• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.363-368
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• 2018

Polyoxometalates (POMs) have outstanding properties and a great deal of potential for electrochemical applications. As POMs are highly soluble, the implementation of POMs in various functional materials is required to fully use their potential in electrochemical devices. Here, we will review the recently developed immobilization methods to incorporate POMs into conductive nanomaterials, such as nanocarbons and conducting polymers. Various immobilization strategies involve POMs entrapped in conducting polymer matrix and integration of POMs into nanocarbons using a Langmuir-Blodgett technique, a layer-by-layer self-assembly, and an electrochemical in-situ polymerization. In addition, we will review a variety of electrochemical applications including electrocatalysts for water oxidation, lithium-ion batteries, supercapacitors, and electrochemical biosensors.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.2
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• pp.5-15
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• 2022

In this study, heated tobacco biomass was prepared as an active material for supercapacitor device. Retrieved tobacco leaf from the heated tobacco was carbonized at various temperature(800/850/950℃). Carbonized tobacco leaf material synthesized at 850℃ exhibited the highest C/O ratio, indicating the finest carbon quality. In addition, polypyrrole was coated onto the carbonized leaf material for increasing the electrochemical performance via low-temperature polymerization method. As-synthesized carbonized leaf material at 850℃(CTL-850)-based electrode and polypyrrole-coated carbonized leaf material(CTL-850/PPy)-based electrode displayed outstanding specific capacitances of 100.2 and 155.3F g^-1 at 1 A g^-1 with opertaing window of -1.0V and 1.0V. Asymmetric supercapacitor device, assembled with CTL-850 as the negative electrode and CTL-850/PPy as the positive electrode, manifested specific capacitance of 31.1F g^-1(@1 A g^-1) with widened operating voltage window of 2.0V. Moreover, as-prepared asymmetric supercapacitor device was able to lighten up the RED Led (1.8V), suggesting the high capacitance and extension of operating voltage window. The result of this research may help to pave the new possibility toward preparing the effective energy storage device material recycling the biomass.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.3
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• pp.188-196
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• 2009

Due to its high power density, long cycle life and clean nature supercapacitors are widely used for improving the dynamic characteristics of the new and renewable energy sources and extending the battery run-time and life. In this paper improved dynamic model of the supercapacitor is developed by the electrochemical impedance spectroscopy technique. The developed model can be used to accurately estimate the dynamic behaviour of the supercapacitor and calculate the exact capacitance value at a certain state of charges. The model of the supercapacitor in the frequency domain is equivalently transformed into that in the time domain for Matlab/Simulink simulaton. The simulation data shows fine agreements with experimental results, thereby proving the validity and the accuracy of the developed model.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.1
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• pp.43-48
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• 2019

This study investigates the electrochemical characteristics of the hybrid cell that combined the advantageous characteristics of Li secondary battery and supercapacitor, high energy density and high power density, respectively. Electrochemical behaviors of the hybrid cell was characterized by charge/discharge, cycle and impedance tests. The hybrid cell using Li secondary battery and supercapacitor had better discharge capacity and cycle performance than that of using Li secondary battery only. Proper design of such a hybrid cell system is expected to result in substantial benefits to the well being of the Li secondary battery. The hybrid cell involving Li secondary battery for high energy density and supercapacitor for high power density may be the possible solution for future energy storage system.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.57-68
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• 2023

In this study, coffee waste was recycled into nitrogen-doped porous carbon fibers as an active material for high-energy EDLC (Electric Double Layer Capacitors). The coffee waste was mixed with polyvinylpyrrolidone and dissolved into dimethylformamide. The mixture was then electrospun to fabricate coffee waste-derived nanofibers (Bare-CWNF), and carbonization process was followed under a nitrogen atmosphere at 900℃. Similar to Bare-CWNF, the as-synthesized carbonized coffee waste-derived nanofibers (Carbonized-CWNF) maintained its fibrous form while preserving the composition of nitrogen. The electrochemical performance was analyzed for carbonized coffee waste (Carbonized-CW)-, carbonized PAN-derived nanofibers (Carbonized-PNF)-, and Carbonized-CWNF-based electrodes in the operating voltage window of -1.0-0.0V, Among the electrodes, Carbonized-CWNF-based electrodes exhibited the highest specific capacitance of 123.8F g^-1 at 1A g^-1 owing to presence of nitrogen and porous structure. As a result, nitrogen-contained porous carbon fibers synthesized from coffee waste showed excellent electrochemical performance as electrodes for high-energy EDLC. The experimental designed in this study successfully demonstrated the recycling of the coffee waste, one of the plant-based biomass that causes the environmental pollution into high-energy materials, also, attaining the ecofriendliness.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.164-164
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• 2014

Characteristics of electrolyte are those; electrical stability, ion conductivity, viscosity, high temperature work, cell application. Theoretically, GBL has high oxidation voltage. Also, boiling point of GBL is $206^{\circ}C$ and flash point is over $280^{\circ}C$.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.421-426
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• 2016

In this report, polyoxometalte (POM)-doped polypyrrole (Ppy) was deposited on surface of three-dimensional carbon cloth (CC) using an electrodeposition method and its pseudocapacitive behavior was investigated using cyclic voltammetry and galvanostatic charge-discharge. The POM-Ppy coating was thin and conformal which can be controlled by electrodeposition time. As-prepared POM-Ppy/CC was characterized using scanning electron microscope and energy-dispersive X-ray spectroscopy. The unique 3D nanocomposite structure of POM-Ppy/CC was capable of delivering excellent charge storage performances: a high areal capacitance ($561mF/cm^2$), a high rate capability (85%), and a good cycling performance (97% retention).

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1199-1205
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• 2017

Global energy consumption is rapidly increasing yearly due to drastic industrial advances, requiring the development of new energy storage devices. For this reason, supercapacitors with fast charge-discharge, long life cycle and high power density is getting attention, and have been considered as one of the potential energy storage systems. In this research, we developed a supercapacitor that consists of amorphous manganese oxide($MnO_2$) electrodes deposited onto carbon cloth substrates using the hydrothermal method. The Fe-doped amorphous $MnO_2$ samples were characterized by X-ray diffraction(XRD), Energy Dispersive X-ray spectroscopy(EDX), as well as scanning electron microscopy(SEM). The electrochemical analysis of the prepared samples were performed using cyclic voltammetry and galvanostatic charge-discharge measurements in 1M $Na_2SO_4$ electrolyte. The test results demonstrate that the supercapacitor based on the Fe-doped amorphous $MnO_2$ electrodes has a specific capacitance as high as 163F/g at 1A/g current density, and good cycling stability of 87.34% capacitance retention up to 1000 cycles.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.95.1-95.1
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• 2011

In this work, graphene was prepared by modified Hummers method and prepared graphene was applied to electrode materials for supercapacitor. In addition, to enhance the electrochemical performance of graphene, carbon black was deposited onto graphene via chemical reduction. The effect of the carbon black content incorporated on the electrochemical properties of the graphene-based electrodes was investigated. It was found that nano-scaled carbon black aggregates were deposited and dispersed onto the graphene by the chemical reduction of acid treated carbon black and graphite oxide. From the cyclic voltammograms, carbon black-deposited graphene (CB-GR) showed improved electrochemical performance, i.e., current density, quicker response, and better specific capacitance than that of pristine graphene. This indicates that the carbon black deposited onto graphene served as an conductive materials between graphene layers, leading to reducing the contact resistance of graphene and resulted in the increase of the charge transfer between graphene layers by bridge effect.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.129-137
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• 2013

From the cooked-rice as a raw material, activated carbons throughout a hydrothermal synthesis and vacuum soak of KOH for chemical activation were obtained. Activated carbon electrodes for electric double layer supercapacitors were prepared and electrochemical characteristics were examined. Including the specific surface area by BET method and pore size distribution by NLDFT method, physical properties of activated carbons were investigated by means of SEM, EDS, XRD, and TG analyses. Cycle voltammetry and AC-impedance measurements were conducted to confirm the electrochemical characteristics for the electrodes. From hydrothermal synthesis, $5{\sim}7{\mu}m$ diameters of spherical carbons were obtained. After the activation at $800^{\circ}C$, it was notable for the activated carbon to be the specific surface $1631.8cm^2/g$, pore size distribution in 0.9~2.1 nm, and micro-pore volume $0.6154cm^3/g$. As electrochemical characteristics of the activated carbon electrode in 6M KOH electrolyte, it was confirmed that the specific capacitances of 236, 194, and 137 F/g at the scan rate of 5, 100, and 500 mV/s respectively were exhibited and 91.2% of initial capacitance after 100,000 cycles at 200 mV/s was maintained.