• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.112-121
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• 2019

In this study, silicon / carbon nanotube / carbon composite particles with high capacity were fabricated by using micro-sized silicon particles and carbon nanotubes as an anode material for lithium ion batteries. The silicon / carbon nanotube / carbon composite particles were prepared by spray drying method to prepare spherical composite particles. The composite particles have the network structure of the carbon nanotubes around the silicon particles, in which the silicon particles and the carbon nanotubes are bonded by amorphous carbon. It appears that the volume expansion of silicon is effectively buffered and the electrical contact is maintained in the network structure of the composite particles during charge-discharge cycles.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.346-357
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• 2021

In recent years, supercapacitors have been developed rapidly as a rechargeable energy storage device. And the performance of supercapacitors is depending on electrode materials, the preparation method and performance of electrode materials have become the primary goal of scientific development. This study synthesizes Co₃O₄@MnO₂@PPy cathode material with porous pattern core-shell structure by hydrothermal method and electrodeposition. The result samples are characterized by X-ray diffraction transmission/scanning electron microscope, and X-ray photoelectron spectroscopy. Electrochemical evaluation reveals that electrochemical performance is significantly enhanced by PPy depositing. The specific capacitance of Co₃O₄@MnO₂@PPy is 977 F g^-1 at 1 A g^-1, the capacitance retention rate of 105%. Furthermore, the electrochemical performance of Co₃O₄@MnO₂@PPy//AC asymmetric supercapacitor assembles with AC as the negative electrode material is significantly better than that of MnO₂//AC and Co₃O₄@MnO₂//AC. The capacity of Co₃O₄@MnO₂@PPy//AC is 102.78 F g^-1. The capacity retention rate is still 120% for 5000 charge-discharge cycles.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.28-32
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• 2023

Recently, the use of stable lithium nanostructures as substrates and electrodes for secondary batteries can be a fundamental alternative to the development of next-generation system semiconductor devices. However, lithium structures pose safety concerns by severely limiting battery life due to the growth of Li dendrites during rapid charge/discharge cycles. Also, enabling long cyclability of high-voltage oxide cathodes is a persistent challenge for all-solid-state batteries, largely because of their poor interfacial stabilities against oxide solid electrolytes. For the development of next-generation system semiconductor devices, solid electrolyte nanostructures, which are used in high-density micro-energy storage devices and avoid the instability of liquid electrolytes, can be promising alternatives for next-generation batteries. Nevertheless, poor lithium ion conductivity and structural defects at room temperature have been pointed out as limitations. In this study, a low-dimensional Graphene Oxide (GO) structure was applied to demonstrate stable operation characteristics based on Li+ ion conductivity and excellent electrochemical performance. The low-dimensional structure of GO-based solid electrolytes can provide an important strategy for stable scalable solid-state power system semiconductor applications at room temperature. The device using uncoated bare NCA delivers a low capacity of 89 mA h g-1, while the cell using GO-coated NCA delivers a high capacity of 158 mA h g−1 and a low polarization. A full Li GO-based device was fabricated to demonstrate the practicality of the modified Li structure using the Li-GO heterointerface. This study promises that the lowdimensional structure of Li-GO can be an effective approach for the stabilization of solid-state power system semiconductor architectures.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.7-12
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• 2014

There is increasing demand on the reducing the weight and the volume of the major components in lithium secondary battery to improve energy density. Separator not only provides pathway for lithium ion movement but also prevents direct contact between anode and cathode. Herein we fabricated polyethylene separator by varying biaxial stretching ratio to obtain membrane thickness of 16, 12, and $9{\mu}m$. Mechanical and thermal properties of the separator with different thickness were investigated. Also rate capability and charge-discharge cycle property up to 500 cycles were studied using coin type full-cell with $LiCoO_2$ and graphite as a cathode and an anode, respectively. All the cells using separator with different thickness demonstrated excellent capacity retention after 500cycles (around 80%). Considering the rate capability, cell using separator with thickness of $9{\mu}m$ showed best performance. Interestingly, separator thickness of $9{\mu}m$ was more resistant to heat contraction compared to that of $16{\mu}m$ separator.

• Journal of the Korean Electrochemical Society
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• v.6 no.4
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• pp.229-235
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• 2003

A precursor of lithium manganese oxide was synthesized by mixing $(CH_3)_2CHOLi\;with\;Mn(CH_3COO)_2{\cdot}4H_2O$ in ethanol using a sol-gel method, then heat-treated at $400^{\circ}C\;and\;800^{\circ}C$ in air atmosphere. The condition of heat treatment was determined by thermogravimetric analysis/differential thermogravimetric analysis (TGA/DTA). The characterization of the lithium manganese oxide was done by X-ray diffraction (XRD) spectra and scanning electron microscopy (SEM). The electrochemical characteristics of lithium manganese oxide electrode for lithium ion battery were measured by cyclic voltammetry (CV), chronoamperometry and AC impedance method using constant charge/discharge process. The electrochemical behaviors of the electrode have been investigated in a 1.0M $LiClO_4/propylene$ carbonate electrolyte solution. The diffusivity of lithium ions, $D^+\;_{Li}\;^+$, as determined by AC impedance technique was $6.2\times10^{-10}cm^2s^{-1}$.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.143-149
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• 2015

Carbon-coated $Li_2MnSiO_4$ powders as the active materials for the cathode were synthesized by planetary ball milling and solid-state reaction, and their phase formation behavior and charge-discharge properties were investigated. Calcination temperature and atmosphere were controlled in order to obtain the ${\beta}-Li_2MnSiO_4$ phase, which was active electrochemically, and the carbon-coated $Li_2MnSiO_4$ active material powders with near single phase ${\beta}-Li_2MnSiO_4$ could be fabricated. The particles of the synthesized powders were secondary particles composed of primary ones of about 100 nm size. The carbon incorporation was essential to enable the Li ions to be inserted and extracted from $Li_2MnSiO_4$ active materials, and the initial capacity of 192 mAh/g could be obtained in the $Li_2MnSiO_4$ active materials with 4.8 wt% of carbon.

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.16-21
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• 2011

$Li_4Sn_xTi_{5-x}O_{12}$ was manufactured by high energy ball milling (HEBM) and used as an anode material for lithium ion battery. Various amount of $SnO_2$was added to $Li_4Ti_5O_{12}$ and heated at different temperatures. The purpose of this research was to see the effect of $SnO_2$ addition into $Li_4Ti_5O_{12}$. Manufactured samples were analyzed by TGA, XRD, SEM, PSA. Battery cycler was used to test the charge/discharge properties of active materials. Heat treatment temperature of $800^{\circ}C$ was needed to make a stable structure of $Li_4Sn_xTi_{5-x}O_{12}$ and the particle size distribution was $0.2{\sim}0.6\;{\mu}m$. Charge/discharge process was repeated for 50 cycles at room temperature. The initial capacity was 168mAh/g and the voltage plateau was observed at 1.55V(Li/$Li^+$).

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.529-533
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• 2023

The fundamental electrochemical properties and adsorption capabilities of the carbonized product derived from coffee grounds, a prevalent form of lignocellulose abundantly generated in our daily lives, have been extensively investigated. The structure and morphology of the resultant carbonized product, obtained through a carbonization process conducted at a relatively low temperature of 600 ℃, were meticulously examined using a scanning electron microscope. Raman spectroscopy measurements yielded a relative crystallinity (D/G ratio) of the carbon product of 0.64. Electrical measurements revealed a linear ohmic relationship within the carbonized product. Furthermore, the viability of utilizing this carbonized material as an anode in lithium-ion batteries was evaluated through half-cell charge/discharge experiments, demonstrating an initial specific capacity of 520 mAh/g. Additionally, the adsorption performance of the carbon material towards a representative dye molecule was assessed via UV spectroscopy analyses. Supplementary experiments corroborated the material's ability to adsorb a distinct model molecule characterized by differing surface polarity, achieved through surface modification. This article presents pivotal findings that hold substantial implications for forthcoming research endeavors centered around the recycling of lignocellulose waste.

• Journal of the Korean Electrochemical Society
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• v.27 no.3
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• pp.88-96
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• 2024

Lithium metal has garnered attention as a promising anode active material thanks to its high specific capacity, energy density, and the lowest reduction potential. However, the formation of dendrites, dendritic crystals that arise during the charge and discharge process, has posed safety and lifetime stability challenges. To resolve this, our study has introduced a novel separator design. This separator features a composite coating of vapor-grown carbon fiber, a conductive material in nanofibers, and silver. We have meticulously studied the impact of this innovative separator on the electrochemical properties of the lithium metal anode, unveiling promising results. To confirm the synergistic effect of VGCF and Ag, a separator with no surface treatment and a separator with only VGCF coated on one side were prepared and compared with the Ag-VGCF-separator. In the case of the bare separator, the Li metal surface is covered with dendrites during the initial charge and discharge process. In contrast, both the VGCF-separator and the Ag-VGCF-separator show Li precipitation inside the conductive coating layer coated on the separator surface. Additionally, the Ag-VGCF-separator showed a more uniform precipitate shape than the VGCF-separator. As a result, the Ag-VGCF-separators show improved electrochemical properties compared to the bare separators and the VGCF-separators.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.191-198
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• 2018

SnSb alloy powders with excess Sn or Sb are fabricated by the high energy ball-milling of pure Sn and Sb powders with different Sn/Sb molar ratios, and then their material properties and lithium electrochemical performances are investigated. It is revealed by X-ray diffraction that SnSb alloys are successfully synthesized, and the powder size is decreased via ball-milling. Charge-discharge test using a coin-cell shows that the best result, in terms of the cyclability and the capacity after 50 cycles, comes from the electrode composed of Sn : Sb = 4 : 6, i.e. the capacity of $580mAh\;g^{-1}$ after 50 cycles. When the electrode is composed of Sn : Sb = 3 : 7, however, the capacity is noticeably decreased by the restrained Sn reaction with Li-ion. The pure SnSb alloy powders (Sn : Sb = 5 : 5) results in the second best performance. In the case of Sn-rich SnSb alloys, the initial capacity is relatively high, but the capacity is quickly fading after 20 cycles.