• 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.

• Composites Research
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• v.35 no.6
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• pp.394-401
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• 2022

Two polymer precursors, polyvinylidene chloride-resin (PVDC-resin) and polyvinylidene fluoride (PVDF), are assembled into the microporous carbon by pyrolysis. Microporous carbon is advantageous as an electrode for supercapacitors that store electric charges through ion adsorption/desorption. The pyrolysis also turns the various heteroatoms of two precursors into functional groups, contributing to the additional charge storage. The analysis of the porous structure and function group during carbonization are important to develop the carbon for energy storage. Here, we analyzed the functional groups of two polymer-derived carbons through X-ray photoelectron spectroscopy. The electrochemical properties of the functional groups were explored in various pH electrolytes. The specific capacitance of two carbons in the acidic electrolyte (1 M H₂SO₄) was improved compared to that in the neutral electrolyte (0.5 M Na₂SO₄) due to the faradaic charge/discharge reaction of the quinone functional group. In particular, the carbon electrode derived from PVDC-resin exhibits a lower capacity than the carbon from PVDF due to the small micropores. In the alkaline electrolyte (6 M KOH), the highest specific capacitance and rate capability were obtained among the three electrolytes for both electrodes based on the facile adsorption of the constituent electrolyte ions (K⁺, OH^-).

• Clean Technology
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• v.27 no.1
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• pp.85-92
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• 2021

A solar water battery is a system that generates power using solar energy. It is a combination of photoelectrochemical cells and an energy storage system. It can simultaneously convert and store solar energy without additional external voltage. Solar water batteries consist of photoelectrodes, storage electrodes and counter electrodes, and their properties and combination are important for the performance and the efficiency of the system. In this study, we tried to find the effect that changing the components of solar water batteries has on its system. The effects of the counter electrode during discharge, the kinds of photoelectrode and storage electrode materials, and electrolytes on the solar energy conversion and storage capacitance were studied. The optimized composition (TiO2 : NaFe-PB : Pt foil) exhibited 72.393 mAh g-1 of discharge capacity after 15 h of photocharging. It indicates that the efficiency of solar energy conversion and storage is largely affected by the configuration of the system. Also, the addition of organic pollutants to the chamber of the photoelectrode improved the battery's photo-current and discharge capacity by efficient photoelectron-hole pair separation with simultaneous degradation of organic pollutants. Solar water batteries are a new eco-friendly solar energy conversion and storage system that does not require additional external voltages. It is also expected to be used for water treatment that utilizes solar energy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1128-1135
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• 2001

In this paper, a new HSG-Si formation technology, "seeding method', which employs Si$_2$H$_{6}$-molecule irradiation and annealing, was applied for realizing 64Mbit DRAMs. By using this technique, grain size controlled HSG-Si can be fabricated on in-situ phosphorous-doped amorphous-Si electrode. The new HSG-Si fabrication technology achieves twice the storage capacitance with high reliability for the stacked capacitors. In this technique, optimum process conditions of the phosphorous concentration, storage polysilicon deposition temperature and thickness of hemispherical grain silicon are in the range of 3.0-4.0E19atoms/㎤, 53$0^{\circ}C$ and 400$\AA$, respectively. In the 64M bit DRAM capacitor using optimum process conditions, limit thickness of dielectric nitride is about 65$\AA$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.617-621
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• 2016

In addition to the energy storage facilities based on high power technologies, Electric double layer capacitors(EDLC) are today's candidate for power quality stabilization. However, its low energy density is often inhibiting factor for application of electric power industry. Hybrid supercapacitor is an promising energy storage device that positioned between conventional EDLC and Li-ion battery. This paper describes the preparation and characteristics of a hybrid supercapacitor and module for power quality stabilization. A cylindrical 3200F hybrid supercapacitor ($60{\times}74.5mm$) was assembled by using the $Li_4Ti_5O_{12}$ electrode as an anode and activated carbon as a cathode. It shows 2.5 times higher energy density than conventional EDLC with the same volume. In order to determine the characteristics of the hybrid supercapacitor Module for uninterruptible power supply (UPS), hybrid supercapacitor cells were connected in series with active balancing circuit. At even the high current density of 14A(10C), Module prepared by 18 cells showed the capacitance of 170F at 30~50V, suggesting the applicability for UPS.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.781-792
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• 2016

This paper presents a new approach to enhance the data retention of logic-compatible embedded DRAMs. The memory bit-cell in this work consists of two logic transistors implemented in generic triple-well CMOS process. The key idea is to use the parasitic junction capacitance built between the common cell-body and the data storage node. For each write access, a voltage transition on the cell-body couples up the data storage levels. This technique enhances the data retention and the read performance without using additional cell devices. The technique also provides much strong immunity from the write disturbance in the nature. Measurement results from a 64-kbit eDRAM test chip implemented in a 130 nm logic CMOS technology demonstrate the effectiveness of the proposed circuit technique. The refresh period for 99.9% bit yield measures $600{\mu}s$ at 1.1 V and $85^{\circ}C$, enhancing by % over the conventional design approach.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.587-587
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• 2012

Supercapacitors, which can deliver significant energy with high power density, have attracted a lot of attention due to their potential application in energy storage. Among various oxide materials, sodium vanadate has been recognized as one of the most promising electrode materials because of high electrical conductivity. In addition, larger layer spacing of ${\beta}$-Na0.33V2O5 compared to V2O5 makes easier Li+ insertion. Moreover, ${\beta}$-Na0.33V2O5 has a tunnel like structure along b axis with 3 kinds of V site allowing it to enhance the ion intercalation by introducing three different intercalation sites along the tunnel. The tunnel can act as a fast diffusion path for ion diffusion, which can improve the overall charge storage kinetics. In this study, high quality single crystalline sodium vanadate (${\beta}$-Na0.33V2O5) nanowires were grown directly on Pt coated $SiO_2$ substrate by a facile chemical solution deposition method without employing catalyst, surfactant or carrier gas. The results show that great enhancement in capacitance was observed compared with previous reports.

• Journal of Electrochemical Science and Technology
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• v.6 no.1
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• pp.16-25
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• 2015

Transition metal oxide nanocrystalline materials are playing major role in energy storage application in this scenario. Nickel oxide is one of the best antiferromagnetic materials which is used as electrodes in energy storage devices such as, fuel cells, batteries, electrochemical capacitors, etc. In this research work, nickel oxide nanoparticles were synthesized by combustion route in presence of organic fuels such as, glycine, glucose and and urea. The prepared nickel oxide nanoparticles were calcined at 600℃ for 3 h to get phase pure materials. The calcined nanoparticles were preliminarily characterized by XRD, particle size analysis, SEM and EDAX. To prepare nickel oxide electrode materials for application in supercapacitors, the calcined NiO nanoparticles were mixed with di-methyl-acetamide and few drops of nafion solution for 12 to 16 h. The above slurry was coated in the graphite sheet and dried at 50℃ for 2 to 4 h in a hot air oven to remove organic solvent. The dried sample was subjected to electrochemical studies, such as cyclic voltammetry, AC impedance analysis and chrono-coulometry studies in KOH electrolyte medium. From the above studies, it was found that nickel oxide nanoparticles prepared by combustion synthesis using glucose as a fuel exhibited resulted in low particle diameter (42.23 nm). All the nickel oxide electrodes have shown better good capacitance values suitable for electrochemical capacitor applications.

• Journal of Electrochemical Science and Technology
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• v.9 no.1
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• pp.20-27
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• 2018

We describe a redox-enhanced electric double-layer capacitor (EDLC) that turns the electrolyte in a conventional EDLC into an integral, active component for charge storage-charge is stored both through faradaic reactions with soluble redox-active molecules in the electrolyte, and through the double-layer capacitance in a porous carbon electrode. The mixed-redox electrolyte, composed of vanadium and iodides, was employed to achieve high power density. The electrochemical reaction in a supercapacitor with vanadium and iodide was studied to estimate the charge capacity and energy density of the redox supercapacitor. A redox supercapacitor with a mixed electrolyte composed of 0.75 M NaI and 0.5 M $VOSO_4$ was fabricated and studied. When charged to a potential of 1 V, faradaic charging processes were observed, in addition to the capacitive processes that increased the energy storage capabilities of the supercapacitor. The redox supercapacitor achieved a specific capacity of 13.44 mAh/g and an energy density of 3.81 Wh/kg in a simple Swagelok cell. A control EDLC with 1 M $H_2SO_4$ yielded 7.43 mAh/g and 2.85 Wh/kg. However, the relatively fast self-discharge in the redox-EDLC may be due to the shuttling of the redox couple between the polarized carbon electrodes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.65-74
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• 2008

In Korea, air source heat pump system is less efficient than conventional heat source facilities, such as ground source, river water, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large resident building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing of sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller & heater.