Studies of Sn, Co, Al, and Fe additives in C14/C15 Laves alloys for NiMH battery application by orthogonal arrays

Ouchi²,

Nei³

et al. 2017

A combination of analytic tools and electrochemical testing was employed to study the contributions of Palladium (Pd) in a Zr-based AB 2 metal hydride alloy (Ti 12 Zr 22.8 V 10 Cr 7.5 Mn 8.1 Co 7 Ni 32.2 Al 0.4 ). Pd enters the A-site of both the C14 and C15 Laves phases and shrinks the unit cell volumes, which results in a decrease of both gaseous phase and electrochemical hydrogen storage capacities. On the other hand, the addition of Pd benefits both the bulk transport of hydrogen and the surface electrochemical reaction. Improvements in high-rate dischargeability and low-temperature performances are solely due to an increase in surface catalytic ability. Addition of Pd also decreases the surface reactive area, but such properties can be mediated through incorporation of additional modifications with rare earth elements. A review of Pd-addition to other hydrogen storage materials is also included.

Section: Pct Analysissupporting

confidence: 63%

Section: Methodsmentioning

confidence: 99%

Increase in the Surface Catalytic Ability by Addition of Palladium in C14 Metal Hydride Alloy

Ouchi²,

Nei³

et al. 2017

“…The slope factor (SF) indicates the degree of disorder (DOD) in an alloy. SF is defined as the ratio of the storage capacity between 0.01 MPa and 0.5 MPa to the total capacity in the desorption isotherm [2,19,51]. An alloy with a large SF has a flatter plateau and less DOD (less components or less variations among the components).…”

Section: Pressure-concentration-temperature Analysismentioning

confidence: 99%

Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys

Chang

Ouchi³

et al. 2016

Abstract:Mg, the A-site atom in C14 (MgZn 2 ), C15 (MgCu 2 ), and C36 (MgNi 2 ) Laves phase alloys, was added to the Zr-based AB 2 metal hydride (MH) alloy during induction melting. Due to the high melting temperature of the host alloy (>1500˝C) and high volatility of Mg in the melt, the Mg content of the final ingot is limited to 0.8 at%. A new Mg-rich cubic phase was found in the Mg-containing alloys with a small phase abundance, which contributes to a significant increase in hydrogen storage capacities, the degree of disorder (DOD) in the hydride, the high-rate dischargeability (HRD), and the charge-transfer resistances at both room temperature (RT) and´40˝C. This phase also facilitates the activation process in measurement of electrochemical discharge capacity. Moreover, through a correlation study, the Ni content was found to be detrimental to the storage capacities, while Ti content was found to be more influential in HRD and charge-transfer resistance in this group of AB 2 metal hydride (MH) alloys.

“…The system was charged at a current density of 50 mA·g −1 for 10 h and then discharged at a current density of 50 mA·g −1 until a cutoff voltage of 0.9 V was reached. Next, the system was discharged at a current density of 12 mA·g −1 until a cutoff voltage of 0.9 V was reached and again discharged at a current density of 4 mA·g −1 until a cutoff voltage at 0.9 V was reached [16,17]. AC impedance measurements were also performed to characterize the RT and low temperature (LT, −40 • C) electrochemical properties.…”

Section: Methodsmentioning

confidence: 99%

“…Slope factor (SF), defined as the ratio of desorption capacity between 0.01 and 0.5 MPa to total reversible capacity [6,17,22], is an indicator of the degree of disorder (DOD) in the MH alloy [38] and smaller in a more slanted isotherm. SF measured at 30 • C is listed in the fifth column in Table 4 and shows a decreasing trend with the increase in the boron content.…”

Section: Pct Analysismentioning

confidence: 99%

Effects of Boron-Incorporation in a V-Containing Zr-Based AB2 Metal Hydride Alloy

Chang

Ouchi³

et al. 2017

Abstract:In this study, boron, a metalloid element commonly used in semiconductor applications, was added in a V-containing Zr-based AB 2 metal hydride alloy. In general, as the boron content in the alloy increased, the high-rate dischargeability, surface exchange current, and double-layer capacitance first decreased and then increased whereas charge-transfer resistance and dot product of charge-transfer resistance and double-layer capacitance changed in the opposite direction. Electrochemical and gaseous phase characteristics of two boron-containing alloys, with the same boron content detected by the inductively coupled plasma optical emission spectrometer, showed significant variations in performances due to the difference in phase abundance of a newly formed tetragonal V 3 B 2 phase. This new phase contributes to the increases in electrochemical high-rate dischargeability, surface exchange current, charge-transfer resistances at room, and low temperatures. However, the V 3 B 2 phase does not contribute to the hydrogen storage capacities in either gaseous phase and electrochemical environment.