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    High-performance Na-ion full-cells with P2-type Na0.67Mn0.5-xNixFe0.43Al0.07O2 cathodes: Cost analysis for stationary battery storage systems
    (Elsevier, 2024) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Bulut, Fatih; Oz, Erdinc; Sahinbay, Sevda; Altin, Serdar
    Na -ion batteries are viable alternatives to Li-ion batteries especially for stationary applications. Developing suitable electrode materials, half-cell and full-cell studies and cost analysis are major steps and challenges for their commercialization. In this study, we report the synthesis of a promising cathode material, Na0.67Mn0.5- xNixFe0.43Al0.07O2 (x = 0.02-0.10 with Delta x = 0.02), using a modified solid-state synthesis technique. The materials were heated at high temperature for 6 h in air and quenched in liquid N-2. We determined the solubility limit of Ni in Na0.67Mn0.5Fe0.43Al0.07O2 as x <= 0.06. The interlayer separation increases with increasing Ni content due to the ionic radii difference between Mn and Ni. X-ray photoelectron spectroscopy (XPS) measurements evidence the valance state of Ni in the x = 0.06 sample as 2+ and 3+. Cyclic voltammetry (CV) analysis of the half-cells were performed at 10 C-degrees, room temperature, and 50 degrees C to observe the effect of environmental temperature on redox mechanism. The highest half-cell capacity of the cells was determined as 181 mAh/g for x = 0.06 at C/3-rate. Artificial solid electrolyte interface (SEI) formation was performed on the hard carbon anode by presodiation technique and the full-cells of Na0.67Mn0.44Ni0.06- Fe0.43Al0.07O2/hard carbon were assembled in CR2032 coin cells. The capacity values of the cells at C/2, C, and 2C-rate were determined as 131.4 mAh/g, 116 mAh/g and 100.8 mAh/g for the 1 cycle and 33 mAh/g, 40.6 mAh/g and 49.9 mAh/g for the 500th cycle, respectively. The cost analysis for the commercial package for stationary energy storage system was performed by BatPac program and results are discussed.
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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.