• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.350-351
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• 2005

The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

• Journal of Electrochemical Science and Technology
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• v.6 no.2
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• pp.50-58
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• 2015

There is a great deal of current interest in the development of rechargeable batteries with high energy storage capability due to an increasing demand for electric vehicles (EVs) with driving ranges comparable to those of gasoline-powered vehicles. Among various types of batteries under development, a Li-O₂ battery delivers the highest theoretical energy density; thus, it is considered a promising energy storage technology for EV applications. Despite the fact that extensive research efforts have been made in the field of Li-O₂ batteries in recent years, there are still many technical challenges to be addressed, such as low round-trip efficiency, poor reversibility, and poor power capability. In this article, we provide a short review on the fundamental electrochemistry of Li-O₂ batteries with non-aqueous electrolytes and on electrode materials that have been employed in cathodes (oxygen electrodes). The major aim of this mini-review is to highlight the physical and electrochemical origins of scientific challenges facing Li-O₂ battery technology and to overview the strategies proposed to overcome them.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3221-3224
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• 2010

This study investigates the requirements of lithium-air cathodes, which directly influence discharge capacity. The cathodes of Li-air cell are made by using five different carbon materials, such as Ketjen black EC600JD, Super P, Ketjen black EC300JD, Denka black, and Ensaco 250G. The Ketjen black EC600JD provides discharge capacity of 2600 mAh/g per carbon weight, while that of Ensaco 250G shows only 579 mAh/g. To figure out the differences of discharge capacity from carbon materials, their surface area and pore volume are analyzed. These are found out to be the critical factors in determining discharge capacity. Furthermore, carbon loading on Ni foam and amounts of electrolyte are significant factors that affect discharge capacity. In order to investigate catalyst effect, electrolytic manganese dioxide (EMD) is incorporated and delivered 4307 mAh/g per carbon weight. This infers that EMD facilitates to break $O_2$ interactions and leads to enhance discharge capacity.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1737-1741
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• 2008

The electrochemical and thermal stability of $LiNi_{0.8}Co_{0.16}Al_{0.04}O_2$ were studied before and after $Co_3(PO_4)_2$ coating. Different to conventional coating material such as $ZrO_2$ or AlPO4, the coating layer was not detected clearly by TEM analysis, indicating that the $Co_3(PO_4)_2$ nanoparticles effectively reacted with surface impurities such as $Li_2CO_3$. The coated sample showed similar capacity at a low C rate condition. However, the rate capability was significantly improved by the coating effect. It is associated with a decrease of impedance after coating because impedance can act as a major barrier for overall cell performances in high C rate cycling. In the DSC profile of the charged sample, exothermic peaks were shifted to high temperatures and heat generation was reduced after coating, indicating the thermal reaction between electrode and electrolyte was sucessfully suppressed by $Co_3(PO_4)_2$ nanoparticle coating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.347-350
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• 2000

The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li polymer battery. The temperature dependence of conductivity, impedance spectroscopy and electrochemical properties of PMMA/PVDF electrolytes as a function of a mixed ratio were reported for PMMA/PVDF based polymer electrolyte films, which were prepared by thermal gellification method of preweighed PMMA/PVDF, plasticizer and Li salt. The ion conductivity of PMMA/PVDF electrolytes was 10$\^$-3/S/cm, which may be applicable to a constituent of lithium secondary battery. 5PMMA20PVDFLiC1O$_4$PC$\sub$8/EC$\sub$8/ electrolyte remains stable up to 5V vs. Li/Li$\^$+/. Steady state current method and AC impedance were used for the determination of transference numbers in PMMA/PVDF electrolyte film. The transference number of 5PMMA20PVDFLiC1O$_4$PC$\sub$8/EC$\sub$8/ electrolyte is 0.55.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.341-348
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• 2019

This paper reports the microstructure and electrochemical properties of Si-Al-Fe ternary amorphous alloys prepared by rapid solidification as an anode for lithium secondary batteries. The microstructure was analyzed using XRD and HR-TEM with EDS mapping. In accordance with DSC analysis, annealing was performed to crystallize the active nano-Si in the amorphous alloy. Thus, nano-Si forms (~80 nm) embedded in the matrix alloy, such as $Fe_2Al_3Si_3$, $FeSi_2$, and $Fe_{0.42}Si_{2.67}$, were successfully synthesized. The electrode based on the Si-Al-Fe ternary alloy delivered an initial discharge capacity of approximately $700mAh^{g-1}$, and exhibited a high Coulombic efficiency of 99.0~99.6% from the $2^{nd}$ to $70^{th}$ cycles.

• Journal of Electrochemical Science and Technology
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• v.10 no.1
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• pp.55-60
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• 2019

Herein, the effect of counter anions on the formation of a solid electrolyte interphase (SEI) in a propylene carbonate (PC)-based electrolyte solution was investigated. Although the reversible capacities were different, reversible intercalation and de-intercalation of lithium ions occurred in the graphite negative electrode in the PC-based electrolyte solutions containing 1 M $LiClO_4$, $LiPF_6$, $LiBF_4$, and $LiCF_3SO_3$ at low temperature ($-15^{\circ}C$). This indicated that the surface films acted as an effective SEI to suppress further co-intercalation and decomposition reactions at low temperature. However, the SEIs formed at the low temperature were unstable in 1 M $LiPF_6$ and $LiBF_4/PC$ at room temperature ($25^{\circ}C$). On the other hand, increasing reversible capacity was confirmed in the case of $LiCF_3SO_3/PC$ at room temperature, because the SEI formed at the low temperature was still maintained. These results suggest that counter anions are an important factor to consider for the formation of effective SEIs in PC-based electrolyte solutions.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.1-20
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• 2021

In-depth knowledge of electrode processes is crucial for determining the electrochemical performance of lithium-ion batteries (LIBs). In particular, the conduction mechanisms of charged species in the electrodes, such as lithium ions (Li+) and electrons, are directly correlated with the performance of the battery because the overall reaction is dependent on the charge transport behavior in the electrodes. Therefore, it is necessary to understand the different electrochemical processes occurring in electrodes in order to elucidate the charge conduction phenomenon. Thus, it is essential to conduct fundamental studies on electrochemical processes to resolve the technical challenges and issues arising during the ionic and electronic conduction. Furthermore, it is also necessary to understand the transport of charged species as well as the predominant factors affecting their transport in electrodes. Based on such in-depth studies, potential approaches can be introduced to enhance the mobility of charged entities, thereby achieving superior battery performances. A clear understanding of the conduction mechanism inside electrodes can help overcome challenges associated with the rapid movement of charged species and provide a practical guideline for the development of advanced materials suitable for high-performance LIBs.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.159-166
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• 2022

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g^-1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g^-1, shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

• Journal of the Korean institute of surface engineering
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• v.57 no.2
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• pp.115-124
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• 2024

In advancing Li-ion battery (LIB) technology, the solid electrolyte interface (SEI) layer is critical for enhancing battery longevity and performance. Formed during the charging process, the SEI layer is essential for controlling ion transport and maintaining electrode stability. This research provides a detailed analysis of how vinylene carbonate (VC) influences SEI layer formation. The integration of VC into the electrolyte markedly improved SEI properties. Moreover, correlation analysis revealed a connection between electrolyte decomposition and battery degradation, linked to the EMC esterification and dicarboxylate formation processes. VC facilitated the formation of a more uniform and chemically stable SEI layer enriched with poly(VC), thereby enhancing mechanical resilience and electrochemical stability. These findings deepen our understanding of the role of electrolyte additives in SEI formation, offering a promising strategy to improve the efficiency and lifespan of LIBs.