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- Elbouazzaoui, Kenza, et al.
(författare)
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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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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 399
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Hakim, Charifa, et al.
(författare)
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P-doped Hard Carbon as Anode Material for Sodium-ion Batteries
- 2019
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Ingår i: Proceedings of 2019 7th international renewable and sustainable energy conference (IRSEC). - : IEEE. - 9781728151526 ; , s. 754-756
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Konferensbidrag (refereegranskat)abstract
- The P-doped hard carbon was synthesized using carboxymethyl cellulose and phosphoric acid as the carbon and phosphorus precursors, respectively. The X-ray photoelectron spectroscopy (XPS) analysis reveals that the doped phosphorus atoms can incorporate into the carbon framework and most of them are connecting with carbon atoms to form P-C bonds. When used as anodes in sodium ion batteries, the obtained un-doped and P-doped hard carbon show poor electrochemical performances. The results indicate further optimization of the synthesis process is required. However, this approach opens up new possibilities to improve electrochemical performance of hard carbon anodes.
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| 3. |
- Hakim, Charifa, et al.
(författare)
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Understanding the redox process upon electrochemical cycling of the P2-Na0.78Co1/2Mn1/3Ni1/6O2 electrode material for sodium-ion batteries
- 2020
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Ingår i: Communications Chemistry. - : NATURE PUBLISHING GROUP. - 2399-3669. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The inclusion of nickel and manganese in layered sodium metal oxide cathodes for sodium ion batteries is known to improve stability, but the redox behaviour at high voltage is poorly understood. Here in situ X-ray spectroscopy studies show that the redox behaviour of oxygen anions can account for an increase in specific capacity at high voltages. Rechargeable sodium-ion batteries have recently attracted renewed interest as an alternative to Li-ion batteries for electric energy storage applications, because of the low cost and wide availability of sodium resources. Thus, the electrochemical energy storage community has been devoting increased attention to designing new cathode materials for sodium-ion batteries. Here we investigate P2- Na0.78Co1/2Mn1/3Ni1/6O2 as a cathode material for sodium ion batteries. The main focus is to understand the mechanism of the electrochemical performance of this material, especially differences observed in redox reactions at high potentials. Between 4.2 V and 4.5 V, the material delivers a reversible capacity which is studied in detail using advanced analytical techniques. In situ X-ray diffraction reveals the reversibility of the P2-type structure of the material. Combined soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering demonstrates that Na deintercalation at high voltages is charge compensated by formation of localized electron holes on oxygen atoms.
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