• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.325-330
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• 1981

The electrochemical behavior of cadmium electrode for the nickel-cadmium battery system has been studied by cyclic voltammetry, controlled potential electrolysis and X-ray diffraction method. Cathodic polarization curve for cadmium hydroxide electrode prepared by electrochemical pretreatment of metallic cadmium showed two peaks. It has been found that cadmium hydroxide was reduced to cadmium metal at the first peak potential, whereas very activated metal of cadmium which was strongly oriented (002) rather than (101) was formed at the second peak potential. It was also found that the cadmium formed at the second peak potential reacted rapidly with oxygen. Therefore, it could be presumed that the cadmium recombination reaction with the oxygen was chemical, and could be represented as $2Cd + O_2 + 2H_2O\;{\longrightarrow}\;2Cd(OH)_2$.

• 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.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.587-593
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• 2011

A new high power density and low cost Photovoltaic Power Conditioning System (PV PCS) with energy storage system is proposed. Its high power density and cost effectiveness can be achieved through the unification of the maximum power point tracker and battery charger/discharger. Despite of the reduced power stage, the proposed system can achieve the same performances of maximum power point tracking and battery charging/discharging as the conventional system. Moreover, the high voltage stress across the link-capacitor can be relieved through the series-connected link-capacitor with the battery. Therefore, a large number of series/parallel-connected link-capacitors can be reduced by 4-times. Especially, when the utility power failure happens, both photovoltaic and battery energies can be supplied to the load with only one power stage. Therefore, it features a simpler structure, less mass, lower cost, and fewer devices. Finally, to confirm the operation, validity, and features of the proposed system, theoretical analysis and experimental results from a single phase AC 220Vrms/1.5kW prototype are presented.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.1
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• pp.18-26
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• 1973

In AM detection system, when the ratio of the frequency of the carrier to that of the modulating signal becomes less than a ratio of approximately 10:1, AM detectors become unable to detect the impressed signal in a satisfactory waveform. The failure of detecting such a super wide-band AM signal resulting from charging and discharging transient phenomena in associated diode circuit during the detecting of AM signal, has been a cause of limiting the channel capacity in AM or FM super multiplexing systems. This Paper presents the "Poly-phase Envelope Detection System" as a suitable method to solve the problem and the analyses of the system suggested. This system will make it possible to take the envelope out of the impressed AM signal to any desired degree of accuracy even when the ratio of the frequency of the carrier to that of the modulating signal approaches unity. Experiments were carried out to verify the validity of the theory of Poly-phase Envelope Detection System by adopting the frequency conversion method from among the two proposals.proposals.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.35-42
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• 1996

In this paper, a development of model based battery SOC indicator is described. The proposed method is independent upon initial SOC, is reliable on the sudden change of load, and could estimate the available driving distance. The mathematical model of battery which has relation of the current, voltage and SOC estimates the SOC by least square estimation to minimize the error between measured voltage and estimated voltage. For experiment, the charging and discharging system using computer was designed to acquire the current and voltage data for model. The feasibility in electric vehicle was confirmed by variable load testing using the developed SOC indicator by stand-alone type microcontroller.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.328-339
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• 2006

In this paper the characteristic analysis of a single-phase switched reluctance motor (SRM) drive system with power factor correction (PFC) circuit is presented. The SRM is a low cost, simple and has a good high speed performance. The SRM drive with diode rectifier and filter capacitor has a low power factor because of short switch on time of capacitor. A novel switching topologic is presented to improve power factor and reduce torque ripple based on analysis of PFC circuit. Accordingly the SRM drive system with PFC circuit is also presented. Through the numerical analysis of the system, the toque ripple, power factor and efficiency with the change of rotary speed, load torque and capacity of the capacitor are achieved and compared with actual measured value.

• Resources Recycling
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• v.9 no.4
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• pp.37-43
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• 2000

Leaching of $LiCoO_2$ as a cathodic active materials for recovering Li and Co from spent lithium ion battery was investigated in terms of reaction variables. At the optimum condition determined in the previous work, Li and Co in a $H_2SO_4$ and $HNO_3$ solution were dissolved 70~80% and 40%, respectively. Li and Co were leached over 95% with the addition of a reductant such as $Na_2S_2O_3$ or $H_2O_2$. This behavior is probably due to the reduction of $Co^{3+}$ to $Co^{2+}$. Leaching of $LiCoCo_2$ powder obtained by calcination of an electrode materials from spent batteries was also carried out. Leaching efficiency of Li and Co were over 99% at the optimum condition with $H_2O_2$ addition of 1.7 vol.%. It seems to be due to the activation of $LiCoO_2$ by repeated charging and discharging or an imperfect crystal structure by deintercalation of Li.

• Polymer(Korea)
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• v.35 no.6
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• pp.586-592
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• 2011

In this study, we synthesized vinylbenzyl chloride-co-styrene-co hydroxyethyl acrylate (VBC-co-St-co-HEA) copolymer that can be applied to redox the flow battery process. The anion exchange membrane was prepared by the amination and crosslinking of VBC-co-St-co-HEA copolymer. The chemical structure and thermal properties of VBC-co-St-co-HEA copolymer and aminated VBC-co-St-co-HEA(AVSH) membrane were characterized by FTIR, $^1H$ NMR, TGA, and GPC analysis. The membrane properties such as ion exchange capacity(IEC), electrical resistance, ion conductivity and efficiency of all-vanadium redox flow battery were measured. The IEC value, electrical resistance, and ion conductivity were 1.17 meq/g, $1.9{\Omega}{\cdot}cm^2$, 0.009 S/cm, respectively. The charge-discharge efficiency, voltage efficiency and energy efficiency from all-vanadium redox flow battery test were 99.5, 72.6 and 72.1%, respectively.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.139-145
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• 2001

Various compositions of iron oxide based materials as a cathode of lithium secondary battery have been fabricated and tested with electrochemical method. A layered form of $LiFeO_2$ was synthesized by mixing and heating the initial materials of $FeCl_3\;6H_2O,\;LiOH$ and NaOH at low temperature. The effect of changing the precursors composition was investigated. As a result, when increasing the additive amount of NaOH, the capacity of the electrode is decreased but the performance and declining rate of capacity became smaller. $LiFeO_2$ synthesized with the weight ratio of $NaOH/FeCl_3/LiOH,\;2/1/7$ showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles. Charge-discharge tests of lithium cells with $LiFeO_2$ cathode having the layer structure were performed. This cell showed the reversibility in the range of 1.5-4.5V of cell voltage. By using CPR method, chemical diffusion coefficients were measured in 1M $LiPF_6/EC/DEC$ solution. The value of chemical diffusion coefficient decreased with increasing the lithium content x, In 0.5$10^{-11}^cm^2/s$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.15-23
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• 2017

This paper reports a SOC(State-of-Charge) estimation method using the extended Kalman filter(EKF) algorithm, which can allow real-time implementation and reduce the error of the model and be robust against noise, to accurately estimate and evaluate the charging/discharging state of the EV(Electric Vehicle) battery. The battery was modeled as the first order Thevenin model for the EKF algorithm and the parameters were derived through experiments. This paper proposes the changed method, which can have the SOC to 0% ~ 100% regardless of the aging of the battery by replacing the rated capacity specified in the battery with the maximum chargeable capacity. In addition, This paper proposes the EKF algorithm to estimate the non-linearity interval of the battery and simulation result based on Ah-counting shows that the proposed algorithm reduces the estimation error to less than 5% in all intervals of the SOC.