Yazar "Ji, Xiaobo" seçeneğine göre listele

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    High-performance P2-Na0.67Mn0.85Cu0.15O2/Hard carbon full cell Na-ion battery: Pre-Sodiation of anode, p/n ratio optimizations, and Operando XAS studies
    (Pergamon-Elsevier Science Ltd, 2023) Altundag, Sebahat; Altin, Emine; Altin, Serdar; Ates, Mehmet Nurullah; Ji, Xiaobo; Sahinbay, Sevda
    Na-ion batteries have gained significant attention as a cost-effective and efficient energy storage option for large scale applications, serving as an alternative to the Li-ion batteries. However, commercialization of these batteries is still many steps away since most cathode materials suffer from significant capacity loss and more full-cell studies are required. In this work, we report the electrochemical properties of half-and full-cells of P2-type Na0.67Mn0.85Cu0.15O2 synthesized by solid state technique. X-ray diffraction, FT-IR, and Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques are used to determine the structural properties. Surface properties are studied by X-ray photoelectron spectroscopy and Bru-nauer-Emmett-Teller techniques. Half cells and full cells were constructed with Na-metal and hard carbon, respectively. Na-ion diffusion kinetics at 10 degrees C, room temperature, and 50 degrees C were determined experimentally. Galvanostatic cycling tests on half-cells show capacity values of 165/124 mAh/g for the 1./100. cycles with 24.8 % capacity fade. Operando x-ray absorption spectroscopy measurements were utilized to study local structural modification around transition metal ions during charge/discharge. In the full-cell studies, electrode mass ratio (p/n) and parameters for presodiation of hard carbon were optimized. Using 30 mA/g current density, the un-processed and the pre-sodiated full-cells reach capacity values of 48 mAh/g (p/n = 2.5) and 150 mAh/g (p/n = 0.75 and 1.15), respectively.
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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.
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    ZIF-12-derived N-doped Fe/Co/S/@C nanoparticles as high-performance composite anode electrode materials for lithium-ion batteries
    (Elsevier Science Sa, 2022) Bugday, Nesrin; Ates, Mehmet Nurullah; Duygulu, Ozgur; Deng, Wentao; Ji, Xiaobo; Altin, Serdar; Yasar, Sedat
    Different sulfide species of both iron and cobalt metals (FeS2, FeS, CoS, and FeCoS2) are composed together in N-doped porous carbon (NPC) for the synthesis of composite anode materials (labeled as Fe/Co/S@NPC-T hereafter, T = 700, 800, 900) by sulfurization and pyrolysis of Fe/Co-based zeolitic imidazolate framework (ZIF-12). Their structural properties are investigated by XRD, FTIR, SEM, TEM, BET and XPS analysis, and Fe/ Co/S@NPC-T composite materials, heat treated at different temperatures, are used as anode materials in rechargeable lithium-ion batteries. According to XRD results, the heat treatment of the Fe/Co@ZIF-12/S heat treated at 900 ? leads to the formation of the FeCoS2 phase (66 %) along with CoS (33 %) phase impurity. The heat treatment of the Fe/Co@ZIF-12/S heat treated at 800 ? causes the formation of the main phase of FeCoS2 with minor impurity phases of CoS and FeS2. However, pyrolysis of the Fe/Co@ZIF-12/S heat treated at 700 & DEG;C leads to the formation of the FeCoS2, CoS, FeS, and FeS2 phases. Among the samples, the highest BET surface area is 53.4 m2/g for the Fe/Co/S@NPC-90 0 sample. The CV analysis of the battery cell shows anodic and cathodic redox peaks, which belong to the redox reaction of CoS, FeS2, and FeS. The first dis-charge capacities of the cells for Fe/Co/S@NPC-70 0, Fe/Co/S@NPC-80 0 and Fe/Co/S@NPC-90 0 are 395, 963, 574 mA h/g at 300 mA/g, and 229, 835 and 1024 mA h/g at 1000 mA/g, respectively. (c) 2022 Elsevier B.V. All rights reserved.