• Title/Summary/Keyword: Single Spherical Particle

Search Result 6, Processing Time 0.07 seconds

Electrochemical Study of a Single Particle of Active Material for Secondary Battery using the Microelectrode (마이크로 전극에 의한 2차 전지용 활물질 단일 입자의 전기화학적 평가)

  • Kim Ho-Sung;Lee Choong-Gon
    • Journal of the Korean Electrochemical Society
    • /
    • v.9 no.2
    • /
    • pp.95-99
    • /
    • 2006
  • Electrochemical properties were studied for a single particle of active material of hydrogen storage alloy $(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$ and nickel hydroxides $(NiOH)_2$ for the secondary Nickel Metal Hydride (Ni-MH) batteries using the microelectrode, which was manipulated to make electrical contact with an active material particle for cyclic voltammograms (CV) and potential-step experiments. As a result of CV test, it was found that three kinds of hydrogen oxidation peaks at -0.9, -0.75 and -0.65 V and hydrogen evolution peak at -0.98 V for hydrogen storage alloy were separately observed and two kinds of peaks of proton oxidation/reduction at 0.45 and 0.32 V and oxygen evolution reaction (OER) at 0.6 V for nickel hydroxides were also more clearly observed. Furthermore hydrogen diffusion coefficient within a single particle was also found to vary the order between $10^{-9}\;and\;10^{-10}cm^2/s$ over the course of hydrogenation and dehydrogenation process for potential-step experiments.

Hydrogenation Study of Mg-based Alloys by mechanical Grinding Reaction for Hydrogen Storage of Fuel Cell (연료전지의 수소저장용 마그네슘계 합금의 기계적 분쇄 반응에 의한 수소화 특성 평가)

  • Kim, Ho-Sung;Suh, Hee-Seok;Cha, Jae-Sang
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.20 no.6
    • /
    • pp.69-74
    • /
    • 2006
  • The effects of mechanical grinding(MG) treatment on the hydrogen storage of $Mg_2Ni$ alloy and $Mg_2Ni$ composite alloy($Mg_2Ni+graphite$) were investigated by pressure-composition-temperature(PCT) measurement, the micro-electrode technique of electrochemistry and etc, in which PCT was measured at high temperature(around $300[^{\circ}C]$) of gas phase and a carbon-filament micro-electrode for electrochemical evaluation was manipulated to make electrical contact with the particle in 1M KOH aqueous solution. It was found that the hydrogenation properties of $Mg_2Ni$ and graphite composite particle were greatly improved by the mechanical grinding treatment by which the $Mg_2Ni$ and graphite composite alloys could be changed into microstructure and nano-level particles. namely; the hydrogen dissociation pressure of PCT measurement was decreased from 0.55[MPa] to 0.42[MPa] and hydrogenation peaks by micro-electrode were also observed more clearly on the same sample.

Electrochemical Study of Electrode Material of Ni-MH Battery for HEV and PEMFC Fuel Cell (HEV 및 PEMFC 연료전지용 니켈수소 전지의 전극재료에 대한 전기화학적 평가)

  • Kim, Ho-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.20 no.2
    • /
    • pp.24-28
    • /
    • 2006
  • Electrochemical hydrogenation/dehydrogenation properties were studied for a single particle of a Mm-based(Mm : misch metal) hydrogen storage alloy($MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3}$) for the anode of Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and the cyclic voltammetry and the galvanostatic charge/discharge experiments were performed. A single particle of the alloy showed the discharge capacity of 280[mAh/g], the value being 90[%] of the theoretical capacity. Data were compared with that of the composite film consisting of the alloy particles and a polymer binder, which is more practical form for Ni-MH batteries. Additionally, pulverization of the alloy particles are directly observed. Compared with the conventional composite film electrodes, the single particle measurements using the microelectrode gave more detailed, true information about the hydrogen storage alloy.

Kinetic Parameter Analysis of Hydrogen Diffusion Reaction for Hydrogen Storage Alloy of Fuel Cell System (연료전지의 수소저장용 합금에 대한 수소확산반응의 속도론적 해석)

  • Kim, Ho-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.20 no.2
    • /
    • pp.45-49
    • /
    • 2006
  • Electrochemical hydrogenation/dehydrogenation properties were studied for a single particle of a Mm-based(Mm : minh metal) hydrogen storage alloy($MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3}$) for fuel cell and Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and the potential-step experiment was carried out to determine the apparent chemical diffusion coefficient of hydrogen atom($D_{app}$) in the alloy. Since the alloy particle we used here was a dense, conductive sphere, the spherical diffusion model was employed for data analysis. $D_{app}$ was found to vary the order between $10^{-9}\;and\;10^{-10}[cm^2/s]$ over the course of hydrogenation and dehydrogenation process. Compared with the conventional composite film electrodes, the single particle measurements using the microelectrode gave more detailed, true information about the hydrogen storage alloy.

Electrochemical Hydrogenation Behavior of Surface-Treated Mg-based Alloys for Hydrogen Storage of Fuel Cell (연료전지의 수소저장용 마그네슘계 합금의 표면제어에 의한 전기화학적 수소화 거동 연구)

  • Kim, Ho-Sung;Lee, Jong-Ho;Boo, Seong-Jae
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.20 no.7
    • /
    • pp.46-52
    • /
    • 2006
  • The effects of surface treatment on the hydrogen storage properties of a $Mg_2Ni$ alloy particle were investigated by the microvoltammetric technique, in which a carbon-filament microelectrode was manipulated to make electrical contact with the particle in a KOH aqueous solution. It was found that the hydrogen storage properties of $Mg_2Ni$ at room temperature were improved by the surface treatment with a nickel plating solution. The sodium salts(sodium phosphate and sodium dihydrogen citrate) contained in the nickel plating solution made the alloy form an amorphous-like state, resulting in an improved hydrogen charge/discharge capacity at room temperature as high as about 150[mAh/g] from the original value of 17[mAh/g]. Potential-step experiment was carried out to determine the apparent chemical diffusion coefficient of hydrogen atom($D_{app}$) in the alloy. Since the alloy particle we used here was a dense, conductive sphere, the spherical diffusion model was employed for data analysis. $D_{app}$ was found to vary the order between $10^{-8}{\sim}10^{-9}[cm^2/s]$ over the course of hydrogenation and dehydrogenation process.

Electrochemical Behavior of a Nickel Hydroxide Particle for Ni-MH Battery by Microelectrode (마이크로전극에 의한 니켈수소전지용 수산화니켈 입자의 전기화학적 거동)

  • Kim, Ho-Sung;Oh, Ik-Hyun;Lee, Jong-Ho
    • Journal of the Korean Electrochemical Society
    • /
    • v.10 no.2
    • /
    • pp.145-149
    • /
    • 2007
  • Electrochemical studies were performed for a single particle of nickel hydroxide for the cathode of Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and electrochemical experiments were performed. As a result of cyclic voltammetry, the oxidation/reduction and oxygen evolution reaction (OER) are clearly separated for a single particle. The total cathodic charge (Qred) is practically constant for the scan rate investigated, indicating that the whole particle has reacted. The total anodic charge(Qox) was larger than that of reduction reaction, and the magnitude of oxygen evolution taking place as a side reaction was enhanced at lower scan rates. As a result of galvanostatic charge and discharge measurement, the discharge capacity of single particle was found to be 250 mAh/g, value being very close to the theoretical capacity (289 mAh/g). The apparent proton diffusion coefficient(Dapp) using potential step method inside the nickel hydroxide was found to range within $3{\sim}4{\times}10^{-9}\;cm^2/s$.