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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.

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.

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.

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