An investigation of the improvement in energy storage performance of Na 2/3 Mn 1/2 Fe 1/2 O 2 by systematic Al-substitut
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An investigation of the improvement in energy storage performance of Na2/3Mn1/2Fe1/2O2 by systematic Al-substitution S. Altin1 · S. Altundağ1 · E. Altin2 · M. Harfouche3 · A. Bayri1 Received: 28 May 2020 / Accepted: 18 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We successfully fabricated Na2/3Mn1/2Fe1/2−xAlxO2, where x = 0, 0.01, … 0.10, by a modified solid-state reaction technique. The structural properties of the Al-substituted samples were investigated by x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy and x-ray absorption fine structure (XAFS) measurements. It was found that there were no impurity phases in the XRD patterns of the samples and they fit the P63/mmc symmetry. The Al substitution in N a2/3Mn1/2Fe1/2O2 causes a decrease in the a-lattice parameter, but the c-parameter starts to increase after a certain substitution value of Al. We suggest that a certain proportion of Al in the samples triggers the change of the spin configuration of the Fe ions, and it may cause an increase in the lattice parameters. The size of the grains was found to be less than 0.9 µm, from SEM images for all samples. The valence states of the substituted samples as well as the local structure around Fe and Mn were investigated by means of XAFS measurements. The highest capacity for the first cycle was obtained as 134.3 mAh/g for x = 0.07, and the best capacity fade was found to be 0.23 for x = 0.08 substitution. So, the highest performance of the Al-substituted cells was found when 0.08 ≥ x ≥ 0.06. The environmental temperature effects on the battery cells were determined at 10 ºC, room temperature and 50 ºC, and it was found that the temperature plays a crucial role in the Na-ion batteries.
1 Introduction The modern technology of the portable battery has been developed with the necessary energy being provided by electrochemical energy storage cells. Li-ion battery systems have been widely used in everyday life, from smart watches to electrified vehicles. Because of this the increasing demand for lithium for battery fabrications and the decreasing lithium reservoirs in the world are causing research into new battery components to be necessary. When the periodic table is considered, it is seen that Li and Na ions have similar properties, and scientists have tried to develop new battery components including Na ions as replacements for Li ions including Na ions. The chemical
* S. Altin [email protected] 1
Physics Department, Inonu University, Malatya, Turkey
2
IBTAM, Inonu University, Malatya, Turkey
3
Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME), P.O. Box 7, 19252 Allan, Jordan
structures of Li-based electrode materials have been replicated as Na-based structures, and it is seen that they have electrochemical activities like those of Li-based structures. Among the Na-based cathode materials, the compounds which have Fe and Mn ions deserve attention due to their
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