| 1. |
- Biendicho, Jordi Jacas, et al.
(author)
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In situ investigation of commercial Ni(OH)(2) and LaNi5-based electrodes by neutron powder diffraction
- 2015
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In: Journal of Materials Research. - : Springer Science and Business Media LLC. - 0884-2914 .- 2044-5326. ; 30:3, s. 407-416
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Journal article (peer-reviewed)abstract
- Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available beta-Ni(OH)(2) and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the beta-Ni(OH)(2) electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to similar to 100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi(3.6)Al(0.4)Mn(0.3)Co(0.7), where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride gamma phase first and then to the beta phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.
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| 2. |
- Biendicho, Jordi Jacas, et al.
(author)
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New in-situ neutron diffraction cell for electrode materials
- 2014
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 248, s. 900-904
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Journal article (peer-reviewed)abstract
- A novel neutron diffraction cell has been constructed to allow in-situ studies of the structural changes in materials of relevance to battery applications during charge/discharge cycling. The new design is based on the coin cell geometry, but has larger dimensions compared to typical commercial batteries in order to maximize the amount of electrode material and thus, collect diffraction data of good statistical quality within the shortest possible time. An important aspect of the design is its modular nature, allowing flexibility in both the materials studied and the battery configuration. This paper reports electrochemical tests using a Nickel-metal-hydride battery (Ni-MH), which show that the cell is able to deliver 90% of its theoretical capacity when using deuterated components. Neutron diffraction studies performed on the Polaris diffractometer using nickel metal and a hydrogen-absorbing alloy (MH) clearly show observable changes in the neutron diffraction patterns as a function of the discharge state. Due to the high quality of the diffraction patterns collected in-situ (i.e. good peak-to-background ratio), phase analysis and peak indexing can be performed successfully using data collected in around 30 min. In addition to this, structural parameters for the beta-phase (charged) MH electrode obtained by Rietveld refinement are presented. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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| 3. |
- Biendicho, Jordi Jacas, et al.
(author)
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New Opportunities for Air Cathode Batteries; in-Situ Neutron Diffraction Measurements
- 2018
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In: Frontiers in energy research. - : Frontiers Media SA. - 2296-598X. ; 6
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Journal article (peer-reviewed)abstract
- Batteries with air electrodes are gaining interest as Energy Storage Systems (ESSs) for Electrical Vehicles (EVs) because of their high specific energy density. The electrochemical performance of these batteries is limited by the metallic electrode, which suffers structural transformations and corrosion during cycling that reduces the cycle life of the battery. In this context, relevant information on the discharge products may be obtained by in-situ neutron diffraction, a suitable technique to study electrodes that contain light elements or near neighbor elements in the periodic table. Case studies of MH-air and Fe-air batteries are highlighted.
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| 4. |
- Björling, Thomas, 1976-
(author)
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Synthesis and characterisation of Zintl hydrides
- 2008
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Doctoral thesis (other academic/artistic)abstract
- The synthesis, structural characterisation and the properties of the Zintl hydrides AeE2H2 and AeAlSiH (Ae = Ba, Ca, Sr; E = Al, Ga, In, Si, Zn) are reported. The first hydride in this class of compounds is SrAl2H2 which was discovered under an experiment by Gingl, who hydrogenated SrAl2 at various temperatures. (Gingl et al, Journal of Alloys and Compounds 306 (2000) 127-132). The intention was to form alanates, e.g. AlH4-, by terminating the three dimensional four connected aluminium network in SrAl2. The new hydride, SrAl2H2, has a partially conserved aluminium network. The three dimensional anionic network in SrAl2 is reduced to two dimensions in the hydride, with aluminium bonded to both aluminium and hydrogen. This type of bonding configuration has not been observed before.The hydrogenation of SrAl2 is straight forward, 190 oC and 50 bar, compared to the difficult synthesis of alanates and alane, AlH3. The latter synthesises uses aluminium in its zero oxidation state in contrast to the synthesis of SrAl2H2 from SrAl2. (In the SrAl2-precursor aluminium is reduced by the electropositive metal to -I.) Thus, the discovery shows a different route to alanates by using precursors with aluminium in a reduced state. If SrAl2H2 is further hydrogenated at 250 oC the two dimensional network breaks and Sr2AlH7 forms.We wanted to investigate if SrAl2H2 was a singularity or if other similar compounds exist. We wanted to study how hydrogenation of precursors similar to the aluminide result in 1) new routes to compounds with high hydrogen content, as alanates, 2) to investigate how the E-H bond is affected as function of the network composition among different ternary hydrides, in particular BaAlxSi2-xHx, and choice of active metal.BaGa2H2 and SrGa2H2, two hydrides isostructural with SrAl2H2, were synthesized from its precursors BaGa2 and SrGa2. In addition three ternary hydrides BaAlSiH, CaAlSiH and SrAlSiH were manufactured from their related AeAlSi precursors.All powders were characterized by neutron and x-ray diffraction methods.An increased stability towards water/moisture compared to ordinary saline hydrides was noticed, especially for the ternary hydrides. Heat stability was measured with DSC (differential scanning calorimetry). The hydrides BaGa2H2 and SrGa2H2 decompose around 300 oC at 1 atm. This is similar to isostructural SrAl2H2. The ternary hydrides BaAlSiH and SrAlSiH decompose at 600 oC, at 1 atm, which is the highest noticed temperature for compounds with Al-H bonds. Inelastic neutron scattering experiments showed that these hydrides Al-H and Sr-H bonds are really weak, even weaker then the Al-H interactions in alanates and alanes. These hydrides are probably stabilized be their lattices. The electric properties among the ternary hydrides were measured with IR-spectroscopy (diffuse reflectance). The ternary hydrides, AeAlSiH, are indirect semi conductors. BaGa2H2 and SrGa2H2 are conductors. The ternary hydrides, AeAlxSi2-xHx, may have adjustable band gaps, which we were not able to determine.This work is leading into a new research area within the field of metal hydrides.
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| 5. |
- Börjesson Axén, Jenny, 1986-, et al.
(author)
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A Structural Investigation into the OCV Hysteresis of the Ni(OH)2 Electrode
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Other publication (other academic/artistic)abstract
- Powder X-ray diffraction (XRPD), X-ray absorption spectroscopy (EXAFS and XANES) and Raman spectroscopy were used to study chemical changes in the polycrystalline nickel hydroxide positive electrode material of a NiMH battery at four states of charge: 0%, 50% and 100% charged, and 50% discharged. The two 50% samples were at the same state of charge but in different hysteresis states, manifested by differences in the open circuit potential. The nickel hydroxide electrodes consist of particles in the µm size range, and all measurements were performed ex situ. The material studied was taken from commercial batteries and as such contained both metallic nickel particles, cobalt, and zinc dopants in the active Ni(OH)2 material as well as a cobalt oxide surface layer. Combining the results from all the characterization methods was necessary to better understand the chemistry behind the physio-chemical hysteresis behavior in this complex system. Our results show that there are structural differences between the two 50% samples. Comparison of the XRPD results and the EXAFS results on the nickel edge indicate a presence of the kinetically favored TP2-NiOOH phase in the transition between β-Ni(OH)2 and β-NiOOH and that the amount differs between the two hysteresis states. The measurements on the zinc edge using EXAFS and XANES suggest short range differences in the active material bulk that stems from disorder. Raman spectroscopy measurements show a difference in degree of lithium intercalation in the LiCoO2 surface layer between the hysteresis states. As electrochemistry takes place on the surface of the particles, it is likely that differences in the surface structure are responsible for the open circuit voltage hysteresis. However, due to the coherence of the structure differences detected, it is probable that they are all connected and have a part in the observed behavior.
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| 6. |
- Chamoun, Mylad, et al.
(author)
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Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline Batteries
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Other publication (other academic/artistic)abstract
- Low cost rechargeable iron-air alkaline batteries have all essential attributes to adapt for large scale energy storage applications. To actualize this implementation needs to overcome the challenges including poor efficiency and short cycle lifetime. Herein, suitable synthesized catalysts for the air electrode were investigated prior to iron-air cell testing. NiCo2O4 as sole catalyst proved exceptional bifunctional OER/ORR activity and stability over 440 h operation in air. This catalyst fitted into an electrolyte and oxygen flow assisted rechargeable iron-air prototype and performed stable over 588 h and had an energy density of 377 Wh kg-1 Fe. Inadequate coulombic efficiencies of 75 – 85% and energy efficiencies around 50% hurt the performance of the cell though and needed further development. Nevertheless, the findings in this work reports the opportunities and obstacles of the rechargeable iron-air battery.
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| 7. |
- Chamoun, Mylad, et al.
(author)
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Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
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Other publication (other academic/artistic)abstract
- Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.
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| 8. |
- Chamoun, Mylad, et al.
(author)
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Rechargeability of aqueous sulfate Zn/MnO2 batteries enhanced by accessible Mn2+ ions
- 2018
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In: Energy Storage Materials. - : Elsevier BV. - 2405-8289 .- 2405-8297. ; 15, s. 351-360
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Journal article (peer-reviewed)abstract
- The Zn/MnO2 battery is safe, low cost and comes with a high energy density comparable to Li-ion batteries. However, irreversible spinel phases formed at the MnO2 electrode limits its cyclability. A viable solution to overcome this inactive phase is to use an aqueous ZnSO4-based electrolyte, where pH is mildly acidic leading to a different reaction mechanism. Most importantly, the addition of MnSO4 achieves excellent cyclability. How accessible Mn2+ ions in the electrolyte enhances the reversibility is presented. With added Mn2+, the capacity retention is significantly improved over 100 cycles. Zn2+ insertion plays an important role on the reversibility and a hydrated layered Zn-buserite structure formed during charge is reported. Furthermore, Zn4SO4(OH)(6) center dot 5H(2)O precipitates during discharge but is not involved in the electrochemical reaction. This precipitate both buffers the pH and partly insulates the surface. Described in operando study show how the phase transformations and the failure mechanisms depend on the presence of Mn2+-ions in the electrolyte. These results give insight necessary to improve this battery further to make it a worthy contender to the Li-ion battery in large scale energy storage solutions.
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| 9. |
- Chamoun, Mylad, 1989-
(author)
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Rechargeable Aqueous Batteries Based on Available Resources : Investigation and Development towards Efficient Battery Performance
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Batteries employing water based electrolytes enable extremely low manufacturing costs and are inherently safer than Li-ion batteries. Batteries based on zinc, manganese dioxide, iron, and air have high energy relevancy, are not resource restricted, and can contribute to large scale energy storage solutions. Zinc has a rich history as electrode material for primary alkaline Zn–MnO2 batteries. Historically, its use in secondary batteries has been limited because of morphological uncertainties and passivation effects that may lead to cell failure. Manganese dioxide electrodes are ineffective as rechargeable electrodes because of failure mechanisms associated with phase transformations during cycling. The irreversibility of manganese dioxide is strongly correlated to the formation of the electrochemically inactive spinel, Mn3O4/ZnMn2O4. The development of the iron electrode for Fe–air batteries was initiated in late the 1960s and these batteries still suffer from charging inefficiency, due to the unwanted hydrogen evolution reaction. Meanwhile, the air electrode is limited in long-term operation because of the sluggish oxygen evolution and reduction kinetics. These limitations of the Fe–air battery yield poor overall efficiencies, which bring vast energy losses upon cycling.Herein, the limitations described above were countered for rechargeable Zn–MnO2 and Fe–air batteries by synthesizing electrode materials and modifying electrolyte compositions. The electrolyte mixture of 1 M KOH + 3 M LiOH for rechargeable alkaline Zn–MnO2 batteries limited the formation of the inactive spinels and improved their cycle life significantly. Further, the formation of the inactive spinels was overcome in mildly acidic electrolytes containing 2 M ZnSO4, enabling the cells to cycle reversibly at lower pH via a distinctive reaction mechanism. The iron electrodes were improved with the addition of stannate, which suppressed hydrogen evolution. Furthermore, optimal charge protocols of the iron electrodes were identified to minimize the hydrogen evolution rate. On the air electrode, the synthesized NiCo2O4 showed excellent bifunctional catalytic activity for oxygen evolution and reduction, and was incorporated to a flow assisted rechargeable Fe–air battery, in order to prove the practicability of this technology. Studies of the electrode materials on the micro, macro, nano, and atomic scales were carried out to increase the understanding of the nature of and interactions between of these materials. This included both in operando and ex situ characterization. X-ray and neutron radiation, and analytical- and electrochemical methods provided insight to improve the performance and cycle life of the batteries.
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| 10. |
- Chamoun, Mylad, et al.
(author)
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Stannate Increases Hydrogen Evolution Overpotential on Rechargeable Alkaline Iron Electrodes
- 2017
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:6, s. A1251-A1257
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Journal article (peer-reviewed)abstract
- Alkaline iron electrodes present some challenges for use in secondary batteries that are associated with low coulombic efficiency and discharge utilization. Low coulombic efficiency is correlated to the hydrogen evolution reaction that takes place during charge. In this work, we demonstrate rechargeable alkaline iron electrodes with significant capacity retention over 150 cycles with high efficiency by suppressing the hydrogen evolution with stannate. Adding stannate to the alkaline electrolyte when cycling the iron electrode drastically changes the electrochemistry. The additive brings on two advantageous attributes for the iron electrode: increased hydrogen evolution overpotential, and a flat and prolonged discharge curve at typical battery operation. These attributes were provided by a novel intermediate phase that was detected from in situ neutron diffraction measurements. This phase was only detected in situ while it decomposed ex situ, and indicated a solid solution constituted by some of the elements present in the electrode.
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