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Han M.H.,CICenergigune | Gonzalo E.,CICenergigune | Singh G.,CICenergigune | Rojo T.,CICenergigune | Rojo T.,University of the Basque Country
Energy and Environmental Science | Year: 2015

The room temperature Na-ion secondary battery has been under focus lately due to its feasibility to compete against the already well-established Li-ion secondary battery. Although there are many obstacles to overcome before the Na-ion battery becomes commercially available, recent research discoveries corroborate that some of the cathode materials for the Na-ion battery have indeed indisputable advantages over its Li-ion counterparts. In this publication, a comprehensive review of layered oxides (NaTMO2, TM = Ti, V, Cr, Mn, Fe, Co, Ni, and a mixture of 2 or 3 elements) as a viable Na-ion battery cathode is presented. Single TM systems are well characterized not only for their electrochemical performance but also for their structural transitions during the cycle. Binary TM systems are investigated in order to address issues regarding low reversible capacity, capacity retention, operating voltage, and structural stability. As a consequence, some materials already have reached an energy density of 520 mW h g-1, which is comparable to that of LiFePO4. Furthermore, some ternary TM systems retained more than 72% of their capacity along with over 99.7% Coulombic efficiency for 275 cycles. The goal of this review is to present the development of Na layered oxide materials in the past as well as the state of the art today in order to emphasize the compatibility and durability of layered oxides as powerful candidates for Na-ion battery cathode materials. © 2015 The Royal Society of Chemistry.

Piernas-Munoz M.J.,CICenergigune | Castillo-Martinez E.,CICenergigune | Bondarchuk O.,CICenergigune | Armand M.,CICenergigune | And 2 more authors.
Journal of Power Sources | Year: 2016

Cubic sodium Prussian White, Na2-xFe2(CN)6·yH2O, and potassium Prussian White, K2-xFe2(CN)6·yH2O, are prepared following a mild synthetic methodology. While cubic symmetry is confirmed by XRD and TEM, IR and XPS show characteristic features different from Prussian Blue compositions. When investigated as cathode materials in sodium ion batteries, both compounds exhibit reversible capacities above 140 mAh g-1 at 1C (ca. 80 mA g-1). While sodium Prussian White shows better high rate capability (10C/0.1C = 0.64), potassium Prussian White exhibits longer cycle stability, with up to 80% of capacity retention after 500 cycles. Interestingly, the potassium Prussian White phase also provides an increase of 0.35 V in the high voltage redox peak compared to the sodium Prussian White analogue ascribed to the preferential insertion of K+ ions instead of Na+, resulting in an increment of the gravimetric energy density. On the other hand, the insertion of Na+ seems to occur at the lower voltage plateau. This hybrid Na+ and K+ insertion in the framework of potassium Prussian White is most likely the responsible of the long cycle stability as a consequence of synergistic effects. © 2016 Elsevier B.V. All rights reserved.

Salado J.,University of the Basque Country | Insausti M.,University of the Basque Country | Lezama L.,University of the Basque Country | Gil De Muro I.,University of the Basque Country | And 2 more authors.
Chemistry of Materials | Year: 2011

One of the major challenges prior to a proper application of magnetic iron oxide nanocrystals is not only to understand the influence of the synthetic parameters on the final characteristics of the nanoparticles but also to optimize characterization methods in order to understand the magnetic behavior. First, a systematic study of the different parameters on a facile chemical synthetic route based on the thermal decomposition of iron(III) acetylacetonate, allowed a fine adjustment of the synthetic conditions to obtain oleic acid and oleylamine capped magnetite nanoparticles with perfectly defined size within 3.5-7 nm in diameter and organic content from 16.1 to 40.9%. Second, a complete characterization of samples by means of electron magnetic resonance (EMR) as a function of the angle and temperature was carried out. This technique allows to accurately elucidate the key characteristics of the deviation from the ideal superparamagnetic behavior observed in some samples by magnetic measurements. The optimization of the sample-handling for the EMR measurements emerged as a decisive step to provide reproducible results and to ultimately demonstrate that the lack of organic content adsorbed on the nanoparticle surface favored a ferromagnetic behavior. Furthermore, resonance lines ascribed to forbidden ΔM S= ± 2 transitions were observed in the EMR spectra of this system, which open up new research possibilities for evaluating interparticle interactions. © 2011 American Chemical Society.

Iturbe-Zabalo E.,Laue Langevin Institute | Iturbe-Zabalo E.,University of the Basque Country | Igartua J.M.,University of the Basque Country | Faik A.,CICEnergigune | And 3 more authors.
Journal of Solid State Chemistry | Year: 2013

Crystal structures of SrNdZnRuO6, SrNdCoRuO6, SrNdMgRuO6 and SrNdNiRuO6 double perovskites have been studied by X-ray, synchrotron radiation and neutron powder diffraction method, at different temperatures, and using the symmetry-mode analysis. All compounds adopt the monoclinic space group P21/n at room-temperature, and contain a completely ordered array of the tilted MO6 and RuO 6 octahedra, whereas Sr/Nd cations are completely disordered. The analysis of the structures in terms of symmetry-adapted modes of the parent phase allows the identification of the modes responsible for the phase-transition. The high-temperature study (300-1250 K) has shown that the compounds present a temperature induced structural phase-transition: P2 1/n→P42/n→Fm3̄m. © 2012 Elsevier Inc.

Gonzalo E.,CICenergigune | Han M.H.,CICenergigune | Lopez Del Amo J.M.,CICenergigune | Acebedo B.,CICenergigune | And 3 more authors.
Journal of Materials Chemistry A | Year: 2014

The solid state synthesis and electrochemical characterization of pure P2- and O3-Na2/3Fe2/3Mn1/3O2 have been carried out. Both phases have been characterized with XRD, solid state NMR, and ICP techniques. The initial charge capacity of the P2-phase reached 114.7 mA h g-1 and was followed by a discharge capacity of 151.09 mA h g-1 within the voltage range of 4.2-1.5 V at C/10. The capacity retention gradually decreased to 122.83 mA h g-1 at the 10th cycle, and then remained stable up to the 15th cycle. The O3-phase resulted in a first charge capacity of 134.01 mA h g-1 with a discharge capacity of 157.47 mA h g-1 under the same experimental conditions. The capacity retention gradually decreased to 122.24 mA h g-1 at the 10th cycle but, as in the other polymorph, the capacity remained stable at least up to the 15th cycle. Although the voltage profile is slightly different, the overall electrochemical performance of both phases is shown to be very similar, which implies that, contrary to common belief, the electrochemical performance of this compound does not highly depend on the layer stacking sequence adopted by the material. This journal is © the Partner Organisations 2014.

Sharma N.,University of New South Wales | Han M.H.,CICenergigune | Pramudita J.C.,University of New South Wales | Gonzalo E.,CICenergigune | And 3 more authors.
Journal of Materials Chemistry A | Year: 2015

Cathodes that feature a layered structure are attractive reversible sodium hosts for ambient temperature sodium-ion batteries which may meet the demands for large-scale energy storage devices. However, crystallographic data on these electrodes are limited to equilibrium or quasi-equilibrium information. Here we report the current-dependent structural evolution of the P2-Na2/3Fe2/3Mn1/3O2 electrode during charge/discharge at different current rates. The structural evolution is highly dependent on the current rate used, e.g., there is significant disorder in the layered structure near the charged state at slower rates and following the cessation of high-current rate cycling. At moderate and high rates this disordered structure does not appear. In addition, at the slower rates the disordered structure persists during subsequent discharge. In all rates examined, we show the presence of an additional two-phase region that has not been observed before, where both phases maintain P63/mmc symmetry but with varying sodium contents. Notably, most of the charge at each current rate is transferred via P2 (P63/mmc) phases with varying sodium contents. This illustrates that the high-rate performance of these electrodes is in part due to the preservation of the P2 structure and the disordered phases appear predominantly at lower rates. Such current-dependent structural information is critical to understand how electrodes function in batteries which can be used to develop optimised charge/discharge routines and better materials. © 2015 The Royal Society of Chemistry.

Han M.H.,CICenergigune | Gonzalo E.,CICenergigune | Casas-Cabanas M.,CICenergigune | Rojo T.,CICenergigune | Rojo T.,University of the Basque Country
Journal of Power Sources | Year: 2014

Electrochemistry and structural evolution of monoclinic NaNiO2 as a cathode material for Na-ion battery is reported. The initial charge capacity reached 160 mA h g-1 and the following discharge capacity of 114.6 mA h g-1, within the voltage range of 4.0-1.5 V at C/10. The multiple phase transition leading to O′3, P′3, P″3, O″3, and O*3 stacking types (NaNiO2, Na0.91NiO 2, Na0.84NiO2, Na0.81NiO2 and Na0.79NiO2 transitions, respectively, according to a previous report) during the 1st charge/discharge process is analysed using ex situ and in situ XRD techniques, and the stoichiometry of each phase is herein revised. The charge/discharge profile shows a highly reversible nature of the cathode, except that fully sodiated phase could not be achieved at the subsequent discharge. Two new phases have been discovered: a monoclinic O3 structure (designated as O 3) at the beginning of the charge (and end of discharge) and a P3 structure (designated as P*3) at 3.38 V that appeared only during the charge process. The composition of the new O 3-phase corresponds to Na0.83NiO2, which is the closest to the fully sodiated phase at room temperature achieved during the discharge process reported up to date, and the composition of the new Pá3-phase corresponds approximately to Na0.50NiO2. © 2014 Elsevier B.V. All rights reserved.

Orayech B.,University of the Basque Country | Urcelay-Olabarria I.,University of the Basque Country | Lopez G.A.,University of the Basque Country | Fabelo O.,Laue Langevin Institute | And 2 more authors.
Dalton Transactions | Year: 2015

A powdered La2CoMnO6 double perovskite was synthesized by the solid-state reaction method, and its crystal structure was investigated by (mode-crystallography) Rietveld analysis using X-ray and neutron powder diffraction data. La2CoMnO6 material is a monoclinic perovskite at room temperature, adopting the space group P21/n (a-a-b+), c ≈ 2ap and Z = 2. The P21/n phase can be described effectively by three distortion modes (GM4+, X3+, X5+) of the Fm3m (a0a0a0) parent phase. The comparative study of the material and those in the Ln2CoMnO6 and Ln2NiMnO6 families has shown a general trend in nearly all the materials, has served to select a common direction in the sub-space spanned by X5+, tri-linearly coupled to the order parameters of the cubic to monoclinic first order phase transition. This direction has been used to parametrize the refinements and to perform reliable refinements in the high-temperature intermediate distorted trigonal phase, R3 (a-a-a-), for which only one effectively acting irrep has been deduced: GM5+, physically a tilt of the oxygen sharing octahedra of Co and Mn. Its temperature evolution up to the prototype cubic phase has been fitted in the framework of the Landau Theory of Phase Transitions, showing a behavior typical of a tricritical point. The low-temperature neutron powder diffraction data have served to solve the magnetic structure: three indistinguishable ferromagnetic models with the space groups P21/n and P2′1/n′ are proposed. © The Royal Society of Chemistry 2015.

Orayech B.,University of the Basque Country | Ortega-San-Martin L.,Catholic University of Peru | Urcelay-Olabarria I.,University of the Basque Country | Lezama L.,BCMaterials | And 4 more authors.
Dalton Transactions | Year: 2015

The structural and magnetic properties of a series of ordered double perovskites with the formula Sr2Co1-xMgxTeO6 (x = 0.1, 0.2 and 0.5) are investigated by X-ray diffraction, low temperature neutron diffraction, electron paramagnetic resonance and magnetic susceptibility. The progressive substitution of the paramagnetic Co2+ high spin ion by the diamagnetic Mg2+, of about the same size, induces changes in the room temperature crystal structure, from a distorted P21/n phase for the undoped Sr2CoTeO6 oxide to the I4/m of the end member (Sr2MgTeO6). These perovskites experience structural transitions on heating, the temperature at which the transitions occur being smaller as x increases. The novel approach of mode-crystallography is used for the analysis. All oxides show antiferromagnetic exchange interactions between Co2+ ions but the long range antiferromagnetic order is not achieved for the phase with x = 0.5. The low temperature neutron diffraction data have been evaluated using a full symmetry analysis. Results are consistent with an unquenched orbital contribution of a high spin Co2+ ion. This journal is © The Royal Society of Chemistry.

Orayech B.,University of the Basque Country | Faik A.,CICenergigune | Lopez G.A.,University of the Basque Country | Fabelo O.,Laue Langevin Institute | Igartua J.M.,University of the Basque Country
Journal of Applied Crystallography | Year: 2015

Na0.5K0.5NbO3 has been synthesized by the conventional solid-state reaction process. The crystal structures and phase transitions, at low and high temperature, determined from the Rietveld refinements of X-ray and neutron powder diffraction data are reported. The structure evolution of Na0.5K0.5NbO3 in the temperature range from 2 to 875 14K shows the presence of three phase transitions. The first one, at ∼135 14 K, is discontinuous from the rhombohedral R3c (No. 161) space group to the room-temperature orthorhombic Amm2 (No. 38) space group; the second is discontinuous from the orthorhombic to the tetragonal P4mm space group (No. 99) at ∼46514 K, and the third is continuous from the tetragonal to the cubic space group (No. 221) at ∼70014 K. The obtained phase-transition sequence is R3c → Amm2 → P4mm → Pm m. No previous studies at low temperature have been carried out on the material with composition Na0.5K0.5NbO3. In the course of the determination of the three experimentally found phases, a novel method of refinement is presented. This is a step forward in the use of the symmetry-adapted modes as degrees of freedom in the refinement process: the parameterization of a direction in the internal space of the, in this case, sole irreducible representation, GM4 -, responsible for the symmetry breaking from the parent cubic space group to the polar distorted low-symmetry phases. Eventually, this procedure enables the calculation of the spontaneous polarization. © 2015 International Union of Crystallography.

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