• Korean Journal of Materials Research
• /
• v.31 no.5
• /
• pp.264-271
• /
• 2021

Porous carbons have been widely used as electrode material for supercapacitors. However, commercial porous carbons, such as activated carbons, have low electrochemical performance. Nitrogen-doping is one of the most promising strategies to improve electrochemical performance of porous carbons. In this study, nitrogen self-doped porous carbon (NPC) is prepared from melamine foam by carbonization to improve the supercapacitive performance. The prepared NPC is characterized in terms of the chemical structures and elements, morphology, pore structures, and electrochemical performance. The results of the N₂ physisorption measurement, X-ray diffraction, and Raman analyses reveal that the prepared NPC has bimodal pore structures and pseudo-graphite structures with nitrogen functionality. The NPC-based electrode exhibits a gravimetric capacitance of 153 F g^-1 at 1 A g^-1, a rate capability of 73.2 % at 10 A g^-1, and an outstanding cycling ability of 97.85 % after 10,000 cycles at 10 A g^-1. Thus, the NPC prepared in this study can be applied as electrode material for high-performance supercapacitors.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.2
• /
• pp.159-169
• /
• 2019

The activated carbon materials were prepared from waste biomass by ultrasonic assisted chemical activation method (UCA), ultrasonic assisted physical activation method (UPA) and Manganese nitrogen doped carbon (Mn/N-C). The XRD result shows the turbostatic (fully disordered) structure. The cyclic voltammetry test was done at 50 mV/s using 1M sodium sulfate and the values of specific capacitance were found to be 93, 100 and 115 F/g for UCA, UPA and Mn/N-C respectively. The power density values for the samples UCA, UPA and Mn/N-C were found to be 46.04, 87.97 and 131.42 W/kg respectively. The electrochemical impedance spectroscopy was done at low frequency between 1 to 10 kHz. The Nyquist plot gives the resistant characteristics of the materials due to diffusional resistance at the electrode-electrolyte interface. The Energy Dispersive X-Ray Spectroscopyanalysis (EDAX) analysis showed that the percentage doping of nitrogen and manganese were 3.53 wt% and 9.44 wt% respectively. It is observed from the experiment Mn/N-C doped carbon show good physical and electrochemical properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.581-584
• /
• 2001

For the first time, a totally solid state electric double layer capacitor has been fabricated using an alkaline polymer electrolyte and an activated carbon powder as electrode material. The polymer electrolyte serves both as separator as well as electrode binder. The capacitor has a three-layer structure; electrode-electrolyte-electrode. A cyclic voltammetry and constant current discharge have been used for the determination of the electro chemical performance of capacitors.

• Journal of the Korean Electrochemical Society
• /
• v.17 no.4
• /
• pp.237-244
• /
• 2014

We report novel and simple structure of supercapacitors fabricated by using flexible glass fibre separators as templates. This method does not require separate electrodes, binders and high pressure/temperature to build the supercapacitor unit cells as required by the conventional technology. The supercapacitors were fabricated by drop-casting solution mixtures of carbonaceous active materials/gel electrolytes onto two sides of glass fibre separators. Two carbonaceous materials (nanoscaled activated carbons, multi-walled carbon nanotubes) were investigated as electrode materials. The electrochemical measurements reveal that the separatorbased supercapacitors using ACs successfully demonstrated significant mass specific capacitance ($22.3F\;g^{-1}$) and energy density ($9.7Wh\;kg^{-1}$), indicating this method can be useful in fabricating flexible, wearable and stretchable energy storage devices in more straightforward and cost-effective way than current technology.

• Clean Technology
• /
• v.19 no.4
• /
• pp.410-415
• /
• 2013

The supercapacitors were fabricated using silver (Ag) nano paste and activated carbon paste on the polyimide (PI) film and 5% potassium polyacrylate (PAAK) was used for gel electrolyte. In this paper, the current collector film and the electrode film were fabricated using screen printing. The thickness of printed silver paste was $7.3{\mu}m$ and the sheet resistance has the range of $5-7m{\Omega}/square$. An activated carbon with a surface area of $1,968m^2/g$, an electronic conducting agent (SUPER P, TIMCAL) and poly (4-vinylphenol) were mixed in 2-(2-buthoxyethoxy) ethyl acetate (BCA) with a ratio of 7:1:3 to fabricate the electrode paste. To analyze electrochemical characteristics, cyclic voltammetry was performed to evaluate the stability of the devices under the voltage range of -0.5-0.5 V. The calculated specific capacitances were 44.04 and 8.62 F/g for 10 and 500 mV/s scan rates, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.156.1-156.1
• /
• 2016

Nickel sulfide (NiS) is one of the most promising candidates as an electrode material for supercapacitors due to its good capacitive properties, high electrical conductivity and low cost. In addition to the development of the new electrode materials, nanostructuring the electrode surface is one of the main issues in enhancing the capacitive performance of the supercapacitors because the increased surface area can improve the charge transfer and energy storage processes occurring at the electrode surface. However, most nanofabrication techniques require complicated and delicate nanoprocesses, and hence are not suitable for practical use. In this work, we developed a simple method to fabricate nanostructured NiS electrodes by depositing NiS onto $TiO_2$ nanoparticles. First, $TiO_2$ nanoparticles were spin-coated on a fluorine-doped tin oxide (FTO) substrate, and then NiS layers were deposited onto the $TiO_2$ nanoparticles by consecutive dip-coatings in the solutions containing nickel and sulfur precursors. This nanostructured NiS electrode showed significantly improved capacitive properties compared to the electrode of NiS films deposited without $TiO_2$ nanoparticles. The asymmetric full-cell supercapacitor with this nanostructured NiS electrode and activated carbon electrode was also fabricated and investigated.

• Journal of Electrochemical Science and Technology
• /
• v.2 no.3
• /
• pp.152-156
• /
• 2011

A hybrid supercapacitor is fabricated using a composite material from $LiMn_2O_4$ (LMO) and activated carbon (AC) as the positive electrode and AC as the negative electrode to form the (LMO + AC)/AC system. Volume ratio (positive : negative) of electrodes is controlled to investigate of the power and energy balance. The (LMO + AC)/AC system shows better performances than the LMO/AC system. Especially, electrochemical impedance spectra, rate charge.discharge and cycle performance testing show that the (LMO + AC)/AC system have an outstanding electrochemical performance at volume ratios of (LMO + AC)/AC = 1 : 1.7 and 1 : 2. Electric double layer capacitor (EDLC) capacitance between AC of the positive electrode and AC of the negative electrode improves power density without loss of capacitance. Stable capacitance is achieved by lowering the positive electrode resistance and balancing the energy and power densities between the positive and negative electrodes by the addition of AC to the positive electrode at high current density.

• Applied Chemistry for Engineering
• /
• v.29 no.2
• /
• pp.191-195
• /
• 2018

In this study, the influence of microporous structures of activated carbon fibers (ACFs) on dimethyl methylphosphonate (DMMP) gas sensing properties as a nerve agent simulant was investigated. The pore structure was given to carbon fibers by chemical activation process, and an electrode was fabricated for gas sensors by using these fibers. The PAN based ACF electrode, which is an N-type semiconductor, received electrons from a reducing gas such as DMMP, and then electrical resistance of its electrode finally decreased because of the reduced density of electron holes. The sensitivity of the fabricated DMMP gas sensor increased from 1.7% to 5.1% as the micropore volume increased. It is attributed that as micropores were formed for adsorbing DMMP whose molecular size was 0.57 nm, electron transfer between DMMP and ACF was facilitated. In conclusion, it is considered that the appropriate pore structure control of ACFs plays an important role in fabricating the DMMP gas sensor with a high sensitivity.

• Korean Chemical Engineering Research
• /
• v.54 no.3
• /
• pp.293-298
• /
• 2016

A hydrogel electrolyte consisting of 6 M KOH aqueous solution, potassium polyacrylate (PAAK, 3 wt.%), and a hydrophilic silica OX50 (1 wt.%) was prepared to use as an electrolyte medium coated on a Scimat separator of activated carbon supercapacitor. The silica particle distributed homogeneously on surface pores of the separator to increase ionic conductivity and electrochemical stability of the hydrogel electrolyte. The silica addition also involved superior specific capacitance even at higher scan rates due to decrease in interfacial resistance between hydrogel electrolyte and activated carbon electrode.

• Applied Chemistry for Engineering
• /
• v.10 no.6
• /
• pp.814-821
• /
• 1999

The specific capacitance characteristics of the electric double layer capacitors(ELDC) which were made of phenol based activated carbon fiber(ACF) electrodes. Also the effect of aqueous electrolytes on the cell performance has been investigated with respect to different specific surface areas of electrodes and different kinds of aqueous electrolytes. It has been shown that larger surface area and pore size, higher conductivity of electrodes, and higher ion mobility of electrolytes have better specific capacitances. It has been found that heat treatment at $1200^{\circ}C$ and $CO_2$ post-activation at $900^{\circ}C$ of the electrode are effective to improve the specific capacitance over 145F/g and 165F/g, respectively. The EDLC showed high efficiency and long cycle life over 30000 cycles.