• Title/Summary/Keyword: cathode interfacial layer

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Pyromellitic dianhydride as a cathode interfacial layer in the organic light emitting diodes: thickness optimization and its electroluminescent characteristics

  • Nam, Eun-Kyoung;Moon, Mi-Ran;Son, Dong-Jin;Park, Keun-Hee;Jung, Dong-Geun;Kim, Hyoung-Sub
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.837-838
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    • 2009
  • In this work, pyromellitic dianhydride (PMDA) was used as a cathode interfacial layer in the organic light emitting diodes (OLEDs) and its thickness was optimized. Various electrical and optical characterizations of the OLEDs having various thicknesses of the PMDA cathode interfacial layer revealed that the best OLED performance could be achieved by using 0.5 nm-thick PMDA layer compared to the control device without any interfacial layer.

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Stabilizing Li2O-based Cathode/Electrolyte Interfaces through Succinonitrile Addition

  • Myeong Jun Joo;Yong Joon Park
    • Journal of Electrochemical Science and Technology
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    • v.14 no.3
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    • pp.231-242
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    • 2023
  • Li2O-based cathodes utilizing oxide-peroxide conversion are innovative next-generation cathodes that have the potential to surpass the capacity of current commercial cathodes. However, these cathodes are exposed to severe cathode-electrolyte side reactions owing to the formation of highly reactive superoxides (Ox-, 1 ≤ x < 2) from O2- ions in the Li2O structure during charging. Succinonitrile (SN) has been used as a stabilizer at the cathode/electrolyte interface to mitigate cathode-electrolyte side reactions. SN forms a protective layer through decomposition during cycling, potentially reducing unwanted side reactions at the interface. In this study, a composite of Li2O and Ni-embedded reduced graphene oxide (LNGO) was used as the Li2O-based cathode. The addition of SN effectively thinned the interfacial layer formed during cycling. The presence of a N-derived layer resulting from the decomposition of SN was observed after cycling, potentially suppressing the formation of undesirable reaction products and the growth of the interfacial layer. The cell with the SN additive exhibited an enhanced electrochemical performance, including increased usable capacity and improved cyclic performance. The results confirm that incorporating the SN additive effectively stabilizes the cathode-electrolyte interface in Li2O-based cathodes.

Electrochemical Properties of Cathode according to the Type of Sulfide Electrolyte and the Application of Surface Coating

  • Yoon, Da Hye;Park, Yong Joon
    • Journal of Electrochemical Science and Technology
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    • v.12 no.1
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    • pp.126-136
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    • 2021
  • The electrochemical performance of all-solid-state cells (ASSCs) based on sulfide electrolytes is critically affected by the undesirable interfacial reactions between oxide cathodes and sulfide electrolytes because of the high reactivity of sulfide electrolytes. Based on the concept that the interfacial reactions are highly dependent on the type of sulfide electrolyte, the electrochemical properties of the ASSCs prepared using three types of sulfide electrolytes were observed and compared. The Li2MoO4-LiI coating layer was also introduced to suppress the interfacial reactions. The cells using argyrodite electrolyte exhibited a higher capacity and Coulombic efficiency than the cells using 75Li2S-22P2S5-3Li2SO4 and Li7P3S11 electrolytes, indicating that the argyrodite electrolyte is less reactive with cathodes than other electrolytes. Moreover, the introduction of Li2MoO4-LiI coating on the cathode surface significantly enhanced the electrochemical performance of ASSCs because of the protection of coating layer. Pulverization of argyrodite electrolyte is also effective in increasing the capacity of cells because the smaller size of electrolyte particles improved the contact stability between the cathode and the sulfide electrolyte. The cyclic performance of cells was also enhanced by pulverized electrolyte, which is also associated with improved contact stability at the cathode/electrolyte. These results show that the introduction of Li2MoO4-LiI coating and the use of pulverized sulfide electrolyte can exhibit a synergic effect of suppressed interfacial reaction by the coating layer and improved contact stability owing to the small particle size of electrolyte.

Interfacial Engineering of Polymer Light Emitting Diode

  • Chen, Show-An
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08a
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    • pp.165-167
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    • 2007
  • The performance of polymer light emitting diode can be improved significantly by interfacial engineering on anode and/or cathode through adjusting the charge injection barriers for holes and electrons. Studies involve CFx and SAM modifications on ITO, thickness and delay time to baking of PEDOT:PSS, and electron injection/hole blocking layer.

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Enhanced Electrochemical Properties of All-Solid-State Batteries Using a Surface-Modified LiNi0.6Co0.2Mn0.2O2 Cathode

  • Lim, Chung Bum;Park, Yong Joon
    • Journal of Electrochemical Science and Technology
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    • v.11 no.4
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    • pp.411-420
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    • 2020
  • Undesirable interfacial reactions between the cathode and sulfide electrolyte deteriorate the electrochemical performance of all-solid-state cells based on sulfides, presenting a major challenge. Surface modification of cathodes using stable materials has been used as a method for reducing interfacial reactions. In this work, a precursor-based surface modification method using Zr and Mo was applied to a LiNi0.6Co0.2Mn0.2O2 cathode to enhance the interfacial stability between the cathode and sulfide electrolyte. The source ions (Zr and Mo) coated on the precursor-surface diffused into the structure during the heating process, and influenced the structural parameters. This indicated that the coating ions acted as dopants. They also formed a homogenous coating layer, which are expected to be layers of Li-Zr-O or Li-Mo-O, on the surface of the cathode. The composite electrodes containing the surface-modified LiNi0.6Co0.2Mn0.2O2 powders exhibited enhanced electrochemical properties. The impedance value of the cells and the formation of undesirable reaction products on the electrodes were also decreased due to surface modification. These results indicate that the precursor-based surface modification using Zr and Mo is an effective method for suppressing side reactions at the cathode/sulfide electrolyte interface.

Novel Water-Soluble Polyfluorenes as an Interfacial layer leading to Cathodes-Independent High Performance of Organic Solar Cells

  • Oh, Seung-Hwan;Shim, Hee-Sang;Park, Dong-Won;Jeong, Yon-Kil;Lee, Jae-Kwang;Moon, Seung-Hyeon;Kim, Dong-Yu
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.394-394
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    • 2009
  • Water solubility of conjugated polymers may offer many applications. Potential applications of water-soluble conjugated polymers include the polymer light-emitting diode and new materials for nano and micro hollow-capsules, and bio- or chemo-sensors. We synthesized neutral polyfluorenes containing bromo-alkyl groups by the palladium catalyzed Suzuki coupling reaction. Bromo-alkyl side groups in neutral polyfluorenes were quaternized by tri-methyl amine solution. The electrochemical and optical properties of water-soluble conjugated polymers are discussed. This novel synthesized water-soluble conjugated polymers were used as a interfacial dipole layer between active layer and metal cathode in polymer solar cell for enhancement of open-circuit voltage (Voc), which is one of the most critical factors in determining device characteristics. We also investigated the device performance of polymer solar cell with different metal cathode such as Al, Ag, Au and Cu. In polymer solar cell, novel cationic water-soluble conjugated polymers were inserted between active layer and high-work function cathode (Al, Ag, Au and Cu).

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Cathode Microstructure Control and Performance Improvement for Low Temperature Solid Oxide Fuel Cells (저온 고체산화물 연료전지용 공기극 미세구조 제어 및 성능개선)

  • Kang, Jung-Koo;Kim, Jin-Soo;Yoon, Sung-Pil
    • Journal of the Korean Ceramic Society
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    • v.44 no.12
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    • pp.727-732
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    • 2007
  • In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

Review of interface engineering for high-performance all-solid-state batteries (계면 제어를 기반으로 한 고성능 전고체 전지 연구)

  • Insu, Hwang;Hyeon Jeong, Lee
    • Journal of Industrial Technology
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    • v.42 no.1
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    • pp.19-27
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    • 2022
  • This review will discuss the effort to understand the interfacial reactions at the anode and cathode sides of all-solid-state batteries. Antiperovskite solid electrolytes have received increasing attention due to their low melting points and anion tunability which allow controlling microstructure and crystallographic structures of this material system. Antiperovskite solid electrolytes pave the way for the understanding relationship between critical current density and mechanical properties of solid electrolytes. Microstructure engineering of cathode materials has been introduced to mitigate the volume change of cathode materials in solid-state batteries. The hollow microstructure coupled with a robust outer oxide layer effectively mitigates both volume change and stress level of cathode materials induced by lithium insertion and extraction, thus improving the structural stability of the cathode and outer oxide layer, which results in stable cycling performance of all-solid-state batteries.

Triallyl Borate as an Effective Separator/Cathode Interphase Modifier for Lithium-ion Batteries

  • Ha Neul Kim;Hye Rim Lee;Taeeun Yim
    • Journal of Electrochemical Science and Technology
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    • v.14 no.3
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    • pp.272-282
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    • 2023
  • Ni-rich layered oxides cathode has recently gained attention as an advanced cathode material due to their applicable energy density. However, as the Ni component in the layered site is increased, the high reactivity of Ni4+ results in parasitic reaction associated with decomposing electrolyte, which leads to a rapid decreasing the lifespan of the cell. The electrolyte additive triallyl borate (TAB) improves interfacial stability, leading to a stable cathode-electrolyte interphase (CEI) layer on the LNCM83 cathode. A multi-functionalized TAB additive can produce a uniformly distributed CEI layer via electrochemical oxidation, which implies an increase in long-term cycling performance. After 100 cycles at elevated temperature, the cell tested by 0.75 TAB retained 88.3% of its retention ratio, whereas the cell performed by TAB-free electrolyte retained 64.1% of its retention. Once the TAB additive formed CEI layers on the LNCM83 cathode, it inhibited the decomposition of carbonate-based solvents species in addition to the dissolution of transition metal components from the cathode. The addition of TAB to LNCM83 cathode material is believed to be a promising way to increase the electrochemical performance.

Fabrication and Cell Properties of Flattened Tube Segmented-in-Series Solid Oxide Fuel Cell-Stack Using Decalcomania Paper (전사지를 이용한 다전지식 평관형 고체산화물 연료전지 제작 및 셀 특성)

  • An, Yong-Tae;Ji, Mi-Jung;Park, Sun-Min;Shin, Sang-Ho;Hwang, Hae-Jin;Choi, Byung-Hyun
    • Korean Journal of Materials Research
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    • v.23 no.3
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    • pp.206-210
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    • 2013
  • In the segmented-in-series solid-oxide fuel cells (SIS-SOFCs), fabrication techniques which use decalcomania paper have many advantages, i.e., an increased active area of the electrode; better interfacial adhesion property between the anode, electrolyte and cathode; and improved layer thickness uniformity. In this work, a cell-stack was fabricated on porous ceramic flattened tube supports using decalcomania paper, which consists of an anode, electrolyte, and a cathode. The anode layer was $40{\mu}m$ thick, and was porous. The electrolyte layers exhibited a uniform thickness of about $20{\mu}m$ with a dense structure. Interfacial adhesion was improved due to the dense structure. The cathode layers was $30{\mu}m$ thick with porous structure, good adhesion to the electrolyte. The ohmic resistance levels at 800, 750 and $700^{\circ}C$ were measured, showing values of 1.49, 1.58 and $1.65{\Omega}{\cdot}cm^2$, respectively. The polarization resistances at 800, 750 and $700^{\circ}C$ were measured to be 1.63, 2.61 and $4.17cm^2$, respectively. These lower resistance values originated from the excellent interfacial adhesion between the anode, electrolyte and cathode. In a two-cell-stack SOFC, open-circuit voltages(OCVs) of 1.915, 1.942 and 1.957 V and maximum power densities(MPD) of 289.9, 276.1 and $220.4mW/cm^2$ were measured at 800, 750 and $700^{\circ}C$, respectively. The proposed fabrication technique using decalcomania paper was shown to be feasible for the easy fabrication of segmented-in-series flattened tube SOFCs.