• Title/Summary/Keyword: Lithium Electrode

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Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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The Roles of Electrolyte Additives on Low-temperature Performances of Graphite Negative Electrode (전해액 첨가제가 흑연 음극의 저온특성에 미치는 영향)

  • Park, Sang-Jin;Ryu, Ji-Heon;Oh, Seung-Mo
    • Journal of the Korean Electrochemical Society
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    • v.15 no.1
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    • pp.19-26
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    • 2012
  • SEI (solid electrolyte interphase) layers are generated on a graphite negative electrode from three different electrolytes and low-temperature ($-30^{\circ}C$) charge/discharge performance of the graphite electrode is examined. The electrolytes are prepared by adding 2 wt% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) into a standard electrolyte solution. The charge-discharge capacity of graphite electrode shows the following decreasing order; FEC-added one>standard>VC-added one. The polarization during a constant-current charging shows the reverse order. These observations illustrate that the SEI film resistance and charge transfer resistance differ according to the used additives. This feature has been confirmed by analyzing the chemical composition and thickness of three SEI layers. The SEI layer generated from the standard electrolyte is composed of polymeric carbon-oxygen species and the decomposition products ($Li_xPF_yO_z$) of lithium salt. The VC-derived surface film shows the largest resistance value even if the salt decomposition is not severe due to the presence of dense film comprising C-O species. The FEC-derived SEI layer shows the lowest resistance value as the C-O species are less populated and salt decomposition is not serious. In short, the FEC-added electrolyte generates the SEI layer of the smallest resistance to give the best low-temperature performance for the graphite negative electrode.

Initial Charge/Discharge of $LiCoO_2$ Composite Cathode with Various Content of Conductive Material for the Lithium ion Battery (리튬이온전지용 $LiCoO_2$정극의 도전재료에 따른 초기 충방전 특성)

  • Doh Chil-Hoon;Moon Seong-In;Yun Mun-Soo;Yun Suong-Kyu;Yum Duk-Hyung;Park Chun-Jun
    • Journal of the Korean Electrochemical Society
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    • v.2 no.3
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    • pp.123-129
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    • 1999
  • Initial electrochemical characteristics of $LiCoO_2$ electrode for lithium ion battery with various content of super s black as conductive material were evaluated through the charge/discharge with the potential range of 4.3V to 2.0V versus $Li^+/Li^+$. The rate of C/4 and C/2 by the 3 electrode test cell composed with an electrolytic solution of 1 mol/l $LiPF_6/EC+DEC(1:3\;by\; weight)$. Lithium was used as reference electrode. High impedance charge behavior was observed at early stage of charge. In the case of $3\%w/w$ of super s black as conductive material, the specific resistance of the high impedance releasing was $3.82\;{\Omega}\;{\cdot}\;g-LiCoCo_2$ at the current density of $0.5 mA/cm^2$, which corresponds 7 times of the specific resistance of electrode $(0.728 g-LiCoO_2)$. At second charge, the specific resistance of the high impedance releasing was 63 mn · g-Lico02, which corresponds 12eio of the specific resistance of electrode and only $1.7\%$ of that of the first charge. The first charge and discharge specific capacities at C/4 rate were 160-161 and $153\~155mAh/g-LiCoO_2$, respectively, to lead $95.4\~96.4\%$ of coulombic efficiencies and ca. $6 mAh/g-LiCoO_2$ of initial irreversible specific capacity. Specific resistance at the end of charge and rest showed low value at content of super s black between 2 and $7\%w/w$, which agreed with characteristics of irreversible specific capacity. Capacity densities were reduced by the increasing the content of conductive material. They were 447 and 431mAh/ml when 2 and $2.9\%w/w$ of super s black were used, respectively, at the rate of C/4.

A Study on the Resistve Switching Characteristic of Parallel Memristive Circuit of Lithium Ion Based Memristor and Capacitor (리튬 이온 기반 멤리스터 커패시터 병렬 구조의 저항변화 특성 연구)

  • Kang, Seung Hyun;Lee, Hong-Sub
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.4
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    • pp.41-45
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    • 2021
  • In this study, in order to secure the high reliability of the memristor, we adopted a patterned lithium filament seed layer as the main agent for resistive switching (RS) characteristic on the 30 nm thick ZrO2 thin film at the device manufacturing stage. Lithium filament seed layer with a thickness of 5 nm and an area of 5 ㎛ × 5 ㎛ were formed on the ZrO2 thin film, and various electrode areas were applied to investigate the effect of capacitance on filament type memristive behavior in the parallel memristive circuit of memristor and capacitor. The RS characteristics were measured in the samples before and after 250℃ post-annealing for lithium metal diffusion. In the case of conductive filaments formed by thermal diffusion (post-annealed sample), it was not available to control the filament by applying voltage, and the other hand, the as-deposited sample showed the reversible RS characteristics by the formation and rupture of filaments. Finally, via the comparison of the RS characteristics according to the electrode area, it was confirmed that capacitance is an important factor for the formation and rupture of filaments.

Electrochemical Characteristics of CFX Based Lithium Primary Batteries Produced by Carbon Fiber Reinforced Plastic -Derived Waste Carbon Fibers (탄소섬유강화플라스틱 유래 폐 탄소섬유로 제조된 불화탄소 기반 리튬일차전지의 전기화학적 특성)

  • Naeun Ha;Chaehun Lim;Seongmin Ha;Seongjae Myeong;Young-Seak Lee
    • Applied Chemistry for Engineering
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    • v.34 no.5
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    • pp.515-521
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    • 2023
  • In this study, waste carbon fiber obtained by pyrolysis of carbon fiber reinforced plastic (CFRP) was used to produce carbon fluoride through vapor phase fluorination and recycled as a reducing electrode material for lithium primary batteries. First, the physicochemical properties of the waste carbon fiber obtained by pyrolysis were determined, and the structural and chemical properties of carbon fluoride were analyzed to evaluate the effect of vapor phase fluorination on the waste carbon fiber. XRD analysis confirmed that the hexagonal network carbon laminated structure (002 peak) of the waste carbon fiber was gradually converted into a carbon fluoride structure (CFX, 001 peak) as the temperature of gas phase fluorination increased. The discharge capacity of the lithium primary battery produced using this carbon fluoride was up to 862 mAh/g. This was compared to the discharge capacity of carbon fluoride-based Li-ion batteries made of other carbon materials. These results suggest that carbon fluoride made from waste CFRP-based carbon fibers can be used as a reducing electrode material for Li-ion batteries.

Electrolyte-Concentration Effects on Interfacial Reactions Between Lithium Negative Electrode and Electrolyte (리튬금속 음극/전해질 계면반응에 미치는 전해질 농도의 영향)

  • Seo, Hee-Young;Jeong, Soon-Ki
    • Proceedings of the KAIS Fall Conference
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    • 2007.11a
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    • pp.353-355
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    • 2007
  • 본 논문에서는 리튬금속을 음극으로 하는 반전지에 여러 농도의 전해질을 사용하여 그에 따른 충/방전 효율과, 음극 표면을 관찰하는 것에 의해 전해질 농도가 음극/전해질 계면반응에 어떠한 영향을 끼치는지 알아보았다. 또한 X-ray Photoelectron Spectroscopy(XPS)를 사용하여 표면에 생성되는 물질의 조성과 구조를 해석하였다.

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A Self-standing and Binder-free Electrodes Fabricated from Carbon Nanotubes and an Electrodeposited Current Collector Applied in Lithium-ion Batteries

  • Luais, Erwann;Mery, Adrien;Abou-Rjeily, John;Sakai, Joe;Tran-Van, Francois;Ghamouss, Fouad
    • Journal of Electrochemical Science and Technology
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    • v.10 no.4
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    • pp.373-380
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    • 2019
  • In this paper, we report the preparation of a flexible, self-standing and binder-free carbon nanotubes (CNTs) electrode with an electro-generated current collector. The copper current collector layer was electrodeposited on the backside of CNTs self-standing film obtained by a simple filtration process. The obtained CNTs-Cu assembly was used as a negative electrode in Li-ion batteries exhibiting good performance along with proving its applicability in flexible batteries.