 2016

In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP)-based gel polymer electrolyte incorporating nano-size $Al_2O_3$ ceramic particle was prepared by electrospinning. The gel polymer electrolyte (GPE) incorporated with $Al_2O_3$ ceramic particle showed higher ionic conductivity of $9.5{\times}10^{-2}Scm^{-1}$ than pure PVdF-HFP GPE without ceramic particle and improved the electrochemical stability up to 5.2 V. The GPEs were assembled with $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ (NMC) cathode for electrochemical test. The GPE batteries at 0.1 C-rate delivered $168.2mAh\;g^{-1}$ for pure GPE and $189.6mAh\;g^{-1}$ for hybrid GPE, respectively. Therefore, the incorporation of high dielectric constant ceramic particle will be good strategy to enhance the stability and electrochemical properties of lithium ion gel polymer batteries.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.95-99
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• 2017

The lifetime of a battery that supplies all the power required by a satellite in the eclipse is directly related to the lifetime of the satellite. Because the lifetime of the battery is influenced by the charging method of the battery, the power control unit that controls the charging of the battery should be designed in consideration of battery life. The battery charging is performed by controlling the charge current in the power control unit generated from the solar cell in the daytime. In order to prevent overcharge of the battery and for considering frequency of eclipse in each season, parameters related battery charging should be designed differently according to the season and to prevent over-current charging and over-voltage charging during charging, charge current is controlled by monitoring battery charge / discharge status, charge current amount, battery voltage, battery capacity, battery temperature and battery cell voltage. In satellite, tapering method is used to control charge current by reflecting each condition. In this paper, design battery charging algorithm of satellite power control unit using tapering charging method. convert the designed algorithm into a code that can be uploaded to satellites and verify the operation through testing in the established satellite environment.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.10-14
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• 2011

The electrode material performances of electric double layer capacitor(EDLC) were investigated using mesopous active carbon fiber(ACF), which was prepared by the iron exchange method. The mesoporous ACF had pore characteristics of specific surface area around 1249, 664 $m^2$/g, mesoporous fraction around 70.6-81.3% and meanpore size around 2.78-4.14 nm. The results showed that as HNO3 treatment time decreased, the specific surface area increased and mesoporous fraction decreased. To investigate electrochemical performance of EDLC, unit cell was manufactured using mesoporus ACF, conducting material and binder; organic elctrolyte was used on this experiment. The specific capacitance of ACF treated with HNO3 for 2 hours turned out to be 0.47 $F/cm^2$and the results of the cyclic charge-discharge tests were stable. Thus, the electrochemical performance of EDLC was mainly dependent on specific surface area of ACF electrode and the diffusion resistance of charge decreased as the mesopore increased.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1114-1118
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• 1999

Barrier rib for the plasma display panel(PDP) was made by photolithographic process utilizing photosensitive barrier rib paste. The barrier rib paste was prepared by first dissolving ethylcellulose(binder polymer) in butyl carbitol(BC)/butyl carbitol acetate(BCA) =30/70 wt % mixture solvent at 15 wt % concentration. To this solution a mixture of functional monomers consisted of tripropyleneglycol diacrylate/ pentaerythritol triacrylate = 50/50 wt %, Irgacur 651 photoinitiator, and barrier rib powder were added and then the whole mixture was mixed in the three roll mill for 2 hr. The effect of component and concentration of photosensitive barrier paste on the photolithographic process was studied. After optimization of the paste formulation and photolithographic process, barrier rib could be obtained with good resolution up to $100{\mu}m$ height.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.592-597
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• 2014

The graphite/$SiO_2$ composites as anode materials for lithium-ion batteries were prepared by sol-gel method to improve the graphite's electrochemical characteristics. The prepared graphite/$SiO_2$ composites were analysed by XRD, FE-SEM and EDX. The graphite surface modified by silicon dioxide showed several advantages to stabilize SEI layer. The electrochemical characteristics were investigated for lithium ion battery using graphite/$SiO_2$ as the working electrode and Li metal as the counter electrode. Electrochemical behaviors using organic electrolytes ($LiPF_6$, EC/DMC) were characterized by charge/discharge, cycle, cyclic voltammetry and impedance tests. The lithium ion battery using graphite/$SiO_2$ electrodes had better capacity than that of using graphite electrodes and was able to deliver a discharge capacity with 475 mAh/g at a rate of 0.1 C. Also, the capacity retention ratio of the modified graphite reaches 99% at a rate of 0.8 C.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.131-136
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• 2015

The nanostructural graphene/vanadium oxide (graphene/$V_2O_5$) composite with enhanced capacitance was synthesized by the electro-deposition in 0.5 M $VOSO_4$ solution. The morphology of composites was characterized using scanning electron microscopy (SEM), x-ray diffraction pattern (XRD), and x-ray photoelectron spectroscopy (XPS). The oxidation states of the electro-deposited vanadium oxide was found to be $V^{5+}$ and $V^{4+}$. The morphology of the prepared graphene/$V_2O_5$ composite exhibits a netlike nano-structure with $V_2O_5$ nanorods in about 100 nm diameter, which could lead a better contact between electrolyte an electrode. The composite with a deposition time of 4,000 s exhibits the specific capacitance of $854mF/cm^2$ at a scan rate of 20 mV/s and the capacitance retention of 53% after 1000 CV cycles.