• Korean Journal of Materials Research
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• v.29 no.12
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• pp.798-803
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• 2019

The self-discharge behavior of zinc-air batteries is a critical issue induced by corrosion and hydrogen evolution reaction (HER) of zinc anode. The corrosion reaction and HER can be controlled by a gelling agent and concentration of potassium hydroxide (KOH) solution. Various concentrations of KOH solution and polyacrylic acid have been used for gel electrolyte. The electrolyte solution is prepared with different concentrations of KOH (6 M, 7 M, 8 M, 9 M). Among studied materials, the cell assembled with 6 M KOH gel electrolyte exhibits the highest specific discharge capacity and poor capacity retention. Whereas, 9 M KOH gel electrolyte shows high capacity retention. However, a large amount of hydrogen gas is evolved with 9 M KOH solution. In general, the increase in concentration is related to ionic conductivity. At concentrations above 7 M, the viscosity increases and the conductivity decreases. As a result, compared to other studied materials, 7 M KOH gel electrolyte is suitable for Zn-air batteries because of its higher capacity retention (92.00 %) and specific discharge capacity (351.80 mAh/g) after 6 hr storage.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.4
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• pp.303-307
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• 2015

The effects of additive such as $H_2O_2$ in KOH electrolyte solution for the Aluminum/Air fuel cell were investigated with regard to electric power characteristics. The power generated by a Al/Air fuel cell was controlled by the KOH electrolyte solution and $H_2O_2$ depolarizer. Higher cell power was achieved when higher KOH electrolyte concentration and higher $H_2O_2$ depolarizer amount. The maximum power was increased by the increase amount $H_2O_2$ depolarizer, it was found that $H_2O_2$ depolarizer inhibits the generation of hydrogen and the polarization effect was reduced as a result. Internal resistance analysis was employed to elucidate the maximum power variation. Higher internal resistance created internal potential differences that drive current dissipating energy. In order to improve the output characteristics of the Al/Air fuel cell, it is thought to be desirable to increase the KOH electrolyte concentration and increase the $H_2O_2$ addition amounts.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.119-124
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• 2016

Plasma electrolytic oxidation (PEO) is a promising coating process to produce ceramic oxide on valve metals such as Al, Mg and Ti. The PEO coating is carried out with a dilute alkaline electrolyte solution using a similar technique to conventional anodizing. The coating process involves multiple process parameters which can influence the surface properties of the resultant coating, including power mode, electrolyte solution, substrate, and process time. In this study, ceramic oxide coatings were prepared on commercial Al alloy in electrolytes with different KOH concentrations (0.5 ~ 4 g/L) by plasma electrolytic oxidation. Microstructural and electrochemical characterization were conducted to investigate the effects of electrolyte concentration on the microstructure and electrochemical characteristics of PEO coating. It was revealed that KOH concentration exert a great influence not only on voltage-time responses during PEO process but also on surface morphology of the coating. In the voltage-time response, the dielectric breakdown voltage tended to decrease with increasing KOH concentration, possibly due to difference in solution conductivity. The surface morphology was pancake-like with lower KOH concentration, while a mixed form of reticulate and pancake structures was observed for higher KOH concentration. The KOH concentration was found to have little effect on the electrochemical characteristics of coating, although PEO treatment improved the corrosion resistance of the substrate material significantly.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.622-629
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• 1999

Effects of the fluorination in the $K_2$TiF\ulcorner solution and in-situ KF+ KOH electrolyte on the electrochemical charge-discharge properties of CaNi\ulcorner and the Mg-CaNi\ulcorner electrodes were investigated. In-situ fluorination in the KF+ KOH electrolyte compared with pre-fluorination in the$ K_2$TiF\ulcorner solution could improve the electrochemical cycling durability of CaNi\ulcorner and MG-CaN\ulcorner electrodes. The fluorinated layer on the alloy surface by pre-fluorination to improve the activity and anti-corrosion of the electrodes was dissolved in the pure KOH electrolyte during the cycling. The fluorinated layer was formed continuously on the surface of the electrode by thee2N KF addition in the 6N KOH electrolyte. The excess F\ulcorner ion addition in KOH electrolyte could improve the electrochemical cycling durability of CaNi\ulcorner and Mg-CaNi\ulcorner electrode. But, in case of MG-CaNi\ulcorner electrode, the discharge capacity of the electrode was reduced and the poor cycling property was shown with increasing of the MG process times.

• 한국전기화학회:학술대회논문집
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• 2001.10a
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• pp.46-46
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• 2001

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.115-120
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• 2015

The mechanical and electrochemical properties of poly(ethylene oxide) (PEO)-coated Rayon separator were characterized using potassium polyacrylate (PAAK)-KOH electrolyte. The supercapacitive properties of activated carbon supercapacitor adopting the Rayon/PEO separator and PAAK-KOH electrolyte was also tested. As the PEO content increased, the mechanical strength increased. Room-temperature ionic conductivity of over $10^{-2}S\;cm^{-1}$ was obtained at the PEO content lower than 5 wt.%, applicable to a supercapacitor. As a result, the specific capacitance at $1000mV\;s^{-1}$ of the activated carbon supercapacitor adopting the Rayon/PEO separator and PAAK-KOH electrolyte was highly stable after 1000th cycle. This was due to high rate-capability provided by the fact that PEO coating could fix the entanglements among fiber filaments of Rayon.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.127-135
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• 1999

Nickel oxide films were prepard by using the electron beam evaporation technique. Coloring and bleaching experiments for cyclic durability were repeated in KOH electrolyte by cyclic voltammetry. Visible spectrophtometry was used to assess the stability of the transmittance in the degraded films. X-ray photoelectron spectroscopy results showed that the grain surface are oxygen-rich compared to the grain interiors in a NiO film. Open circuit memory of colored films is about 400hours in lN KOH. The rate of self discharge was evaluated by measuring the transmittance at 550nm of a fully oxidized NiO film. The rate of self discharge was increased polynomially with time and the film is nearly bleached after about 400hours. It was also found that the degraded film by repeated cycles in the KOH solution changed the grain shape of film surface The film prepared under a vacuum pressure of $3\times10^{-4}$ mbar was found to be rather stable when subjected to the repeated coloring and bleaching cycles in KOH electrolyte. Band theory applied to explain the electrochromic mechanism was discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.540-540
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• 2008

본 논문에서는 KOH 전해액을 이용하여 Cu 막의 부동태층의 형성을 I-V를 통해 평가하였으며, 이를 토대로 최적화된 전압과 시간을 알 수 있었다. 또한, SEM, EDS, XRD를 통해 표면 품질 및 성분 분석을 비교 분석하였다.

• Corrosion Science and Technology
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• v.10 no.2
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• pp.71-75
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• 2011

Corrosion properties of Al-0.3Ga-0.3Sn, Al-0.3Mn-0.3Ga, and Al-0.3Mn-0.3Sn alloys were examined to develop an anode material for Al-air battery with alkaline aqueous or ethanol electrolyte. The results of potentiodynamic polarization tests showed that the electrode potential of the Al alloys were lower than the pure Al, implying the cell voltage can be increased by using one of these alloys for an anode in 4 M KOH aqueous solution. The corrosion rate appeared to be increased by alloying Ga but to be reduced by Sn and Mn in the aqueous solution. The ethanol solution is expected to improve the cell performance in that the electrode potential and the corrosion rate of Al were lower in ethanol solution than in aqueous solution. However the Al-(Ga, Sn, Mn) alloys are not favorable in ethanol solution because of the high potential and corrosion rate.

• 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.