• Korean Journal of Materials Research
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• v.30 no.11
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• pp.636-640
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• 2020

Due to the serious air pollution problem, interest in eco-friendly vehicles is increasing. Solving the problem of pollution will necessitate the securing of high energy storage technology for batteries, the driving force of eco-friendly vehicles. The reason for the continuing interest in the transition metal oxide LiMO₂ as a cathode material with a layered structure is that lithium ions reveal high mobility in two-dimensional space. Therefore, it is important to investigate the effective intercalation and deintercalation pathways of Li⁺, which affect battery capacity, to understand the internal structure of the cathode particle and its effect on the electrochemical performance. In this study, for the cathode material, high nickel Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor is synthesized by controlling the ammonia concentration. Thereafter, the shape of the primary particles of the precursor is investigated through SEM analysis; X-ray diffraction analysis is also performed. The electrochemical properties of LiNi_0.8Co_0.1Mn_0.1O₂ are evaluated after heat treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.378-381
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• 1996

This study is to research Li$_{x}$Ni$_{2-x}$O$_2$ cathode for lithium chargeable battery. We investigated morphology and cell resistance, capacity and Ah efficiency of Li$_{x}$Ni$_{2-x}$O$_2$/Li cells using Li$_{x}$Ni$_{2-x}$O$_2$ prepared under air and $O_2$ flow. The (003)I/(104)I intensity ratio was 1.4. The cell resistance was increased with increasing Li in Li$_{x}$Ni$_{2-x}$O$_2$. The discharge capacity based on Li$_{x}$Ni$_{2-x}$O$_2$of 1st and 15th cycles was 135㎃h/g and 108㎃h/g, respectively. The Li$_{x}$Ni$_{2-x}$O$_2$ prepared with hexan under $O_2$ flow had a good properties. properties. properties.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.3
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• pp.179-184
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• 1999

In the past ten years, $LiMn_2O_4$-based spinels have been extensively studied as positive electrode materials for lithium-ion batteries. To improve the cycle performance of spinel $LiMn_2O_4$ as the cathode of 4V class lithium secondary batteries, spinel phases $LiMn_2O_4$ were prepared at various temperatures ranging form 600-900$^{\cire}C$ in air. The results showed that charge.dischare capacity of $LiMn_2O_4$ varied at 1st temperature from $200^{\circ}C to 600^{\circ}C$ increase with increasing temperature. $LiMn_2O_4$ synthesized at 2nd temperature $750^{\circ}C$excellent charge.discharge capacity, efficiency and cyclability compared to the samplesynthesized different temperatures. The value of lst charge.discharge capacity was 121mAh/g, 118mAh/g, Also, the efficiency value was about 97%.

• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.39-44
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• 1998

$LiCoO_2$ powder was synthesized in an aqueous solution by a sol-gel method and used as a cathode active material for a lithium ion rechargeable battery. The layered $LiCoO_2$ powders were prepared by igniting in air for 12 hrs at 600 ℃ $(600-LiCoO_2)$ and 850 ℃ $(850-LiCoO_2)$. The structure of the $LiCoO_2$ powder was assigned to the space group R bar 3 m (lattice parameters a=2.814 Å and c=14.04Å). The SEM pictures of $600-LiCoO_2$ revealed homogeneous and fine particles of about 1 μm in diameter. Cyclic voltammograms (CVs) of $600-LiCoO_2$ electrode displayed a set of redox peaks at 3.80/4.05 V due to the intercalation/deintercalation of the lithium ions into/out of the $LiCoO_2$ structure. CVs for the $850-LiCoO_2$ electrode had a major set of redox peaks at 3.88/4.13 V, and two small set of redox peaks at 4.18/4.42 V and 4.05/4.25 V due to phase transitions. The initial charge-discharge capacity was 156-132 mAh/g for the $600-LiCoO_2$ electrode and 158-131 mAh/g for the $850-LiCoO_2$ electrode at the current density of 0.2 mA/cm2. The cycleability of the cell consisting of the $600-LiCoO_2$ electrode was better than that of the $850-LiCoO_2$. The diffusion coefficient of the $Li^+$ ion in the $600-LiCoO_2$ electrode was calculated as $4.6{\times}10^{-8}\; cm^2/sec$.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.503-508
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• 2005

A simple and effective method for the synthesis of LiMn$_{2}$O$_{4}$ powder as a cathode material for lithium secondary battery is reported. Micrometer size LiMn$_{2}$O$_{4}$ was prepared by combustion synthesis technique employing initial mixture of l.l LiNO$_{3}$ -1.3Mn-0.7MnO$_{2}$-1NaCl composition. Parametric study of the combustion process including molar ratio of Mn/MnO$_{2}$ and NaCl concentration were carried out under air atmosphere. The combustion products obtained were additionally heat treated at the temperature 900$^{\circ}C$ and the washed by distilled water. The results of charging-discharging characteristics revealed that LiMn$_{2}$O$_{4}$ cell synthesized in the presence of NaCl had a high capacity and much better reversibility than one formed without NaCl An approximate chemical mechanism for LiMn$_{2}$O$_{4}$ formation is proposed.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1125-1132
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• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.

• Journal of Powder Materials
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• v.23 no.4
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.16 no.2
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• pp.59-64
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• 2013

Using $Na_2CO_3$ and $MeSO_4$ (Me = Ni, Co and Mn) as starting materials, the precursor of $[Ni_{0.6}Co_{0.2}Mn_{0.2}]CO_3$ has been synthesized by carbonate co-precipitation. The precursor was mixed with $Li_2CO_3$, and calcined at 750, 850, and$950^{\circ}C$ in air. Effect of calcinations temperature on characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ cathode materials was investigated. The structure and characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ were determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrochemical measurements. The X-ray diffraction (XRD) results show that the intensity ratio of $I_{(003)}/I_{(104)}$ increased and the R-factor ratio decreased with the increase of calcinations temperature. And Scanning electron microscopy (SEM) result show that the primary particle size increased. Especially, the $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ calcined at $950^{\circ}C$ for 24 H shows excellent electrochemical performances with reversible specific capacity of $165.3mAhg^{-1}$ [cut-off voltage 2.5~4.3 V, 0.1 C($17mAhg^{-1}$)] and good capacity retention of 95.4% after 50th charge/discharge cycles[cut-off voltage 2.5~4.3 V, 1 C($170mAhg^{-1}$)].