Mun-Soo Yun

Chemical polymerization of 2-chloroaniline and 2-fluoroaniline by chromic acid

Abstract The chemical polymerization of 2-chloroaniline and 2-fluoroaniline was carried out by oxidants containing chrome in some solvents. The best result was obtained by chromic acid in H 2 O where the oxidizing power of oxidant is largely enhanced by HCl. Some characteristics of synthesized polymers were examined by ESR and FTIR measurement.

Electrochemical performances of gel polymer electrolytes using tetra(ethylene glycol) diacrylate

Abstract A gel polymer electrolyte (GPE) was prepared using tetra(ethylene glycol) diacrylate monomer, benzoyl peroxide, and 1.0 M LiPF 6 / EC-DEC ( 1 : 1 vol % ). The LiCoO 2 /GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures. The viscosity of the precursor containing the 5 vol % tetra(ethylene glycol) diacrylate monomer was around 4.6 mPa s . The ionic conductivity of the gel polymer electrolyte at 20°C was around 5.9×10 −3 S cm −1 . The gel polymer electrolyte had good electrochemical stability up to 4.3 V vs. Li/Li + . The capacity of the LiCoO 2 /GPE/graphite cell at 2.0 C rate was 63% of the discharge capacity at 0.2 C rate. The capacity of the cell at −10°C was 81% of the discharge capacity at 20°C. Discharge capacity of the cell with gel polymer electrolyte was stable with charge–discharge cycling.

A study on carbon coating to silicon and electrochemical characteristics of Si-C/Li cells

The aim of this paper is to study the electrochemical behavior of Si-C material synthesized by heating a mixture of silicon and polyvinylidene fluoride (PVDF) in the ratios of 5, 20, and 50 wt%. The particle size of the synthesized material was found to be increased with increase in the PVDF ratio. The coexistence of silicon with carbon was confirmed from the XRD analysis. A field emission scanning electron microscope (FESEM) study performed with the material proved the improvement in coating efficiency with increase in the PVDF ratio. Coin cells of the type 2025 were made by using the synthesized material, and the electrochemical properties were studied. An electrode was prepared by using the developed Si-C material. Si-C|Li cells were made with this electrode. A charge|discharge test was performed for 20 cycles at 0.1 C hour rate. Initial charge and discharge capacities of Si-C material derived from 20 wt% of PVDF was found to be 1,830 and 526 mAh|g, respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216mAh/g at Si-C material derived from 20 wt% of PVDF, initial intercalation efficiency (IIE), intercalation efficiency at initial charge/discharge, was 68%. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm * g.

A preliminary investigation upon the electrochemical behavior of CoO and NiO anodes: Comparative study

Among the variety of alternate anode materials being studied, the research on the exploration of 3d-metal oxide anodes gains paramount importance in the recent time, as it is bestowed with an easy preparation method and a less complicated decomposition mechanism. Towards this direction, an attempt to synthesize the compound CoO and to investigate the electrochemical behavior of the same both individually and in comparison with NiO compounds was made with a view to understand the extent to which the chosen candidates, viz., CoO and NiO can be exploited as high capacity anodes. Between the two oxides, CoO exhibited a specific capacity of at least 550 mAh/g, against NiO with an average capacity of ∼330 mAh/g. Also, the magnitude of irreversible capacity loss and the extent of capacity fade upon cycling corresponding to CoO anode were found to be lesser than NiO anodes. The enhanced specific capacity values and the better cycleability properties of CoO anodes are believed to be due to the inherent electrochemical characteristics of the compound. The type and the nature of SEI formed over the electrode surface and the formation of possible progressive agglomeration of the products of decomposition are expected to be the factors responsible for the difference in the electrochemical behavior of CoO and NiO anodes. In short, electrochemical characterization of the individual oxides are studied and probable reasons for the observed difference in the charge-discharge behavior of CoO and NiO anodes are discussed in this communication.

Characterization of TiS2 composite cathodes with solid polymer electrolyte

Abstract A TiS 2 composite cathode for lithium polymer battery was developed. We investigated the a.c. impedance response as a function of temperature and charge/discharge cycling process and charge/discharge characteristics of TiS 2 composite/solid polymer electrolyte/Li cells. The passivation layer resistance of the Li/solid polymer electrolyte interface at 25 °C was 292 Ω cm 2 . The total resistance of the TiS 2 bulk and the TiS 2 /solid polymer electrolyte interfaces was 96 Ω cm 2 . The cell resistance significantly decreased at 60 °C. The discharge capacity of the TiS 2 composite cathode with 40 wt.% solid polymer electrolyte was 173 and 146 mAh/g based on TiS 2 at cycle nos. 1 and 20 at 25 °C, respectively. The utilization TiS 2 at the discharge processes nos. 1 and 20 at 25 °C were 72 and 61%, respectively. TiS 2 composite cathode with 40 wt.% solid polymer electrolyte showed better capacity with cycling.

Application of carbon to anode material for the lithium secondary battery

Summary form only given. We have studied on the electrochemical characteristics of carbon materials(petroleum coke, pyrolyzed furan resin(PFR), graphitized mesocarbon microbeads(MCMB), etc.) as anode material of the lithium secondary battery by cyclic voltammetry and galvanostatic charge/discharge with current density and electrolyte. The carbon electrodes were prepared by the coating the slurry of carbon of 90wt% and polyvinylidene fluoride of lOwt% as the binder on Cu foil. During cyclic voltammetry, PFR and MCNM shows good cycling behavior in the condition of scan rate of 10mV/sec, potential range between 0V and 3V vs. Li/Li/sup +/ in IM LiAsF/sub 6//PC electrolytic solution. In the case of galvanostatic charge/discharge of PFR and MCNM, LiAsF/sub 6///PC electrolytic solution was best of all electrolytic solutions tested in the condition of current density of 1mA/cm/sup 2/ and potential range between 0V and 1.5V vs. Li/Li/sup +/. And its electrochemical properties were better in current density of 2mA/cm/sup 2/ than in current density of 1mA/cm/sup 2/. At current density of 2mA/cm/sup 2/, PFR electrode showed ca. 100% Ah efficiency and stable utilization behavior with cycling. The utilization was 25% at the 50th cycle.

Effects of PTFE Contents on Characteristics of Cathode for Zn Air Batteries

Zinc Air batteries obtain their energy density by utilizing ambient oxygen as the cathode materials. And specific capacity of zinc powder is as high as 820 mAh/g. When Zinc Air battery discharged at low current, then discharge voltage profile has very flat pattern until reach to end of voltage. But, when Zinc Air battery discharged at high current, then discharge voltage and energy becomes very low. So we focused on resistance and porosity of cathode with contents of PTFE. Wf studied on the effects of PTFE on performance of Zinc Air batteries. So we have got optimum contents of PTFE binder.

Synthesis of Cross-Linked Polyurethane-Based Gel Polymer Electrolyte and Its Electrochemical Properties

Urethane acrylate oligomer was synthesized and used in a gel polymer electrolyte (GPE) and then its electrochemical performances were evaluated. cells were prepared and their performances depending on discharge currents and temperatures were evaluated. The precursor containing curable mixture had a low viscosity relatively. ionic conductivity of the gel polymer electrolyte at room temperature and was ca. , respectively. GPE showed good electrochemical stability up to potential of 4.5V vs. cell showed a good high-rate and low-temperature performance.

Interface phenomena of organic semiconductor junctioned with metal and inorganic semiconductor

Abstract We have studied on the junction characteristics of organic semiconductor-metal and organic semiconductor — inorganic semiconductor devices. Organic semiconductor was electro-polymerized on metal electrode by constant current method. Considering the formation of oxide layer at the interface in manufacturing process and high resistance of organic semiconductor, we can deduce them as a MIS structure. Usually, it was known that organic semiconductor have rectifying contact with low workfunction metal and ohmic contact with high workfunction metal. But by our experimental results, junction characteristics depend on metal oxide layer rather than workfunction of metals. This oxide layer largely depends on manufacturing process of devices. So we studied the effect of an electro-polymerization condition, film thickness, and doping density in junction characteristics. Also we investigated the solar energy conversion characteristics of these devices. Photon have to be reached near the depletion region to increase the conversion efficiency. We studied on the transparent inorganic semiconductor like CdS as a window material and interface phenomena.

Effect of the Conducting Agent on Characteristics of Cathode for Zn/Air Batteries

아연공기전지는 공기중의 산소를 사용하므로 cathode의 재활용이 가능하다는 장점이 있으며 아연의 이론용량이 820(mAh/g)으로 상당히 높다. 그러나, 아연공기전지는 cathodf치 기공이 너무 작으면 외부로부터 유입되는 산소량이 부족하여 전지의 방전전압이 낮아지는 결과를 초래하게 되며 cathode에 포함되어 있는 도전재의 함량에 따라 저항 및 기공율에 많은 변화를 보이고 있다. 이에 본 연구에서는 전지의 용량, 출력특성, 방전전압, DC저항, ASTM에 의한 기공율 측정을 통해 도전재의 종류 및 함량이 아연공기전지에 미치는 영향을 연구하였으며, Super P의 도전재를