• Elastomers and Composites
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• v.39 no.3
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• pp.179-185
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• 2004

Frequency dependency or electrical property stabilization during vulcanization of modified NR/IR composite materials was studied using in-situ electrical property measuring technique. Volume resistivity(p) before and after vulcanization reaction of the sample was measured as the function or frequency in the range or 1Hz to 10kHz at reaction temperatures of 130, 140, 150, and $160^{\circ}C$, respectively. A double stabilization mode of frequency dependency was observed, in which a slow stabilization process of p to a value of ca. $1.0{\times}10^7\;{\Omega}-cm$ occurred after a drastic initial decrease from ca. $9.0{\times}10^7\;{\Omega}-cm$. In addition, notable temperature dependencies of p values were also observed before and after vulcanization reaction, that is, p values at 130 and $140^{\circ}C$ after vulcanization were observed as about 1/3 of those values before vulcanization. All the observed facts were considered as the results from the interaction between the electrode and the bulk sample materials, i.e., electronic charge-discharge, and from the structure change of samples including CB rearrangement by the vulcanization.

• Journal of the Korean Chemical Society
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• v.66 no.6
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• pp.451-458
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• 2022

Through the crystal alignment research based on the magnetic properties of LiNi_xMn_yCo_1-(x+y)O₂ such as magnetic susceptibility and related anisotropy, a crystal aligned LiNi_0.6Mn_0.2Co_0.2O₂ electrode is obtained, in which the (00l) plane is frequently oriented perpendicular to the surface of a current collector. The crystal aligned LiNi_0.6Mn_0.2Co_0.2O₂ electrode steadily exhibits low electrode polarization properties during the charge/discharge process in a lithium-ion battery, thus affording an improved capacity compared to a pristine LiNi_0.6Mn_0.2Co_0.2O₂ electrode. The aligned LiNi_0.6Mn_0.2Co_0.2O₂ electrode may have an appropriate structural nature for fast lithium-ion transport due to the oriented (00l) plane, and thus it contributes to enhancing the battery performance. This enhancement is analyzed in terms of various electrochemical theories and experiment results; thus, it is verified to occur because of the considerably fast lithium-ion transport in the aligned LiNi_0.6Mn_0.2Co_0.2O₂ electrode.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.309-315
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• 2024

Silicon and carbon composite (SiC) is considered one of the most promising anode materials for the commercialization of Si-based anodes, as it could simultaneously satisfy the high theoretical capacity of Si and the high electronic conductivity of carbon. However, SiC active material undergoes repeated volumetric changes during charge/discharge processes, leading to continuous electrolyte decomposition and capacity fading, which is still considered an issue that needs to be addressed. To solve this issue, we suggest a 4,4'-Methylenebis(cyclohexyl isocyanate) (H₁₂MDI)-based waterborne polyurethane binder (HPUD), which forms a 3D network structure through thermal cross-linking reaction. The cross-linked HPUD (denoted as CHPU) was prepared using an epoxy ring-opening reaction of the cross-linker, triglycidyl isocyanurate (TGIC), via simple thermal treatment during the SiC anode drying process. The SiC anode with the CHPU binder, which exhibited superior mechanical and adhesion properties, not only demonstrated excellent rate and cycling performance but also alleviated the volume expansion of the SiC anode. This work implies that eco-friendly binders with cross-linked structures could be utilized for various Si-based anodes.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.209-213
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• 2019

Recently, demand for high energy density and long cycling stability of energy storage system has increased for application using with frequency regulation (F/R) in power grid. Supercapacitor have long lifetime and high charge and discharge rate, it is very adaptable to apply a frequency regulation in power grid. Supercapacitor can complement batteries to reduce the size and installation of batteries. Because their utilization in a system can potentially eliminate the need for short-term frequent replacement as required by batteries, hence, saving the resources invested in the upkeep of the whole system or extension of lifecycle of batteries in the long run of power grid. However, low energy density in supercapacitor is critical weakness to utilization for huge energy storage system of power grid. So, it is still far from being able to replace batteries and struggle in meeting the demand for a high energy density. But, today, LIC (Lithium Ion Capacitor) considered as an attractive structure to improve energy density much more than EDLC (Electric double layer capacitor) because LIC has high voltage range up to 3.8 V. But, many aspects of the electrochemical performance of LIC still need to be examined closely in order to apply for commercial use. In this study, in order to improve the capacitance of LIC related with energy density, we designed new method of pre-doping in anode electrode. The electrode in cathode were fabricated in dry room which has a relative humidity under 0.1% and constant electrode thickness over $100{\mu}m$ was manufactured for stable mechanical strength and anode doping. To minimize of contact resistance, fabricated electrode was conducted hot compression process from room temperature to $65^{\circ}C$. We designed various pre-doping method for LIC structure and analyzing the doping mechanism issues. Finally, we suggest new pre-doping method to improve the capacitance and electrochemical stability for LIC.