• Journal of the Korean Electrochemical Society
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• v.17 no.4
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• pp.222-228
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• 2014

Ni-rich system $Li[Ni_{1-x-y}Co_xMn_y]O_2$ of lithium secondary battery cathode material keep a high discharge capacity. However, by the Ni content increases, there is a problem that the electrochemical properties and stability of the structure are reduced. In order to solve these problems, research for positive ion doping is performed. The one of the cathode material, barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01), was synthesized by the precursor, $Ni_{0.6}Co_{0.1}Mn_{0.3}(OH)_2$, from the co-precipitation method. The barium doped materials have studied the structural and electrochemical properties. The analysis of structural properties, results of X-ray diffraction analysis, and those results confirmed the change of the lattice from the binding energy in the structure by barium doping. Increased stability of the layered structure was observed by $I_{(006)}+I_{(102)}/I_{(101)}$(R-factor) ratio decrease. we expected that the electrochemical characteristics are improved. 23 mAh/g discharge capacity of barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01) electrode is higher than discharge capacity of $Li[Ni_{0.6}Co_{0.1}Mn_{0.3}]O_2$ due to decrease overvoltage. And, through the structural stability was confirmed that improved the cycle characteristics. We caused a reduction in charge transfer resistance between the electrolyte and the electrode was confirmed that the C-rate characteristics are improved.

• Journal of the Korean Chemical Society
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• v.66 no.2
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• pp.78-85
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• 2022

Natural white clay was treated with 6 M of H₂SO₄ and heated at 80℃ for 6 h under mechanical stirring and the resulting acid active clay was used as an adsorbent for the removal of Cs⁺ in water. The physicochemical changes of natural white clay and acid active clay were observed by X-ray Fluorescence Spectrometry (XRF), BET Surface Area Analyser and Energy Dispersive X-line Spectrometer (EDX). While activating natural white clay with acid, the part of Al₂O₃, CaO, MgO, SO₃ and Fe₂O₃ was dissolved firstly from the crystal lattice, which bring about the increase in the specific surface area and the pore volume as well as active sites. The specific surface area and the pore volume of acid active clay were roughly twice as high compared with natural white clay. The adsorption of Cs⁺ on acid active clay was increased rapidly within 1 min and reached equilibrium at 60 min. At 25 mg L^- of Cs⁺ concentration, 96.88% of adsorption capacity was accomplished by acid active clay. The adsorption data of Cs⁺ were fitted to the adsorption isotherm and kinetic models. It was found that Langmuir isotherm was described well to the adsorption behavior of Cs⁺ on acid active clay rather than Freundlich isotherm. For adsorption Cs⁺ on acid active clay, the Langmuir isotherm coefficients, Q, was found to be 10.52 mg g^-1. In acid active clay/water system, the pseudo-second-order kinetic model was more suitable for adsorption of Cs⁺ than the pseudo-first-order kinetic model owing to the higher correlation coefficient R² and the more proximity value of the experimental value q_e,exp and the calculated value q_e,cal. The overall results of study showed that acid active clay could be used as an efficient adsorbent for the removal of Cs⁺ from water.

• Journal of the Korean Electrochemical Society
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• v.26 no.1
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• pp.1-10
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• 2023

The cathode, which is one of the four major components of a lithium secondary battery, is an important component responsible for the energy density of the battery. The mixing process of active material, conductive material, and polymer binder is very essential in the commonly used wet manufacturing process of the cathode. However, in the case of mixing conditions of the cathode, since there is no systematic method, in most cases, differences in performance occur depending on the manufacturer. Therefore, LiMn₂O₄ (LMO) cathodes were prepared using a commonly used THINKY mixer and homogenizer to optimize the mixing method in the cathode slurry preparation step, and their characteristics were compared. Each mixing condition was performed at 2000 RPM and 7 min, and to determine only the difference in the mixing method during the manufacture of the cathode other experiment conditions (mixing time, material input order, etc.) were kept constant. Among the manufactured THINKY mixer LMO (TLMO) and homogenizer LMO (HLMO), HLMO has more uniform particle dispersion than TLMO, and thus shows higher adhesive strength. Also, the result of the electrochemical evaluation reveals that HLMO cathode showed improved performance with a more stable life cycle compared to TLMO. The initial discharge capacity retention rate of HLMO at 69 cycles was 88%, which is about 4.4 times higher than that of TLMO, and in the case of rate capability, HLMO exhibited a better capacity retention even at high C-rates of 10, 15, and 20 C and the capacity recovery at 1 C was higher than that of TLMO. It's postulated that the use of a homogenizer improves the characteristics of the slurry containing the active material, the conductive material, and the polymer binder creating an electrically conductive network formed by uniformly dispersing the conductive material suppressing its strong electrostatic properties thus avoiding aggregation. As a result, surface contact between the active material and the conductive material increases, electrons move more smoothly, changes in lattice volume during charging and discharging are more reversible and contact resistance between the active material and the conductive material is suppressed.