• Journal of the Korean Chemical Society
• /
• v.43 no.2
• /
• pp.199-205
• /
• 1999

The electrochemical properties of PAN-PVDF-PEGME blend polymer electrolyte system are investigated and the physical properties are also measured with varying the content of PEGME. This PEGME partially reduces the crystallinity of PVDF. The ionic conductivities of the polymer electrolytes are about $10^{-3}S/cm$, which may be applicable to a constituent of lithium secondary battery. From the temperature dependence of ionic conductivity, it is suggested that the ionic conductivity increases with the PEGME content due to the fomation of effective ion-conducting path. The cation transference number reaches its maximum value for the electrolytes (SPE 2) with 10 wt% PEGME and then decreases for further increase of PEGME contnet. The electrochemically stable range of SPE 1 (without PEGME) is about 4.3 V, but SPE 2-4 (PAN-PVDF-PEGME system) is about 4.6 V. When these polymer electrolyte are used as electrolyte in rechargeable battery and the cell performances are tested, the discharge capacity increses with the amount of PEGME. Therefore, PEGME increases the ionic conductivity, extends the electrochemical stable range, and finally improves the discharge capacity of cell adopting the electrolyte system.

• Journal of the Korean Electrochemical Society
• /
• v.17 no.1
• /
• pp.65-70
• /
• 2014

In this study, crosslinked poly(POEM-co-AMPSLi-co-GMA)s were prepared by epoxy coupling of GMA after radical copolymerization of AMPS, POEM and GMA followed by acid-base titration reaction between sulfonic acid of AMPS and $Li_2CO_3$. It was observed that the crystalline melting temperature of POEM was effected by mol% of components and shifted to lower value by lithiation of AMPS group. The ionic conductivity of crosslinked polymer electrolyte was decreased by addition of GMA but maintained over $1.0{\times}10^{-6}S\;cm^{-1}$ until 16 mol%. Particularly, the self-doped polymer electrolyte with 2 mol% of GMA showed its ionic conductivity as high as $4.08{\times}10^{-6}S\;cm^{-1}$ at room temperature and electrochemical stability up to 6 V. In addition, 0.11 MPa of modulus and 270% of elongation were obtained from the free standing film of crosslinked polymer electrolyte.

• Journal of the Korean Electrochemical Society
• /
• v.16 no.4
• /
• pp.198-203
• /
• 2013

Copolymer consisted of MMA and tBMA was synthesized by radical polymerization and poly(MMA-co-MA) was prepared by selective hydrolysis of tert-butyl group. The obtained polymer was coupled with epoxy functionalized PEO of various molecular weight to synthesize poly(MMA-co-PEGMA) with different side chain length. The AC-impedance measurement shows $1.88{\times}10^{-6}Scm^{-1}$ of room temperature ionic conductivity from 48mol% of MMA while $5.11{\times}10^{-8}Scm^{-1}$ was observed in 82mol% sample. In addition, there was an effect of PEGMA molecular weight on ionic conductivity possibly due to the steric hindrance in grafting-onto coupling reaction. Finally, the polymer electrolytes shows electrochemical stability up to 6V at room temperature.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.587-596
• /
• 2021

Naval battleships have systems to perform special purposes, such as the Command and Fire Control System (CFCS). Some of the this equipment should be equipped with an Uninterruptible Power System (UPS ) to ensure operational continuity and the backup of important data, even during unexpected power outages caused by problems with the ship's power generator. Heavy combat losses can occur if the equipment cannot satisfy the function. Therefore, it is important to design a stable UPS. The battery and Battery Management System (BMS) are two of the most important factors for designing a stable UPS. A power outage will be encountered if the battery and BMS are not stable. The customer will be exposed to abnormal situations, loss of important tactical data, and inability to operate some of the CFCS. As a result, an enhanced safety system should be designed. Thus, this study implemented and verified the improved system in terms of three methods, such as comparative analysis of the batteries, improvement about leakage current of the circuit, and tests of the aggressive environmental resistance to improve the UPS for CFCS.

• Electronic Materials Letters
• /
• v.14 no.6
• /
• pp.755-765
• /
• 2018

In situ nitrogen doped hard carbon nanotubes (NHCNT) were fabricated by pyrolyzing tubular nitrogen doped conjugated microporous polymer. KOH activated NHCNT (K-NHCNT) were also prepared to improve their porous structure. XRD, SEM, TEM, EDS, XPS, Raman spectra, $N_2$ adsorption-desorption, galvanostatic charging-discharge, cyclic voltammetry and EIS were used to characterize the structure and performance of NHCNT and K-NHCNT. XRD and Raman spectra reveal K-NHCNT own a more disorder carbon. SEM indicate that the diameters of K-NHCNT are smaller than that of NHCNT. TEM and EDS further indicate that K-NHCNT are hollow carbon nanotubes with nitrogen uniformly distributed. $N_2$ adsorption-desorption analysis reveals that K-NHCNT have an ultra high specific surface area of $1787.37m^2g^{-1}$, which is much larger than that of NHCNT ($531.98m^2g^{-1}$). K-NHCNT delivers a high reversible capacity of $918mAh\;g^{-1}$ at $0.6A\;g^{-1}$. Even after 350 times cycling, the capacity of K-NHCNT cycled after 350 cycles at $0.6A\;g^{-1}$ is still as high as $591.6mAh\;g^{-1}$. Such outstanding electrochemical performance of the K-NHCNT are clearly attributed by its superior characters, which have great advantages over those commercial available carbon nanotubes ($200-450mAh\;g^{-1}$) not only for its desired electrochemical performance but also for its easily and scaling-up preparation.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.3
• /
• pp.262-271
• /
• 2023

For electrode stability and the electrochemical performance of the Li-ion cell, it is essential that the active ingredients and unique additives in the polymer binder be well dispersed with the solvent-based slurry. The efficient procedure used to create the slurry affects the rheological characteristics of the electrode slurry. When successively adding different steps of Nmethyl-2-pyrrolidone (NMP) solvent to the cathode composition, it is evenly disseminated. The electrochemical performance of the Li-ion cells and the electrodes made with slurry formed by single step and multiple steps of addition of NMP solvent are examined. To preform rheological properties of cathode electrode slurry on Ni-rich Lithium Nickel-Cobalt-Aluminum Oxide (LiNi_0.80Co_0.15Al_0.05) (NCA). Also, we investigate different step addition of electrode formation and mechanical strength characterization like peel strength. According to the EIS study, a multi-step electrode slurry has lower internal resistance than a single-step electrode slurry, which results in better electrical characteristics and efficiency. Further, microstructure of electrodes is obtained electrochemical performance in the 18650 cylindrical cells with targeted capacity of 1.5 Ah. The slurry of electrodes prepared by single step and multiple steps of addition of NMP solvent and its effect on the fabrication of 1.5 Ah cells. A three-step solvent addition on slurry has been found to be a lower internal resistance than a single-step electrode slurry as confirmed by the EIS analysis, yielding improved electrical properties and efficiency.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.10
• /
• pp.82-92
• /
• 2005

The present study was carried out in order to develop a remote-controlled micro ornithopter with a weight of 20 gram. This ornithopter has three channel radio control. It runs on two direct-current type pager motors powered by a lithium polymer battery which flaps its 35cm wings. The performance of an ornithopter, applied to a flapping motion only, was validated by flight tests. The flight test results indicate that the ornithopter developed here has sufficient thrust to propel itself.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.7
• /
• pp.881-887
• /
• 2016

In this study, the vibration-based tactile actuator for smart wear applications is presented by using piezoelectric ceramic transducers. The compact wireless actuation system is constructed with a high voltage piezoelectric amplifier, a microcontroller, wireless communication module, and rechargeable lithium-polymer battery. For the wireless communication between a hardware and an operator, the bluetooth-based wireless communication system is prepared and the user interface is provided via smart phone applications. From a series of experimental user studies, it is demonstrated that the proposed vibro-tactile actuator based on piezoelectric ceramic transducers can be effectively applied to smart wear applications.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.2
• /
• pp.131-138
• /
• 2019

To improve the performance of Si anodes in advanced Li-ion batteries, the design of the electrode plays a critical role, especially due to the large volumetric expansion in the Si anode during Li insertion. In our study, we used a simple fabrication method to prepare Si-based electrodes by grafting polyacrylic acid (PAA) to a carboxymethyl cellulose (CMC) binder (CMC-g-PAA). The procedure consists of first mixing nano-sized Si and the binders (CMC and PAA), and then coating the slurry on a Cu foil. The carbon network was formed via carbonization of the binders i.e., by a simple heat treatment of the electrode. The carbon network in the electrode is mechanically and electrically robust, which leads to higher electrical conductivity and better mechanical property. This explains its long cycle performance without the addition of a conducting agent (for example, carbon). Therefore, the partially carbonized CMC-g-PAA binder presented in this study represents a new feasible approach to produce Si anodes for use in advanced Li-ion batteries.

• Journal of the Korean Electrochemical Society
• /
• v.17 no.4
• /
• pp.222-228
• /
• 2014

Ni-rich system $Li[Ni_{1-x-y}Co_xMn_y]O_2$ of lithium secondary battery cathode material keep a high discharge capacity. However, by the Ni content increases, there is a problem that the electrochemical properties and stability of the structure are reduced. In order to solve these problems, research for positive ion doping is performed. The one of the cathode material, barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01), was synthesized by the precursor, $Ni_{0.6}Co_{0.1}Mn_{0.3}(OH)_2$, from the co-precipitation method. The barium doped materials have studied the structural and electrochemical properties. The analysis of structural properties, results of X-ray diffraction analysis, and those results confirmed the change of the lattice from the binding energy in the structure by barium doping. Increased stability of the layered structure was observed by $I_{(006)}+I_{(102)}/I_{(101)}$(R-factor) ratio decrease. we expected that the electrochemical characteristics are improved. 23 mAh/g discharge capacity of barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01) electrode is higher than discharge capacity of $Li[Ni_{0.6}Co_{0.1}Mn_{0.3}]O_2$ due to decrease overvoltage. And, through the structural stability was confirmed that improved the cycle characteristics. We caused a reduction in charge transfer resistance between the electrolyte and the electrode was confirmed that the C-rate characteristics are improved.