• Title, Summary, Keyword: Cathode material

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The Influence of the Cathode Surface State on the Spark Voltage in the Townsend Discharge Domain (Townsend 방전영역의 불꽃전압에 미치는 음극표면상태의 영향)

  • 백용현
    • 전기의세계
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    • v.28 no.1
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    • pp.73-82
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    • 1979
  • There are a great number of papers on the Townsend discharge in gases, and many of them are concerned with the effect of the cathode. It has been regarded that there are two kinds of effect of the electrodes, especially of the cathode; (a) the effect caused by the difference of the cathode material and (b) the effect by the change of the cathode surface state even in the same material. Both of them may change the secondary coefficient following after the change of the work function, and the atter may further change the primary ionization coefficient as foreign atoms on the surface may be dseorbed in sparks to decrease the purity of the gas. Thus the two effects must be investigated independently to study the roles of the cathode in gas discharges. In this report the effect of the cathode material on the sparking voltage is described. The experiment is also carried out under the condition that the desorption of impurities from the cathode be negligible. From these the new correlativity between the work function of the cathode and the sparking voltage is obtained. In addition, the interesting character of the minimum point of the Paschen's curve can be found.

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Triphenyl phosphate as an Efficient Electrolyte Additive for Ni-rich NCM Cathode Materials

  • Jung, Kwangeun;Oh, Si Hyoung;Yim, Taeeun
    • Journal of Electrochemical Science and Technology
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    • v.12 no.1
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    • pp.67-73
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    • 2021
  • Nickel-rich lithium nickel-cobalt-manganese oxides (NCM) are viewed as promising cathode materials for lithium-ion batteries (LIBs); however, their poor cycling performance at high temperature is a critical hurdle preventing expansion of their applications. We propose the use of a functional electrolyte additive, triphenyl phosphate (TPPa), which can form an effective cathode-electrolyte interphase (CEI) layer on the surface of Ni-rich NCM cathode material by electrochemical reactions. Linear sweep voltammetry confirms that the TPPa additive is electrochemically oxidized at around 4.83 V (vs. Li/Li+) and it participates in the formation of a CEI layer on the surface of NCM811 cathode material. During high temperature cycling, TPPa greatly improves the cycling performance of NCM811 cathode material, as a cell cycled with TPPa-containing electrolyte exhibits a retention (133.7 mA h g-1) of 63.5%, while a cell cycled with standard electrolyte shows poor cycling retention (51.3%, 108.3 mA h g-1). Further systematic analyses on recovered NCM811 cathodes demonstrate the effectiveness of the TPPa-based CEI layer in the cell, as electrolyte decomposition is suppressed in the cell cycled with TPPa-containing electrolyte. This confirms that TPPa is effective at increasing the surface stability of NCM811 cathode material because the TPPa-initiated POx-based CEI layer prevents electrolyte decomposition in the cell even at high temperatures.

Designing of a Novel Core-Shell-Structured Co-free Cathode Material with Enhanced Thermal and Structural Stability for Lithium Ion Batteries

  • Shin, Ji-Woong;Nam, Yun-Chae;Son, Jong-Tae
    • Journal of the Korean Electrochemical Society
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    • v.22 no.4
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    • pp.172-176
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    • 2019
  • The first commercialized cathode material, $LiCoO_2$, suffers from disadvantages such as high cost and toxicity and also possesses safety problems. The nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material, used as an alternative to $LiCoO_2$, has highly reversible capacity and high energy density. So, the nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material is widely used as an alternative to $LiCoO_2$ due to its highly reversible capacity and high energy density. However, $LiNi_{0.9}Mn_{0.1}O_2$ has several disadvantages as well, such as poor cycle performance and poor thermal instability. To address these problems, we synthesized a new material, $LiNi_{0.5}Mn_{0.5}O_2$, as a shell on the surface of a core to suppress the surface degradation. The new material showed high structural and thermal stabilities and could also maintain a high capacity. The capacity retention of the core-shell cathode (87.7%) was better than that of the core cathode (76.9%) after 50 cycles. Analysis using differential scanning calorimetry revealed that the heat generation in the core-shell cathode ($65.9Jg^{-1}$) was lower than that in the core cathode ($559.7Jg^{-1}$).

The influence of cathode material on the stability of organic photovoltaics (Cathode material에 따른 organic photovoltaics 안정성의 영향)

  • Park, Jun-Ki;Kim, Yong-Hoon;Han, Jeong-In
    • Proceedings of the KIEE Conference
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    • pp.1266-1267
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    • 2011
  • We studied the influence of cathode material on the stability of organic phtovoltaics (OPVs). OPVs with LiF/Al and Ag/Ca/Ag cathode were fabricated and the stability were evaluated. The sample with LiF/Al cathode showed efficiency degradation from 2.42% to 2.04% during 50 days. On the other hand, the sample with Ag/Ca/Ag cathode showed more steeper efficiency degradation from 2.38% to 0.80% during 50 days. The different of degradation can be attributed to a larger increase of series resistance ($R_s$) in Ag/Ca/Ag cathode sample.

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High-Rate Blended Cathode with Mixed Morphology for All-Solid-State Li-ion Batteries

  • Heo, Kookjin;Im, Jehong;Lee, Jeong-Seon;Jo, Jeonggeon;Kim, Seokhun;Kim, Jaekook;Lim, Jinsub
    • Journal of Electrochemical Science and Technology
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    • v.11 no.3
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    • pp.282-290
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    • 2020
  • In this article, we report the effect of blended cathode materials on the performance of all-solid-state lithium-ion batteries (ASLBs) with oxide-based organic/inorganic hybrid electrolytes. LiFePO4 material is good candidates as cathode material in PEO-based solid electrolytes because of their low operating potential of 3.4 V; however, LiFePO4 suffers from low electric conductivity and low Li ion diffusion rate across the LiFePO4/FePO4 interface. Particularly, monoclinic Li3V2(PO4)3 (LVP) is a well-known high-power-density cathode material due to its rapid ionic diffusion properties. Therefore, the structure, cycling stability, and rate performance of the blended LiFePO4/Li3V2(PO4)3 cathode material in ASLBs with oxidebased inorganic/organic-hybrid electrolytes are investigated by using powder X-ray diffraction analysis, field-emission scanning electron microscopy, Brunauer-Emmett-Teller sorption experiments, electrochemical impedance spectroscopy, and galvanostatic measurements.

Recovery of Rare Metals from the Waste Secondary Lithium Ion Battery Cathode Active Materials Using Lactic Acid and Oxalic acid (젖산과 옥살산을 이용한 폐 이차 리튬이온 전지 양극 활물질로부터 희유금속들의 회수)

  • Kim, Younjung;Han, Ji Sun;Choi, Sik Young;Oh, In-Gyung;Hong, Yong Pyo;Ryoo, Keon Sang
    • Journal of the Korean Chemical Society
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    • v.63 no.6
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    • pp.446-452
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    • 2019
  • We have developed a method that can leach Co, Mn, and Ni in the cathode active material safely using lactic acid. When cathode active material was leached by lactic acid, lactic acid showed the highest efficiency at 2 N than 1 N and above 4 N concentration. When the cathode active material was added incrementally into the solution of lactic acid, the maximum solubility was 30 g/L at 2 N concentration. Oxalic acid was added in the solution of lactic acid and it showed that rare metals represent the most economical recovery efficiency at 4 g/L. Based on this study, it was found that the optimal condition for recovery of rare metals from cathode active material is oxalic acid : cathode active material = 7 : 1 as a ratio of weight. In addition, it was observed that the precipitate produced by oxalic acid is a polynuclear crystalline material bonded with 3 components of Co, Ni, and Mn.

Characterization of (Co/Nb)-coated NiO as a Cathode Material for Molten Carbonate Fuel Cells (코발트와 나이오븀이 코팅된 NiO 용융탄산염 연료전지 양극물질 특성 연구)

  • Choi, Hee-Seon;Yi, Cheol-Woo;Kim, Keon
    • Journal of the Korean Electrochemical Society
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    • v.13 no.3
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    • pp.203-210
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    • 2010
  • NiO is commonly used as the cathode for the molten carbonate fuel cell due to its stability and high electrical conductivity in molten carbonates and oxygen atmosphere. However, long-term operation of MCFC has a serious problem which is the degradation of cathode material, the so-called Ni dissolution. In the present study, we have attempted to synthesize a new alternative cathode material as Co/Nb-coated NiO cathode. The results obtained in this study suggest that the Co/Nb-coated NiO cathode can be utilized as having lower dissolution and higher cell performance than those of the pure NiO cathode.

Thin films made by magnetron sputtering cathode with wide target erosion (고효율 마그네트론 스퍼트링 캐소드의 설계 및 박막 제작 특성)

  • Park, Jang-Sick;Lee, Won-Geon;Jung, Min-Gi;Park, Lee-Soon;An, Chang-Ku
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.365-366
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    • 2007
  • High quality cathode with high deposition rate of thin films and long target life time is required for manufacturing TFT-LCD and semiconductor. We developed WV(wide view) sputtering cathode with wide erosion area and high deposition rate. Ti thin film thickness variation in WV cathode is below 5% for 380 kWh target life time. Al thin film thickness using normal cathode is decreased about 20%. By using WV cathode, target using efficiency was improved 40%. in comparison with normal cathode.

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Effect of substituent and dopant on properties of $LiMn_2O_4$ as cathode materials for lithium ion secondary batteries

  • Lee, Dae-Jin;Wai, Yin-Loo;Jee, Mi-Jung;Bae, Hyun;Choi, Byung-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.294-294
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    • 2007
  • Spinel cathode material $LiMn_2O_4$ is currently studied as a promising cathode material for lithium ion secondary batteries for future applications because of it is low cost, easy to be prepared and capable to be operated in high voltage range. However as a cathode material, $LiMn_2O_4$ performs a poor capacity retention which leads to short cycle life. In this study, stoichiometric $LiMn_2O_4$ was synthesized with granulation method with ion substitution to stabilize its structure and niobium doping to improve its conductivity. These well-mixed powders were calcined at $850^{\circ}C$ for 6 hours and its properties were investigated. Correlations of dopant and electrochemical properties were examined as well.

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The Effects of Li-La-Ti-O Coating on the Properties of Li[Ni0.3Co0.4Mn0.3]O2 Cathode Material (Li[Ni0.3Co0.4Mn0.3]O2 양극물질의 Li-La-Ti-O코팅 효과)

  • Lee, Hye-Jin;Yun, Su-Hyun;Park, Bo-Gun;Ryu, Jea-Hyeok;Kim, Kwan-Su;Kim, Seuk-Buom;Park, Yong-Joon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.10
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    • pp.890-896
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    • 2009
  • Li(Ni, Co, Mn)$O_2$ has been known as one of the most promising cathode materials for lithium secondary batteries. However, it has some problems to overcome for commercialization such as inferior rate capability and unstable thermal stability. In order to address these problems, surface modification of cathode materials by coating has been investigated. In the coating techniques, selection of coating material is a key factor of obtaining enhanced properties of cathode materials. In this work, we introduced solid electrolyte (Li-La-Ti-O) as a coating material on the surface of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode. Specially, we focused on a rate performance of Li-La-Ti-O coated $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode. Both bare and Li-La-Ti-O 2 wt.% coated sample showed similar discharge capacity at 0.5C rate. However, as the increase of charge-discharge rate to 3C, the coated samples displayed better discharge capacity and cyclic performance than those of bare sample.