• Transactions of the Korean hydrogen and new energy society
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• v.8 no.4
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• pp.161-171
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• 1997

$AB_2$ type Zr-based Laves phase alloys have been studied for potential application as negative electrode in Ni/MH batteries. However, They have a serious disadvantage of poor activation behavior in KOH solution. In this work, a new method of alloy design method was tried for improving Zr-based alloy activation. this method has focused on phase controlling to make multi-phase microstructure. In the case of multi-phase Zr-V-Mn-Ni shows good performance in activation, but activation mechanism has not been known. So, we were in search of elucidating this mechanism, Using morphological and electrochemical analysis, we could find that surface morphology and electocatalytic activity of the alloy change during immersion in KOH solution. V-rich second phases are selectively corroded and dissolved and then become Ni-rich phases. Resulting from these surface reaction in KOH solution, self-hydrogen charging occurs through Ni-rich phase. However, the alloy has poor cyclic durability because of such a corrosion mechanism. Therefore, finally we developed durable alloys by substitution of other alloying element.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.273-279
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• 1998

In this paper, the proposed charging system consists of step charging mode and time-sharing equalization charging mode. As $\Delta$V=O point is detected, the proposed cut-off method will selectively cut off the only battery to reach the $\Delta$V=O point, preventing serial-connected batteries from undercharging. In the start of each step, the equalization charging mode is performed to reduce the capacity difference among the batteries. Though it is added to simple circuit for selective cut-off, comparing with recently used step-charging method, this system can improve the life cycle of battery and charging efficiency, and be also very effective for preventing the batteries from overcharging and undercharging.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.294-299
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• 2001

Effects of the surface fluorination on the electrochemical charge-discharge properties of $Mg_2$Ni electrode in Ni-MH batteries fabricated by mechanical alloying were investigated. After 20h ball milling, Mg and Ni powder formed nanocrystalline $Mg_2$Ni. Discharge capacity of this alloy increased greatly at first one cycle, but due to the formation of Mg(OH)$_2$ passive layer, it showed a rapid degradation in alkaline solution within 10cyc1es. In case of 6N KOH +xN KF electrolyte (x = 0.5, 1, 2), a continuous and stable fluorinated layer formed by adding excess F$^{[-10]}$ ion, increased durability of $Mg_2$Ni electrode greatly and high rate discharge capability(90-100mAh/g). 2N KF addition led to the highest durability of all tested here. The reason of the improvement is due to thin MgF$_2$, which can prevent the $Mg_2$Ni electrode from forming Mg(OH)$_2$layer that is the main cause of degradation.

• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.115-119
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• 2008

Single particle of nickel hydroxide and the surface-treated one with cobalt element were performed to review the effect of LiOH additive in alkaline electrolyte for Ni-MH batteries using microelectrode test system. As a result of cyclic voltammetry, the electrochemical behaviors such as the oxidation/reduction and oxygen evolution reaction are clearly observed for a single particle of nickel hydroxide, respectively. Furthermore, the reduction current peak of nickel hydroxide added with LiOH in electrolyte was very low and broad compared with the normal nickel hydroxide without an additive LiOH, which had a bad effect to the crystallization structure of nickel hydroxide. However, it was found that capacity and cycle properties of the nickel hydroxide treated with cobalt greatly increased by the addition of LiOH.

• Resources Recycling
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• v.27 no.1
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• pp.22-30
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• 2018

In order to industrially recycle nickel, cobalt and rare earth elements included in waste NiMH batteries, electrode powder scraps were recovered by dismantle, crushing and classification from automobile waste battery module. As a result of leaching recovered electrode powder scrap with sulfuric acid solution, 99% of nickel, cobalt and rare earth elements were leached under reaction conditions of 1.0 M sulfuric acid solution, pulp density 25 g/L and reaction temperature $90^{\circ}C$ for 4 hours. In addition, the rare earth elements were able to separate from nickel / cobalt solution as cerium, lanthanum and neodymium precipitated under pH 2.0 using 10 M NaOH.

• Resources Recycling
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• v.26 no.2
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• pp.3-10
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• 2017

Rare earth elements with high purity are demanded for the manufacture of advanced materials. Light rare earth elements are contained in domestic monazite and Ni-MH batteries. In this paper, solvent extraction to separate the light rare earth elements from hydrochloric acid leaching solutions of these resources was discussed. A mixture of cationic and tertiary amine shows synergistic effect on the extraction of LREEs and the extent of pH decrease during extraction is reduced. The effect of solution pH on the extraction and synergism was reviewed. Acquisition of the operation data with mixer-settler on the separation of LREEs by this mixture is necessary to develop a process.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.53-57
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• 2001

When an EV is parked for a long period time, the battery capacity naturally decreases due to selfdischarge. Therefore, this effect must be considered for the accurate measurement of the state of charge of EV battery. Battery selfdischarge simulations using the design of experiments among computer simulation methods are compared with experimental data for Ni/MH batteries for electric vehicles. The motivation is to predict the selfdischarge rate of the battery for electric vehicle at all temperature conditions and standing time when electric vehicle could be operated. We developed a general equation representing the seudischarge rate of the electric vehicle battery using design of experiments, and the equation is determined by temperature and standing time of the battery. We selected Ni/MH battery, 12 V-95 Ah, for pure electric vehicle for this study. ID develop the equation using design of experiments we selected temperature range of $-20^{\circ}~30^{\circ}C$ and standing time of 1 day$\~15$ days. We conducted several selfdischarge tests of Ni/MH battery to verify the integrity of the equation. The results showed that the computation values were in good agreement with experimental data.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.200-206
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• 2014

This paper describes magnetically levitated vehicle with hybrid magnets, which have been studied by the authors in place of streetcars or conveyance system. An experimental vehicle of 20kg was magnetically levitated by using a small number of dry-cell batteries, which consisted of 10 Ni-MH cells of 1900mAh in series. The magnets were activated sequentially, because the internal resistance of the batteries suppressed the maximum current. The vehicle was kept levitating for about 2 hours and was stable against disturbance due to instantaneous external force. In this paper, dynamic characteristics of the magnetically levitated vehicle using a small number of dry cell batteries are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.45-49
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• 2006

Electrochemical hydrogenation/dehydrogenation properties were studied for a single particle of a Mm-based(Mm : minh metal) hydrogen storage alloy($MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3}$) for fuel cell and Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and the potential-step experiment was carried out to determine the apparent chemical diffusion coefficient of hydrogen atom($D_{app}$) in the alloy. Since the alloy particle we used here was a dense, conductive sphere, the spherical diffusion model was employed for data analysis. $D_{app}$ was found to vary the order between $10^{-9}\;and\;10^{-10}[cm^2/s]$ over the course of hydrogenation and dehydrogenation process. Compared with the conventional composite film electrodes, the single particle measurements using the microelectrode gave more detailed, true information about the hydrogen storage alloy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.2
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• pp.85-90
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• 2018

For the recovering rare earths in the spent nickel-metal hydride batteries, 10 M NaOH is added to the solution leached with sulfuric acid. The rare earth powders were precipitated at rate of 98 % at the condition of pH 2.0 or less. The recovered rare earth complex precipitate increased the leaching rate to nitric acid by heat treatment at $800^{\circ}C$ for 4 hours. Subsequently secondary precipitation was performed by adding oxalic acid to the solution in which the rare earth complex precipitate was dissolved. The re-precipitated rare earth powders were converted into oxide form through heat treatment at $800^{\circ}C$ for 4 hours with purity of 99.5 %.