• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.861-864
• /
• 2002

Deformation of the specimen was investigated on hydrogen absorption-desorption cycling. In order to study this problem, the cold rolled palladium thin plate as the specimen had been used. By using the electrochemical method, the palladium plate specimen was cyclically hydrogenated in the 0.1 mol $H_2SO_4$ electrolyte. As results, it is noted that the thickness of the plate specimen gradually increased in increasing hydrogenation cycles whereas the width and the length decreased. Also, grains in the plate specimen were greatly deformed after hydrogenation cycling. But hydrogen absorption rate scarcely changed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.829-832
• /
• 2002

Deformation of the specimens was investigated on hydrogen absorption-desorption cycling. In order to study this problem, the cold rolled and the annealed palladium thin plate as specimens had been used. By using the electrochemical method, the palladium plate specimens were cyclically hydrogenated in the 0.1mol $H_2SO_4$ electrolyte. As results, it is noted that the thickness of the plate specimens gradually increased in increasing hydrogenation cycles whereas the width and the length decreased. Also, Deformation of the cold rolled palladium specimen was lager than the annealed palladium specimen. And grains in the plate specimen were greatly deformed after hydrogenation cycling. But hydrogen absorption rate scarcely changed.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.2
• /
• pp.284-291
• /
• 1997

The electrode characteristics of two kinds of metal hydride electrodes using V-Ti (V-rich) based alloy were studied, in which one electrode was prepared by sintering the mixture of V-Ti alloy and Ni powders by a rapid thermal annealing technique and the other one was prepared using V-Ti-Ni ternary alloy, The discharge capacities of all electrodes during the charge-discharge cycling were completely deteriorated within 10 cycles. It appeared that the deterioration of the electrodes was caused by the dissolution of V in the near-surface region into the electrolyte and the formation of $TiO_2$ layer on the alloy particle surface. This degradation mechanism was supported by the facts that V is main hydride forming element and $TiO_2$ has very low electrical conductivity and hydrogen diffusivity.

• Journal of the Korean Electrochemical Society
• /
• v.5 no.1
• /
• pp.30-38
• /
• 2002

Disordered carbon and boron-substituted disordered carbons $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ were synthesized by Pyrolysis of LPG(liquid Propane gas)and $BCl_3$. Their electrochemical properties as anode materials for Li-ion secondary batteries were then investigated. When PVDF is added to the sample in a weight ratio 5 : 95, the disordered carbon with x=0.00 had the first discharge capacity 374 mAh/g. Its cycling performance was relatively good from the second cycle and it had the discharge capacity 258 mAh/g at the 10th cycle. When PVDF is added to the sample in a weight ratio 5 : 95, the sample with x=0.05 among the samples $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ exhibited the largest first discharge capacity 860 mAh/g and discharge capacity 181 mAh/g at the 10th cycle. All the samples had similar cycling performances from the second cycle. The sample $C_{0.90}B_{0.10}$ showed the best electrochemical properties as a anode materials fur Li-ion secondary battery from the view points of the first discharge capacity(853 mAh/g when $10w1.\%$ PVDF is used), cycling performance, discharge capacity(400mAh/g at the 10th cycle when $10wt.\%$ PVDF is used). All the samples showed generally larger charge and discharge capacities when $10wt.\%$ PVDF ratter than $5wt.\%$ PVDF is used. The plateau region in the range of voltage lower than 1.25V becomes larger probably since the structure becomes less disordered by the addition of boron. When boron is added, the charge and discharge capacities decreased suddenly at the second cycle. This may be become only a part of Li are reversibly deintercalated and intercalated and a part of Li which are strongly combined with B are not deintercalated. The increases in charge and discharge capacities are considered to be resulted from the increase in the potential of Li in the boron-added carbons, caused by the strengthening of the chemical bond between the intercalated Li and the boron-carbon host since the boron acts as electron acceptor.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1382-1385
• /
• 2003

Deformation on shapes of the hydrogen absorption metal in this paper was investigated on hydrogen absorption-desorption cycling. In order to study this problem, the cold rolled palladium plate and the cold extrusion palladium bar as specimens had been used. By using the electrochemical method, the palladium specimens were cyclically hydrogenated in the 0.1 mol H$_2$SO$_4$ electrolyte. As results, it is noted that the thickness of the plate specimen gradually increased in increasing hydrogenation cycles whereas the width and the length decreased. But both the diameter and the length of the bar specimen increased with increasing hydrogenation cycles. Also, grains in the plate specimen were greatly deformed after hydrogenation cycling whereas internal grains in the bar specimen were pulverized. And deterioration of the hydrogen absorption rate of the bar specimen was lager than the plate specimen.

• Journal of the Korean Electrochemical Society
• /
• v.12 no.2
• /
• pp.162-166
• /
• 2009

The carbon-coated Si/Cu powders were synthesized by mechanical ball-milling and hydrocarbon gas decomposition methods at high temperature. The carbon-coated Si/Cu powder was used as anode for lithium secondary battery and its electrochemical behavior was investigated. In addition, the carbon-coated Si/Cu/graphite composite anode material was prepared using natural graphite powder and their electrochemical characteristics were compared with natural graphite anode. The specific capacity of carbon-coated Si/Cu anode increased to the initial 10 cycles. The carbon-coated Si/Cu/graphite composite anode exhibited the reversible specific capacity of 450mAh/g and the first cycle efficiency of 81.3% at $0.25mA/cm^2$. The cycling performance of the composite anode was similar to that of pure graphite anode except the reversible specific capacity value.

• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.6
• /
• pp.592-611
• /
• 2021

In this study a rarely available high-throughput cycling data set of 124 commercial lithium iron phosphate/graphite cells cycled under fast-charging conditions, with widely varying cycle lives ranging from 150 to 2,300 cycles including in-cycle temperature and per-cycle IR measurements. We worked out own Python codes which reproduced the various data plots and machine learning approaches for cycle life prediction using early cycles and more details not presented in the article and the supplementary information. Particularly, we applied regularized ridge, lasso and elastic net linear regression models using features extracted from capacity fade curves, discharge voltage curves, and other data such as internal resistance and cell can temperature. We found that due to the limitation in the quantity and quality of the data from costly and lengthy battery testing a careful hyperparameter tuning may be required and that model features need to be extracted based on the domain knowledge.

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

• Journal of the Korean Electrochemical Society
• /
• v.1 no.1
• /
• pp.45-51
• /
• 1998

[ $AB_2-type$ ] alloy, one kind of hydrogen storage alloys used as an anode of Ni-MH batteries, has large discharge capacity but has remaining problems regarding initial activation, cycle life and self-discharge. This study investigates the effects of Cr-addition and fluorination after La-addition on $Zr_{0.7}Ti_{0.3}V_{0.4}Mn_{0.4}Ni_{1.2}$, composition $AB_2-type$ alloy. EPMA and SEM surface analysis techniques were used and the crystal structure was characterized by XRD analysis. In addition, electrodes were fabricated out of the alloys and characterized by constant current cycling test, electrochemical impedance spectroscopy and potentiodynamic polarization. Cr-addition was found to be effective to cycle life and self-discharge but ineffective to initial activation due to formation of stable oxide film on surface. Fluorination after La-addition to the alloys improved initial activation remarkably due to formation of highly reactive particles on surface.

• Journal of the Korean Electrochemical Society
• /
• v.2 no.2
• /
• pp.106-111
• /
• 1999

The effect of the MG on the electrochemical charge-discharge properties of $CaNi_5$ hydrogen storage alloys was investigated under Ar and $H_2$ atmosphere. $CaNi_5$ alloy was partially decomposed to CaO and Ni phase during the MG process. The decomposition of $CaNi_5$ alloy was enhanced by the MG process which leads to crash and reformation of oxide layer on the alloy surface. As the MG process time increased, initial discharge capacity of the electrode was reduced, but the decay rate of the capacity compared to $CaNi_5$ alloys was slower. It may be described that the degradation of $MG-CaNi_5$ electrode was caused by the reduction of the reversible hydrogen reaction sites and increasing polarization resistance of hydrogen adsorption resulted from phase decomposition and disorder during the MG process, and/or by hydroxide formation during the electrochemical charge-discharge cycles.