Stoichiometry in Inter-Metallic Compounds for Hydrogen Storage Applications

Young, K.

doi:10.5772/35397

Cited by 10 publications

(12 citation statements)

References 19 publications

(18 reference statements)

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“…In addition, the B/A ratios in the C14 phase are higher than those in the C15 phases. The initial increase followed by a decrease in the C14 lattice parameters found through XRD analysis can be explained by the balance between the decrease in the content of relatively small Ti (larger C14 unit cell) and the increase in B/A ratio (smaller C14 unit cell [61]). The B/A ratio in the TiNi phase is calculated based on the assumption of V occupying the A-site [27] and the results are still higher than 1, which indicates the possibility of other Zr x Ni y secondary phases with higher B/A ratios.…”

Section: X-ray Diffractometer Analysismentioning

confidence: 96%

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

Chang

Kim

Ouchi³

et al. 2016

Batteries

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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.

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Section: X-ray Diffractometer Analysismentioning

confidence: 96%

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

Chang

Kim

Ouchi³

et al. 2016

Batteries

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“…For MH alloys that are sensitive to oxygen contamination from the reduction of ceramic refractory used as furnace crucible, a skull VIM melting can be used (Figure 8). MA in a shaker mill or an attritor is a popular method for making meta-stable/amorphous alloys not allowed in the phase diagram [45] (Figure 9). …”

Section: Melting and Castingmentioning

confidence: 99%

“…An IMC with a fixed stoichiometry comes with a large negative heat formation [45]. The different energy levels of anti-site and vacancy defects in a specific IMC may change its stoichiometry range [251][252][253].…”

Section: Stoichiometrymentioning

confidence: 99%

“…The reason that more hypo-stoichiometric IMCs tend to form as the radii ratio increases is that a relatively small B-atom more rapidly forms a double B in A-site (dumbbell model [254]) and further increases the B/A ratio. The characteristics of a few off-stoichiometric C14 MH alloys were previously compared [45,255,256] and important results are summarized in the next three sections. Table 9.…”

Section: Stoichiometrymentioning

confidence: 99%

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C14 Laves Phase Metal Hydride Alloys for Ni/MH Batteries Applications

2017

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C14 Laves phase alloys play a significant role in improving the performance of nickel/metal hydride batteries, which currently dominate the 1.2 V consumer-type rechargeable battery market and those for hybrid electric vehicles. In the current study, the properties of C14 Laves phase based metal hydride alloys are reviewed in relation to their electrochemical applications. Various preparation methods and failure mechanisms of the C14 Laves phase based metal hydride alloys, and the influence of all elements on the electrochemical performance, are discussed. The contributions of some commonly used constituting elements are compared to performance requirements. The importance of stoichiometry and its impact on electrochemical properties is also included. At the end, a discussion section addresses historical hurdles, previous trials, and future directions for implementing C14 Laves phase based metal hydride alloys in commercial nickel/metal hydride batteries.

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“…Except for the peaks marked as "A", there are some strong peaks related to metallic Mn and Co (marked as "1" and "2" in Figure XRD patterns before and after electrochemical cycling are shown in Figure 5. As our previous study has shown [62], the two broad peaks at approximately 23° and 42° (marked as "A") are from the broadening of the MgNi2 and Mg2Ni phases. These two broad peaks exist in all of the cycled AR3 samples, suggesting high stability for MgNi2 and Mg2Ni during cycling.…”

Section: Effects Of Cs 2 Co 3 Addition On Mgni Alloymentioning

confidence: 99%

Effects of Cs2CO3 Additive in KOH Electrolyte Used in Ni/MH Batteries

Yan

Nei²,

et al. 2017

Batteries

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Abstract:The effects of Cs 2 CO 3 addition in a KOH-based electrolyte were investigated for applications in nickel/metal hydride batteries. Both MgNi-based and Laves phase-related body-centered cubic solid solution metal hydride alloys were tested as the anode active materials, and sintered β-Ni(OH) 2 was used as the cathode active material. Certain amounts of Cs 2 CO 3 additive in the KOH-based electrolyte improved the electrochemical performances compared with a conventional pure KOH electrolyte. For example, with Laves phase-related body-centered cubic alloys, the addition of Cs 2 CO 3 to the electrolyte improved cycle stability (for all three alloys) and discharge capacity (for the Al-containing alloys); moreover, in the 0.33 M Cs 2 CO 3 + 6.44 M KOH electrolyte, the discharge capacity of Mg 52 Ni 39 Co 3 Mn 6 increased to 132%, degradation decreased to 87%, and high-rate dischargeability stayed the same compared with the conventional 6.77 M KOH electrolyte. The effects of Cs 2 CO 3 on the physical and chemical properties of Mg 52 Ni 39 Co 3 Mn 6 were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, inductively coupled plasma, and electrochemical impedance spectroscopy. The results from these analyses concluded that Cs 2 CO 3 addition changed both the alloy surface and bulk composition. A fluffy layer containing carbon was found covering the metal particle surface after cycling in the Cs 2 CO 3 -containing electrolyte, and was considered to be the main cause of the reduction in capacity degradation during cycling. Also, the Cs 2 CO 3 additive promoted the formations of the C-O and C=O bonds on the alloy surface. The C-O and C=O bonds were believed to be active sites for proton transfer during the electrochemical process, with the C-O bond being the more effective of the two. Both bonds contributed to a higher surface catalytic ability. The addition of 0.33 M Cs 2 CO 3 was deemed optimal in this study.

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Stoichiometry in Inter-Metallic Compounds for Hydrogen Storage Applications

Cited by 10 publications

References 19 publications

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

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

C14 Laves Phase Metal Hydride Alloys for Ni/MH Batteries Applications

Effects of Cs2CO3 Additive in KOH Electrolyte Used in Ni/MH Batteries

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