• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.352-360
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• 2020

Lithium cobalt oxide (LiCoO₂, LCO) has been widely used as a cathode material for Li-ion batteries (LIBs) owing to its excellent electrochemical performance and highly reproducible synthesis even with mass production. To improve the energy density of the LIBs for their deployment in electro-mobility, the full capacity and voltage of the cathode materials need to exploited, especially by operating them at a higher voltage. Herein, we doped LCO with divalent calcium-ion (Ca²⁺) to stabilize its layered structure during the batteries' operation. The Ca-doped LCO was synthesized by two different routes, namely solid-state and co-precipitation methods, which led to different average particle sizes and levels of dopant's homogeneity. Of these two, the solid-state synthesis resulted in smaller particles with a better homogeneity of the dopant, which led to better electrochemical performance, specifically when operated at a high voltage of 4.5 V. Electrochemical simulations based on a single particle model provided theoretical corroboration for the positive effects of the reduced particle size on the higher rate capability.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.47-51
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• 2010

A powder, containing 80 percent of blue cobalt aluminate $(CoAl_2O_4)$ crystallites, was synthesized at $210 ^{\circ}C$ using a (metal nitrate-malonic acid-ammonium hydroxide-ammonium nitrate) system. The optimal amount of concentrated ammonia water and initial decomposition temperature were determined for the blue $CoAl_2O_4$ crystallites preparation. Three $CoAl_2O_4$ precursor pastes, corresponding to the various amounts of concentrated ammonia water, were prepared by evaporating the initial solutions in an electric furnace fixed at $80 ^{\circ}C$ under a vacuum of 25 torr. The initial solution was used to dissolve the starting materials. The powder with the maximum content (80%) of blue $CoAl_2O_4$ crystallites was prepared when the prepared precursor was decomposed at $210 ^{\circ}C$. The blue $CoAl_2O_4$ crystallite content in the prepared sample decreased with increasing initial decomposition temperature. For 0.2 mole of the $Al^{3+}$ ion, the chemical compositions of the precursor corresponded to molar ratios of 0.4, 1.40, 2.56 and 2.00 for the $Co^{2+}$ ion, malonic acid, ammonia and ammonium nitrate per mole of the $Al^{3+}$ ion, respectively. The blue $CoAl_2O_4$ crystallite content in the sample decreased with the amount of ammonia deviated from the optimal value. The characteristics of the powders were examined using X-ray diffraction, optical microscopy, Fourier transformation infrared spectroscopy and the Brunauer-Emmett-Teller technique.

• Resources Recycling
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• v.11 no.6
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• pp.12-17
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• 2002

Solvent extraction experiments have been performed to separate copper from $CuCl_2$-$NiCl_2$-$CoCl_2$$ solutions using Alamine336 and LIX84. The complex formation tendency between metal ions and chloride ion had a great effect on the distribution coefficients of Cu, Co and Ni ions and separation factor of Cu to Co and Ni. In the experimental ranges of chloride ion concentration from 0.5 to 4.0 M, LIX84 was superior to Alamine336 in separating copper from cobalt. When the volume percentage of LIX84 and Alamine336 was varied from 5 to 40%, LIX84 was more effective than Alamine336 in separating Cu from Co and Ni in solutions in which the chloride ion concentration was 1.0 M.

• Applied Biological Chemistry
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• v.42 no.4
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• pp.288-292
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• 1999

It was previously reported that cobalt(II) effectively suppresses the postharvest gravitropic response of snapdragon (Antirrhinum majus L.) (Kim et al. (1997) Agric. Chem. and Biotechnol. 40, 567-571). In this study, several factors affecting the suppression of the gravitropic response by cobalt ion were examined. When flower stalks of snapdragon were pretreated with several different cobalt salts, cobalt nitrate turned out to be the most effective not only in reducing the response but also in preserving the flower quality. We also tested the effects of various detergents which were added to cobalt(II) solution, finding that Tween-40 was the best among the tested with respect to the effectiveness as well as the flower quality. Based on these results, we optimized a protocol for the chemical treatment; that is, a suppressor solution containing 10 mM $CO(NO_3)_2$ and 0.05% Tween-40 was directly sprayed on the gravitropically sensitive region of cut flowers of snapdragon. The suppressor treatment gave rise to a significantly improved results when the flower stalks were stored at a lower temperature after the chemical treatment.

• Korean Journal of Microbiology
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• v.55 no.2
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• pp.123-130
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• 2019

Chelatase catalyzes the insertion of divalent metal into tetrapyrrole and plays a key role in the biosynthesis of metallated tetrapyrroles, such as cobalamin, siroheme, heme, and chlorophyll. SirB is a sirohydrochlorin (SHC) chelatase that generates cobalt-SHC or iron-SHC by inserting cobalt or iron into the center of sirohydrochlorin tetrapyrrole. To provide structural insights into the metal-binding and SHC-recognition mechanisms of SirB, we determined the crystal structure of SirB from Bacillus subtilis subsp. spizizenii (bssSirB) in complex with cobalt ions. bssSirB forms a monomeric ${\alpha}/{\beta}$ structure that consists of two domains, an N-terminal domain (NTD) and a C-terminal domain (CTD). The NTD and CTD of bssSirB adopt similar structures with a four-stranded ${\beta}-sheet$ that is decorated by ${\alpha}-helices$. bssSirB presents a highly conserved cavity that is generated between the NTD and CTD and interacts with a cobalt ion on top of the cavity using two histidine residues of the NTD. Moreover, our comparative structural analysis suggests that bssSirB would accommodate an SHC molecule into the interdomain cavity. Based on these structural findings, we propose that the cavity of bssSirB functions as the active site where cobalt insertion into SHC occurs.

• Journal of Life Science
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• v.19 no.8
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• pp.1139-1144
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• 2009

It has been known that brassiolide (BL) increased the positive gravitropic response and ethylene production in maize roots. This study examined the relationship between the BL-induced gravitropic response and ethylene Production. The ethylene production was inhibited to about 90% of the control by the treatment of $10^{-4}$ M aminoethoxyvinylglycine (AVG), the ethylene synthesis inhibitor. However, the gravitropic response did not show any significant changes compared to the control at $10^{-4}$ M AVG. In the case of treatment of AVG with BL, the ethylene production decreased to 60% of the control. However, the gravitropic response increased to the level which was induced by BL. Cobalt ions, another ethylene biosynthesis inhibitor, inhibited ethylene production, but not gravitropic response. When roots were treated with BL and cobalt ions, they showed the inhibition of ethylene production and promotion of gravitropic response. To elucidate the possibility that the effect of BL is related to auxin transport, roots were treated with TIBA (2,3,5-triiodobenzoic acid), an auxin transport inhibitor. Both treatment of TIBA alone and TIBA with BL stimulated ethylene production to about 96% and 132%, respectively. However, gravitropic response was completely inhibited in both treatments. Further, roots treated with BL in the presence of TIBA and IAA showed a negative gravitropic response, which means that IAA accumulates in the upper side of horizontal roots. Root elongation was also stimulated in this treatment. Taken together, these results suggest that BL might affect the differential distribution of internal IAA on roots, causing the regulation of positive gravitropic response.

• Resources Recycling
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• v.14 no.6 s.68
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• pp.28-36
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• 2005

A hydrometallurgical process to leach cobalt from the waste cathodic active material, $LiCoO_{2}$, and subsequently to separate it by solvent extraction was developed. The optimum leaching conditions for high recovery of colbalt and lithium were obtained: 2.0 M sulfuric acid, 5 $vol.\%$ hydrogen peroxide, $75^{\circ}C$ leaching temperature, 30 minutes leaching time and an initial pulp density of 100 g/L. The respective leaching efficiencies for Co and Li were $93\%$ and $94.5\%$. About $85\%$ Co was extracted from the sulfuric acid leach liquor containing 44.72 g/L Co and 5.43 g/L Li, using 1.5 M Cyanex272 as an extractant at the initial pH 5.0 and in organic to aqueous phase ratio of 1.6:1 under the single stage extraction conditions. The Co in the raraffinate was completely extracted by 0.5 M Na-Cyanex272 at the inital pH 5.0, and an organic to aqueous phase ratio of 1;1. The cobalt sulfate solution of higher than $99.99\%$ purity could be recovered from waste $LiCoO_{2}$, using a series of hydrometallurgical processes: sulfuric acid leaching of waste $LiCoO_{2}$- solvent extraction of Co by Na-Cyanex 271 - scrubbing of Li by sodium carbonate solution - stripping of Co by sulfuric acid solution.

• Nano
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• v.13 no.12
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• pp.1850139.1-1850139.10
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• 2018

$Co_3O_4$ nanocrystals have been synthesized via an ordinary one-step calcination of a cobalt-based 2D coordination polymer [Co(tfbdc)(4,4'-bpy)$(H_2O)_2$]. As an anode material for lithium-ion batteries, the obtained $Co_3O_4$ nanocrystals exhibit high reversible capacity, excellent cyclic stability and better rate capability. The reversible capacity of the $Co_3O_4$ nanocrystals maintains $713mA\;h\;g^{-1}$ after 50 cycles at a current density of $50mA\;g^{-1}$. Our results confirm that searching for metal oxides nanomaterials used as anode materials of lithium ion batteries via the calcinations of 2D coordination polymer is a new route.

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.398-406
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• 2022

To satisfy the growing demand for high-performance batteries, diverse novel anode materials with high specific capacities have been developed to replace commercial graphite. Among them, cobalt hydroxides have received considerable attention as promising anode materials for lithium-ion batteries as they exhibit a high reversible capacity owing to the additional reaction of LiOH, followed by conversion reaction. In this study, we introduced graphene in the fabrication of Co(OH)₂-based anode materials to further improve electrochemical performance. The resultant Co(OH)₂/graphene composite exhibited a larger reversible capacity of ~1090 mAh g^-1, compared with ~705 mAh g^-1 for bare Co(OH)₂. Synchrotron-based analyses were conducted to explore the beneficial effects of graphene on the composite material. The experimental results demonstrate that introducing graphene into Co(OH)₂ facilitates both the conversion and reaction of the LiOH phase and provides additional lithium storage sites. In addition to insights into how the electrochemical performance of composite materials can be improved, this study also provides an effective strategy for designing composite materials.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2006.05a
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• pp.95-99
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• 2006