| 1. |
- Bertrand, Philippe, et al.
(author)
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Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES
- 2017
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Conference paper (other academic/artistic)abstract
- In this presentation, we will present a recent example on electrode/electrolyte interfaces of materials for energy storage devices using hard X-rays photoelectron spectroscopy (HAXPES). A nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). [1] While electrode/electrolyte study has been performed widely on Li-ion battery, not so much attention as been addressed to the Na-ion technology so far. We will focus in this presentation to NaxCo2/3Mn2/9Ni1/9O2, a novel intercalation material that could be be used as cathode in Na-ion batteries. [2] During a typical charge/discharge cycle (i.e. extraction/insertion of Na+ ions), the oxidation state of the various transition metals in the compound changes in a reversible way. A step by step analysis of the first electrochemical cycle was carried out by HAXPES providing unique information on the oxidation state of Ni, Co and Mn as well as a very interesting insight into the passivation layer present at the surface of the electrode, which results from the degradation of the electrolyte components upon reaction. This investigation shows the role of the SPI and the complexity of the redox reactions. [3] [1] B. Philippe, M. Hahlin, K. Edström, T. Gustafsson, H. Siegbahn, H. Rensmo, J. Electrochem. Soc, 2016, 163, A178-A191[2] S. Doubaji, M. Valvo, I. Saadoune, M. Dahbi, K.Edström, J. Power Sources, 2014, 266, 275-281[3] S. Doubaji, B. Philippe, I. Saadoune, M. Gorgoi, T. Gustafsson, A. Solhy, M. Valvo, H. Rensmo, K. Edström, ChemSusChem, 2016, 9, 97-108
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| 2. |
- Dahbi, Mohammed, et al.
(author)
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A delithiated LiNi0.65Co0.25Mn0.10O2 electrode material : A structural, magnetic and electrochemical study
- 2009
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In: Electrochimica Acta. - : Elsevier Ltd. - 0013-4686 .- 1873-3859. ; 54:11, s. 3211-3217
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Journal article (peer-reviewed)abstract
- A crystalline LiNi0.65Co0.25Mn0.10O2 electrode material was synthesized by the combustion method at 900 °C for 1 h. Rietveld refinement shows less than 3% of Li/Ni disorder in the structure. Lithium extraction involves only the Ni2+/Ni4+ redox couple while Co3+ and Mn4+ remain electrochemically inactive. No structural transition was detected during cycling in the whole composition range 0 < x < 1.0. Furthermore, the hexagonal cell volume changes by only 3% when all lithium was removed indicating a good mechanical stability of the studied compound. LiNi0.65Co0.25Mn0.10O2 has a discharge capacity of 150 mAh/g in the voltage range 2.5–4.5 V, but the best electrochemical performance was obtained with an upper cut-off potential of 4.3 V. Magnetic measurements reveal competing antiferromagnetic and ferromagnetic interactions – varying in strength as a function of lithium content – yielding a low temperature magnetically frustrated state. The evolution of the magnetic properties with lithium content confirms the preferential oxidation of Ni ions compared to Co3+ and Mn4+ during the delithiation process.
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| 3. |
- Dahbi, Mohammed, et al.
(author)
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Effect of manganese on the structural and thermal stability of Li 0.3Ni0.7 - yCo0.3−yMn2yO2 electrode materials (y =0 and 0.05)
- 2011
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In: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 203:1, s. 37-41
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Journal article (peer-reviewed)abstract
- Thermal and structural stabilities of Li(0.3)Ni(0.7)Co(0.3)O(2) and Li(0.3)Ni(0.65)Co(0.25)Mn(0.10)O(2) chemically delithiated cathode materials were studied by X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry. The structure of the Li(0.3)Ni(0.7)Co(0.3)O(2) layered material (S.C. R-3 m) transforms first to the spinel-type structure (S.C. Fd3m) and then to the completely disordered Ni0-type structure (S.C. Fm3m). These structural transitions were accompanied by 10.2% oxygen loss and leads to an exothermic reaction, activated by the electrolyte, more energetic than that of Li(0.3)Ni(0.65)Mn(0.10)O(2) manganese substituted electrode. Furthermore, no structural changes were observed during the thermal treatment of Li(0.3)Ni(0.65)Co(0.25)Mn(0.10)O(2) and relatively lower oxygen loss was recorded. The obtained results prove the positive effect of manganese substitution on the electrochemical features of Li(0.3)Ni(0.7)Co(0.3)O(2).
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| 4. |
- Dahbi, Mohammed, et al.
(author)
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Electrochemical behavior of LiNi1-y-zCoyMnzO2 probed through structural and magnetic properties
- 2012
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 111:2, s. 023904-
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Journal article (peer-reviewed)abstract
- We have investigated LixNi1-y-zCoyMnzO2 compounds with y = 1/3, 0.25, 0.2, 0.1 and z = 1/3, 0.2, 0.1, 0.05 in order to study the influence of Ni and Mn concentration, cationic disorder, and crystallite size on the magnetic and charge/discharge behavior. The samples have been studied by means of x-ray diffraction, scanning electron microscopy, voltammetry, cycling capacity, and magnetometry. The discharge capacity increases with increasing Ni concentration as does the number of ferromagnetic interactions. With higher Mn concentration a higher capacity is observed together with formation of strong antiferromagnetic interactions driving the magnetic frustration to lower temperatures. Our results show that for sufficiently low Co concentrations a stable and magnetically more ordered structure can be obtained with excellent electrochemical properties, although a relatively large amount of Ni is present.
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| 5. |
- Difi, Siham, et al.
(author)
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Mechanisms and Performances of Na1.5Fe0.5Ti1.5(PO4)(3)/C Composite as Electrode Material for Na-Ion Batteries
- 2015
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:45, s. 25220-25234
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Journal article (peer-reviewed)abstract
- The properties, insertion mechanisms, and electrochemical performances of the Na1.5Fe0.5Ti1.5(PO4)(3)/C composite as electrode material for Na-ion batteries are reported. The composite was obtained by solid-state reaction and consists of porous secondary particles of submicron-sized particles coated by carbon. Detailed characterizations were performed by combining theoretical and experimental tools. This includes the determination of the crystal structure of Na1.5Fe0.5Ti1.5(PO4)(3) from both first-principles calculations and X-ray diffraction providing Na distribution over M1 and M2 interstitial sites, which is of importance for ionic conductivity. Na1.5Fe0.5Ti1.5(PO4)(3)/C was used as an electrode material at 2.2 V versus Na+/Na-0, exhibiting good Na-storage ability with a specific capacity of 125 mAh g(-1), close to the theoretical value, for the first discharge at C/10, good capacity retention, and Coulombic efficiency of 95% and 99.5% at the 60th cycle, respectively, and high power rate with a decrease of the specific capacity of only 14% from C/10 to 2C. These good performances have been related to the morphology of the composite and substitution of Fe for Ti, leading to an insertion mechanism that differs from that of NaTi2(PO4)(3). This mechanism was quantitatively analyzed from operand Fe-57 Mossbauer spectroscopy used for the first time in both galvanostatic and GITT modes.
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| 6. |
- Difi, Siham, et al.
(author)
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Role of iron in Na1.5Fe0.5Ti1.5(PO4)(3)/C as electrode material for Na-ion batteries studied by operando Mossbauer spectroscopy
- 2016
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In: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540.
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Conference paper (peer-reviewed)abstract
- The role of iron in Na1.5Fe0.5Ti1.5(PO4)(3)/C electrode material for Na batteries has been studied by Fe-57 Mossbauer spectroscopy in operando mode. The potential profile obtained in the galvanostatic regime shows three plateaus at different voltages due to different reaction mechanisms. Two of them, at 2.2 and 0.3 V vs Na+/Na-0, have been associated to redox processes involving iron and titanium in Na1.5Fe0.5Ti1.5(PO4)(3). The role of titanium was previously elucidated for NaTi2(PO4)(3) and the effect of the substitution of Fe for Ti was investigated with 57Fe Mossbauer spectroscopy. We show that iron is an electrochemically active center at 2.2 V with the reversible Fe3+/Fe2+ transformation and then remains at the oxidation state Fe2+ along the sodiation until the end of discharge at 0 V.
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| 7. |
- Doubaji, Siham, et al.
(author)
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On the P2-NaxCo1−y(Mn2/3Ni1/3)yO2 Cathode Materials for Sodium-Ion Batteries : Synthesis, Electrochemical Performance, and Redox Processes Occurring during the Electrochemical Cycling
- 2018
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:1, s. 488-501
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Journal article (peer-reviewed)abstract
- P2-type NaMO2sodiated layered oxides withmixed transition metals are receiving considerable attention foruse as cathodes in sodium-ion batteries. A study on solidsolution (1−y)P2-NaxCoO2−(y)P2-NaxMn2/3Ni1/3O2(y=0,1/3, 1/2, 2/3, 1) reveals that changing the composition of thetransition metals affects the resulting structure and the stabilityof pure P2 phases at various temperatures of calcination. For 0≤y≤1.0, the P2-NaxCo(1−y)Mn2y/3Niy/3O2solid-solutioncompounds deliver good electrochemical performance whencycled between 2.0 and 4.2 V versus Na+/Na with improved capacity stability in long-term cycling, especially for electrodematerials with lower Co content (y= 1/2 and 2/3), despite lower discharge capacities being observed. The (1/2)P2-NaxCoO2−(1/2)P2-NaxMn2/3Ni1/3O2composition delivers a discharge capacity of 101.04 mAh g−1with a capacity loss of only 3% after 100cycles and a Coulombic efficiency exceeding 99.2%. Cycling this material to a higher cutoffvoltage of 4.5 V versus Na+/Naincreases the specific discharge capacity to≈140 mAh g−1due to the appearance of a well-defined high-voltage plateau, but afteronly 20 cycles, capacity retention declines to 88% and Coulombic efficiency drops to around 97%. In situ X-ray absorption near-edge structure measurements conducted on composition NaxCo1/2Mn1/3Ni1/6O2(y= 1/2) in the two potential windows studiedhelp elucidate the operating potential of each transition metal redox couple. It also reveals that at the high-voltage plateau, all ofthe transition metals are stable, raising the suspicion of possible contribution of oxygen ions in the high-voltage plateau.
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| 8. |
- Doubaji, Siham, et al.
(author)
-
Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES
- 2016
-
In: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 9:1, s. 97-108
-
Journal article (peer-reviewed)abstract
- The cathode material P2-NaxCo2/3Mn2/9Ni1/9O2, which could be used in Na-ion batteries, was investigated through synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). This investigation clearly shows the role of the SPI and the complexity of the redox reactions. Cobalt, nickel, and manganese are all electrochemically active upon cycling between 4.5 and 2.0V; all are in the 4+ state at the end of charging. Reduction to Co3+, Ni3+, and Mn3+ occurs upon discharging and, at low potential, there is partial reversible reduction to Co2+ and Ni2+. A thin layer of Na2CO3 and NaF covers the pristine electrode and reversible dissolution/reformation of these compounds is observed during the first cycle. The salt degradation products in the SPI show a dependence on potential. Phosphates mainly form at the end of the charging cycle (4.5V), whereas fluorophosphates are produced at the end of discharging (2.0V).
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| 9. |
- Doubaji, Siham, et al.
(author)
-
Synthesis and characterization of a new layered cathode material for sodium ion batteries
- 2014
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 266, s. 275-281
-
Journal article (peer-reviewed)abstract
- Owing to the high abundance of sodium and its low cost compared to lithium, sodium ion batteries have recently attracted a renewed interest as possible candidates for stationary and mobile energy storage devices. Herein, we present a new sodium ion intercalation material, Na5CO2/3Mn2/9Ni1/9O2, which has been synthesized by a sol gel route in air followed by a heat treatment at 800 degrees C for 12 h. Its structure has been studied by X-ray diffraction showing that the material crystallized in a P2-type structure (space group P6(3)/mmc). As far as the electrochemical properties of NaxCo2/3Mn2/9Ni1/9O2 as positive electrode are concerned, this compound offers a specific capacity of 110 mAh g(-1) when cycled between 2.0 and 4.2 V vs. Na+/Na. The electrodes exhibited a good capacity retention and a coulombic efficiency exceeding 99.4%, as well as a reversible discharge capacity of 140 mAh g(-1) when cycled between 2.0 and 4.5 V. These results represent a further step towards the realization of efficient sodium ion batteries, especially considering that the synthesis method proposed here is simple and cost effective and that all the electrochemical measurements were carried out without any use of additives or any optimization for both the materials and the cell components.
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| 10. |
- Elbouazzaoui, Kenza, et al.
(author)
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NASICON-type Li0.5M0.5Ti1.5Fe0.5(PO4)3 (M = Mn, Co, Mg) phosphates as electrode materials for lithium-ion batteries
- 2021
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In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 399
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Journal article (peer-reviewed)abstract
- A correlation between the crystal structure, the ionic conductivity and the electrochemical performance in Lithium-ion batteries was established for a series of NASICON-type phosphates Li0.5M0.5Ti1.5Fe0.5(PO4)(3) (M = Mn, Co, Mg). These electrode materials, where the M1 site contains both lithium and the divalent cation M, were prepared using a simple sol-gel process while controlling the pH and the final synthesis temperature. The three phosphates crystallize in the rhombohedral system (S.G. R-3c) with comparable unit cell parameters but with slight difference in the local distortion of the PO4 tetrahedra as confirmed by the Raman study. The ionic conductivities of the Li0.5M0.5Ti1.5Fe0.5(PO4)(3) materials were measured at different temperatures using a wide range of frequencies. Mn-based phosphate shows the best features for application as electrode material for Li-ion batteries in term of the conductivity at room temperature and the activation energy of Li+ conduction process. The initial discharge capacity of 100 mAh.g(-1) was obtained for the Mg-based phosphate, 104.3 mAh.g(-1) for the Co-based material while the Mn-based material delivers the best first discharge capacity of 125.3 mAh.g(-1) with the lowest polarization in relation with its better conduction properties. This result was also confirmed by the rate capability tests where Mn-based phosphate shows enhanced electrochemical performance even at fast rate of 5C.
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