• Title/Summary/Keyword: Capacitance in KOH

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MnCo2S4/CoS2 Electrode for Ultrahigh Areal Capacitance

  • Pujari, Rahul B.;Lokhande, C.D.;Lee, Dong-Weon
    • Journal of Sensor Science and Technology
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    • v.29 no.4
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    • pp.215-219
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    • 2020
  • MnCo2S4/CoS2 electrode with highly accessible electroactive sites is prepared using the hydrothermal method. The electrode exhibits an areal capacitance of 0.75 Fcm-2 at 6 mAcm-2 in 1 M KOH. The capacitance is further increased to 2.06 Fcm-2 by adding K3Fe(CN)6 and K4Fe(CN)6 (a redox couple) to KOH. This increment is associated with the redox-active properties of cobalt and manganese transition metals, as well as the ion pair of [Fe(CN)6]-3/[Fe(CN)6]-4. The capacitance retention of the MnCo2S4/CoS2 electrode is 87.5% for successive 4000 charge-discharge cycles at 10 mAcm-2 in a composite electrolyte system of KOH and ferri/ferrocyanide. The capacitance enhancement is supported by the lowest equivalent series resistance (0.62 Ωcm-2) of MnCo2S4/CoS2 in the presence of redox additive couple compared with the bare KOH electrolyte.

Electrochemical Properties of Activated Carbon Supecapacitor Adopting Poly(acrylonitrile) Separator Coated by Polymer-Alkaline Electrolytes (고분자-알칼리 전해질이 코팅된 Poly(acrylonitrile) 분리막을 적용한 활성탄 수퍼커패시터 특성)

  • Kim, Kwang Man;Lee, Young-Gi;Ko, Jang Myoun
    • Korean Chemical Engineering Research
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    • v.55 no.4
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    • pp.467-472
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    • 2017
  • Alkaline electrolytes consisting of 6 M KOH and polymer (PEO, PVA, and PAAK) are coated on PAN nonwoven fabrics as a separator, and the electrochemical properties of the activated carbon supercapacitor adopting them are investigated in terms of redox behavior, specific capacitance, and interfacial impedance. Although the interaction between polymer and KOH are comparatively inactive in PEO and PVA, PAAK (3 wt.%)-KOH forms a hydrogel phase by active interactions between $COO^-K^+$ in side-chain of PAAK and $K^+OH^-$ from alkaline electrolyte solution, improving ionic conduction of electrolytes and the electrochemical properties of the supercapacitor. As a result, the activated supercapacitor adopting the PAAK-KOH shows the superior specific capacitance of $46.8Fg^{-1}$ at $100mVs^{-1}$.

High-energy-density activated carbon electrode for organic electric-double-layer-capacitor using carbonized petroleum pitch

  • Choi, Poo Reum;Kim, Sang-Gil;Jung, Ji Chul;Kim, Myung-Soo
    • Carbon letters
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    • v.22
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    • pp.70-80
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    • 2017
  • Activated carbons (ACs) have been used as electrode materials of electric double-layer capacitors (EDLC) due to their high specific surface areas (SSA), stability, and ecological advantages. In order to make high-energy-density ACs for EDLC, petroleum pitch (PP) pre-carbonized at $500-1000^{\circ}C$ in $N_2$ gas for 1 h was used as the electrode material of the EDLC after KOH activation. As the pre-carbonization temperature increased, the SSA, pore volume and gravimetric capacitance tended to decrease, but the crystallinity and electrode density tended to increase, showing a maximum volumetric capacitance at a medium carbonization temperature. Therefore, it was possible to control the crystalline structure, SSA, and pore structure of AC by changing the pre-carbonization temperature. Because the electrode density increased with increasing of the pre-carbonization temperature, the highest volumetric capacitance of 28.4 F/cc was obtained from the PP pre-carbonized at $700^{\circ}C$, exhibiting a value over 150% of that of a commercial AC (MSP-20) for EDLC. Electrochemical activation was observed from the electrodes of PP as they were pre-carbonized at high temperatures above $700^{\circ}C$ and then activated by KOH. This process was found to have a significant effect on the specific capacitance and it was demonstrated that the higher charging voltage of EDLC was, the greater the electrochemical activation effect was.

Performance of Electric Double Layers Capacitor Using Activated Carbon Materials from Rice Husk as Electrodes

  • Nguyen, Tuan Dung;Ryu, Jae Kyung;Bramhe, Sachin N.;Kim, Taik-Nam
    • Korean Journal of Materials Research
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    • v.23 no.11
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    • pp.643-648
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    • 2013
  • Activated carbon (AC) was synthesized from rice husks using the chemical activation method with KOH, NaOH, a combination of (NaOH + $Na_2CO_3$), and a combination of (KOH + $K_2CO_3$) as the chemical activating reagents. The activated carbon with the highest surface area (around $2000m^2/g$) and high porosity, which allows the absorption of a large number of ions, was applied as electrode material in electric double layer capacitors (EDLCs). The AC for EDLC electrodes is required to have a high surface area and an optimal pore size distribution; these are important to attain high specific capacitance of the EDLC electrodes. The electrodes were fabricated by compounding the rice husk activated carbons with super-P and mixed with polyvinylidene difluoride (PVDF) at a weight ratio of 83:10:7. AC electrodes and nickel foams were assembled with potassium hydroxide (KOH) solution as the electrolyte. Electrochemical measurements were carried out with a three electrode cell using 6 M KOH as electrolyte and Hg/HgO as the reference electrode. The specific capacitance strongly depends on the pore structure; the highest specific capacitance was 179 F/g, obtained for the AC with the highest specific surface area. Additionally, different activation times, levels of heating, and chemical reagents were used to compare and determine the optimal parameters for obtaining high surface area of the activated carbon.

Comparative electrochemical study of sulphonated polysulphone binded graphene oxide supercapacitor in two electrolytes

  • Mudila, Harish;Zaidi, M.G.H.;Rana, Sweta;Alam, S.
    • Carbon letters
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    • v.18
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    • pp.43-48
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    • 2016
  • Sulphonated polysulphone (SPS) has been synthesized and subsequently applied as binder for graphene oxide (GO)-based electrodes for development of electrochemical supercapacitors. Electrochemical performance of the electrode was investigated using cyclic voltammetry in 1M Na2SO4 and 1M KOH solution. The fabricated supercapacitors gave a specific capacitance of 161.6 and 216.8 F/g with 215.4 W/kg and 450 W/kg of power density, in 1M Na2SO4 and 1M KOH solutions, respectively. This suggests that KOH is a better electrolyte than Na2SO4 for studying the electrochemical behavior of electroactive material, and also suggests SPS is a good binder for fabrication of a GO based electrode.

Electrochemical Characteristics of Pseudocapacitor Using Aqueous Polymeric Gel Electrolyte (수용성 폴리머 겔 전헤액을 사용한 Pseudocapacitor의 전기화학적 특성)

  • Park, Soo-Gil
    • Journal of the Korean Electrochemical Society
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    • v.6 no.2
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    • pp.158-160
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    • 2003
  • We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400 F/g (specific capacitance) and good cycleability. But, it had serious demerits of low voltage range under 0.5 V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. We report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over 250 F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around 100 F/g capacitance. This capacitance was only electric double layer capacitance of active surface area. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Itis very hard to reach resistive layer. So, we have studied on pretreatment of electrode to contain working ions easily. We'll report more details.

Activated carbons prepared from mixtures of coal tar pitch and petroleum pitch and their electrochemical performance as electrode materials for electric double-layer capacitor

  • Lee, Eunji;Kwon, Soon Hyung;Choi, Poo Reum;Jung, Ji Chul;Kim, Myung-Soo
    • Carbon letters
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    • v.16 no.2
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    • pp.78-85
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    • 2015
  • Activated carbons (ACs) were prepared by activation of coal tar pitch (CTP) in the range of $700^{\circ}C-1000^{\circ}C$ for 1-4 h using potassium hydroxide (KOH) powder as the activation agent. The optimal activation conditions were determined to be a CTP/KOH ratio of 1:4, activation temperature of $900^{\circ}C$, and activation time of 3 h. The obtained ACs showed increased pore size distribution in the range of 1 to 2 nm and the highest specific capacitance of 122 F/g in a two-electrode system with an organic electrolyte, as measured by a charge-discharge method in the voltage range of 0-2.7 V. In order to improve the performance of the electric double-layer capacitor electrode, various mixtures of CTP and petroleum pitch (PP) were activated at the optimal activation conditions previously determined for CTP. Although the specific capacitance of AC electrodes prepared from CTP only and the mixtures of CTP and PP was not significantly different at a current density of 1 A/g, the AC electrodes from CTP and PP mixtures showed outstanding specific capacitance at higher current rates. In particular, CTP-PP61 (6:1 mixture) had the highest specific capacitance of 132 F/g, and the specific capacitance remained above 90% at a high current density of 3 A/g. It was found that the high specific capacitance could be attributed to the increased micro-pore volume of ACs with pore sizes from 1 to 2 nm, and the high power density could be attributed to the increased meso-pore volume.

Study on High Density Activated Carbons for Electrode Materials of Supercapacitor (초고용량 커패시터 전극활성물질용 고밀도 활성탄 제조 및 특성 연구)

  • Roh, Kwang Chul;Park, Jin Bae;Lee, Chul-Tae;Park, Chul Wan
    • Applied Chemistry for Engineering
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    • v.18 no.4
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    • pp.381-385
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    • 2007
  • High density activated carbons electrode materials, for supercapacitor were prepared by chemical KOH activation of cokes as the starting material under Ar atmosphere. By controlling the synthesis conditions and reducing KOH quantity in the activation step, the specific surface area of the product was decreased. BET surface area was measured to be $500{\sim}1260m^2/g$, and the electrode density was in the range of $0.68{\sim}0.83g/cm^3$. Volumetric specific capacitance (unit cell test) was as high as 20 F/cc, which corresponds to gravimetric specific capacitance of about 95 F/cc on the basis of half cell test. It should be noted that the specific capacitance of the activated carbons prepared in this study is superior to that of commercial activated carbons.

Electrochemical Characteristics of Aqueous Polymeric Gel Electrolyte for Supercapaictor (수퍼커패시터용 수용성 고분자 젤 전해질의 전기화학적 특성)

  • Kim, Han-Joo;Ishikawa, Masashi;Morita, Masayuki;Park, Soo-Gil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.93-96
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    • 2001
  • We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400F/g (specific capacitance) and good cycleability. But, It had serious demerits of low voltage range under 0.5V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. we report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over than 250F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around l00F/g capacitance. This capacitance was only surface EDLC. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Its very hard to reach resistive layer. So, we have studied on pretreatment of electrode to contain working ions easily. We'll report more details.

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Electrochemical Characteristics of Aqueous Polymeric Gel Electrolyte for Supercapacitor (수퍼커패시터용 수용성 고분자 젤 전해질의 전기화학적 특성)

  • ;Masashi ISHIKAWA;Masayuki MORITA
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11a
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    • pp.93-96
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    • 2001
  • We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400F/g (specific capacitance) and good cycleability. But, It had serious demerits of low voltage range under 0.5V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. we report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over than 250F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around 100F/g capacitance. This capacitance was only surface EDLC. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Its very hard to reach resistive layer. So, e have studied on pretretmetn of electrode to contain working ions easily. We'll report more details.

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