Yazar "Harfouche, Messaoud" seçeneğine göre listele

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    Copper-Induced Phase Transitions in NaMn1-xCuxO2: Structural Insights from Operando XAS, DFT Calculations, and Electrochemical Evaluation Using Laurus Nobilis-Derived Hard Carbon
    (Wiley-V C H Verlag Gmbh, 2026) Whba, Rawdah; Dogan, Ebru; Harfouche, Messaoud; Ozturk, Zeynep Reyhan; Farhan, Ahlam; Ipek, Semran; Corut, Sumeyye
    This study investigates the effect of Cu2+ doping on NaMn1- xCuxO2 layered cathodes. It also explores their integration with Laurus nobilis-derived hard carbon (HC) anodes for sodium-ion batteries (SIBs). Cu doping, particularly at x = 0.20, stabilizes the beta-NaMnO2 phase, suppresses Jahn-Teller distortions, and improves the structural stability of the MnO2 framework. In situ X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations confirm that Cu improved Na+ diffusion kinetics and reduces charge-transfer resistance, despite its electrochemical inactivity. X-ray Difraction (XRD), Raman, and Fourier transform infrared spectroscopy (FTIR) analyses reveal phase destabilization and segregation at higher Cu concentrations, while XPS indicates shifts in the Mn/Cu oxidation states, consistent with improved electronic conductivity and multivalent redox behavior. The scanning electron microscope (SEM and transmission electron microscopy (TEM) images demonstrate Cu-induced morphological transitions toward denser, more crystalline structures. Brunauer-Emmett-Teller (BET) measurements reveal that the L. nobilis-derived hard carbon (HC) anode possesses a high surface area and hierarchical porosity, which facilitated efficient Na + storage and rapid ion transport. Full-cell tests demonstrate high reversible capacity (approximate to 126 mAh g-1), excellent rate capability, and 56% capacity retention over 250 cycles. This work demonstrates that Cu doping and porous HC anodes synergistically enhance the structural and electrochemical performance of SIBs, thereby providing a sustainable strategy for advanced energy storage.
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    Cost-effective sodium-ion batteries using a Na0.67Mn0.9Ni0.1O2 cathode and lavender-flower-waste-derived hard carbon with a comparative presodiation approach
    (Elsevier, 2026) Dogan, Ebru; Moeez, Iqra; Whba, Rawdah; Ozcan, Sibel; Akkoc, Mitat; Altin, Emine; Harfouche, Messaoud
    The development of cost-effective, high-performance sodium-ion batteries (SIBs) is essential for large-scale energy storage systems. In this study, low-cost SIBs are fabricated using P2-type Na0.67Mn0.9Ni0.1O2 as the cathode and hard carbon (HC) derived from lavender flower waste as the anode. The synthesis of both electrode materials from widely accessible precursors ensures scalability and environmental sustainability. To address the sodium deficiency of HC, three different presodiation strategies-electrochemical, chemical, and direct contact-are systematically investigated, and the electrochemical performances of the full cells are compared. This evaluation reveals significant variations in the initial capacity, capacity retention, Coulombic efficiency, and rate performance. Although the direct-contact method delivers the highest initial capacity, electrochemical presodiation delivers superior long-term cycling stability and enhanced energy density. This comprehensive comparison of the electrochemical performance emphasizes the vital role of presodiation in enhancing the full-cell efficiency, while highlighting the potential methods for developing cost-effective and sustainable SIBs.
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    Influence of iron doping on α-NaMnO2 lattice symmetry: Insight from operando X-ray absorption, ex-situ structural analysis, and electrochemical performance using chestnut shell-derived hard carbon
    (Elsevier, 2026) Dogan, Ebru; Maiga, Abdulhadi; Whba, Rawdah; Harfouche, Messaoud; Ozturk, Zeynep Reyhan; Farhan, Ahlam; Altin, Emine
    The structural instability and moderate electrochemical performance of NaMnO2 cathodes limit the use of sodium-ion batteries (SIBs). This limitation is primarily due to lattice distortions and valence variations that occur during the cycling process. To address this limitation, NaMn(1-x)FexO(2) (0.00 <= x <= 0.50) powders were synthesized using a conventional solid-state method. Their structural and electrochemical properties were systematically investigated through a combination of structural characterization, in situ X-ray absorption spectroscopy, and computational modeling. X-ray diffraction and Rietveld refinement reveal a contraction of the beta-angle from 112 degrees to 105 degrees, indicative of a phase transition from alpha to alpha', with the x = 0.5 composition stabilizing as a single-phase alpha' structure. Fe incorporation reduces the average Mn valence from 3.23+ to 3.18+, thereby enhancing structural stability, as corroborated by electron diffraction and density functional theory (DFT) calculations. At the same time, hard carbon (HC) derived from chestnut shells was developed as a sustainable anode material, exhibiting a disordered framework favorable for Na+ storage. Electrochemical evaluation demonstrates that the x = 0.5 cathode delivers an initial half-cell capacity of 130.2 mAh/g, which declines to 77.1 mAh/g upon cycling. In contrast, the optimized electrode configuration affords improved stability. The HC anode attains a high reversible capacity of 317.3 mAh/g. Full-cell assemblies incorporating pre-sodiated HC anodes exhibit promising performance, underscoring the potential of this dual-material approach for developing high-performance, sustainable SIBs.
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    Interface-Engineered P2-Type Cathode and Biomass-Derived Anode for Stable Sodium-Ion Full Cells
    (Wiley-V C H Verlag Gmbh, 2025) Dogan, Ebru; Moeez, Iqra; Chung, Kyung Yoon; Whba, Rawdah; Altin, Emine; Harfouche, Messaoud; Karta, Mesut
    This work presents a sustainable and high-performance sodium-ion full-cell architecture by combining a core@shell Na0.67Mn0.5Fe0.5O2@Al2O3 cathode with a hard carbon anode derived from cherry seed biowaste. The P2-type cathode material is synthesized via a conventional solid-state method and coated with Al2O3 using a scalable wet-chemical route. Structural and surface analyses confirmed the formation of a uniform Al2O3 shell, which enhanced the cathode's electrochemical stability by mitigating Mn3(+)-induced distortion and suppressing electrolyte side reactions. In parallel, the hard carbon anode is produced from cherry seeds-a low-cost and abundant byproduct-through high-temperature pyrolysis, delivering high capacity and excellent cycling performance. Electrochemical evaluation of both electrodes in half-cell and full-cell configurations revealed favorable sodium-ion diffusion, robust structural integrity, and improved interfacial properties. The half-cell, assembled with Na0.67Mn0.5Fe0.5O2@Al2O3 cathode, demonstrated remarkable cycling stability and rate capability within a practical 1.5-3.5 V window, retaining 94.5% capacity after 100 cycles. In situ XRD studies further elucidated the phase transitions and stability of the cathode during cycling. This study demonstrates a sustainable and scalable pathway for sodium-ion battery development by integrating surface-engineered cathodes and biomass-derived anodes.
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    Investigation of Ti-substitution effects on structural and electrochemical properties of Na0.67Mn0.5Fe0.5O2batterycells
    (Wiley-Hindawi, 2020) Altin, Serdar; Altundag, Sebahat; Altin, Emine; Oz, Erdinc; Harfouche, Messaoud; Bayri, Ali
    Ti-substituted Na(0.67)Mn(0.5)Fe(0.5)O(2)powders were fabricated by quenching at high temperatures, and the structural properties were investigated by Fourier transform infrared (FTIR), Scanning Electron Microscope (SEM), X-ray powder diffraction (XRD), and X-ray absorption spectroscopy (XAS) measurements. According to XRD analysis, it was not observed any impurity phases and it was found that the lattice constants of the powders were slightly increased by Ti content. The change in the valence state of both Mn and Fe ions was investigated by X-ray absorption near edge structure (XANES), and it was found that Ti-substitution caused a decrease in the valance state of Fe in Na0.67Mn0.5Fe0.5O2. Fourier transform (FT) of XANES showed that the local structure around the metal ions changed with the addition of Ti ions. The cycling voltammetry (CV) graphs of Ti-substituted cells were almost the same as the pure sample, which may not change the cycling mechanism in the cells. According to galvanostatic cycling measurements at room temperature, the best performance was obtained with Ti-substitution of 0.06 to 0.09 in the structure. The effect of environmental temperature in the battery cells was investigated at 10 degrees C to 50 degrees C, and it was found that the battery performance depends on the environmental temperatures.
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    Magnetic Properties and Environmental Temperature Effects on Battery Performance of Na0.67Mn0.5Fe0.5O2
    (Wiley-V C H Verlag Gmbh, 2021) Altin, Serdar; Bayri, Ali; Altin, Emine; Oz, Erdinc; Yasar, Sedat; Altundag, Sebahat; Harfouche, Messaoud
    Herein, a modified solid state synthesis of Na0.67Mn0.5Fe0.5O2 and the results of a detailed investigation of the structural and magnetic properties via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis are reported. The magnetic properties of Na0.67Mn0.5Fe0.5O2 do not fit the Curie-Weiss law and a model regarding the spin configuration of the Mn and Fe ions and a possible ferrimagnetic order is suggested. Electrochemical measurements and ex situ structural analysis of the cathode material confirm the reversible structural transitions for the cells charged up to 4.0 V. Environmental temperature-dependent electrochemical measurements reveal a strong temperature dependence of both, the initial capacity and the capacity retention. Ex situ SEM, FTIR, and XRD studies on the battery membrane verify the formation of a Na2CO3 phase on the membrane, which blocks the Na ion diffusion through membrane pores and is responsible for the capacity fade for this compound.
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    Unveiling the outstanding full-cell performance of P2-type Na0.67(Mn0.44Ni0.06Fe0.43Ti0.07)O2 cathode active material for Na-ion batteries
    (Elsevier, 2024) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Harfouche, Messaoud; Oz, Erdinc; Avci, Sevda; Ji, Xiaobo
    In this study, we unravel the effect of Ni doping on the half-cell and full-cell performances of the Na0.67Mn0.5-xNixFe0.43Ti0.07O2 cathode materials where x varies between 0.02 and 0.1. The cyclic voltammetry (CV) analysis of the half-cells is performed at 10 degrees C, room temperature (RT), and 50 degrees C to elucidate the redox reaction mechanisms at different temperatures. Among the studied cathodes, the highest specific capacity is obtained fox = 0.06 which delivered a specific capacity of 186 mAh g-1 at C/3-rate. The full cell of Na0.67Mn0.44Ni0.06-Fe0.43Ti0.07O2/hard carbon couple is assembled in coin cell format and the specific capacity of the cell at C/2, 1C, and 2C rates are found as 153 mAh g- 1, 125 mAh g-1 and 120 mAh g-1, respectively. At the C/2-rate, the excellent capacity retention of the full cell is around 70% after 500 cycles delivering a specific capacity of 103 mAh g- 1. Along with the conventional physicochemical characterization methods such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman and Fourier-transform Infrared Spectroscopies (FTIR), we also utilize X-ray photoelectron spectroscopy (XPS) to bridge the nexus between the performance and the structure properties of the studied materials. Furthermore, we also employ synchrotron-based X-ray Absorption (XAS) to understand the local geometry of the optimized cathode materials in operando.