Yazar "Ates, Sule" seçeneğine göre listele

Listeleniyor 1 - 7 / 7
  • [ X ]
    Öğe
    Boron activity in the inactive Li2MnO3 cathode material
    (Elsevier, 2019) Ozkendir, O. Murat; Harfouche, Messaoud; Ulfat, Intikhab; Kaya, Cigdem; Celik, Gultekin; Ates, Sule; Aktas, Sevda
    Boron substituted Li2MnO3 cathode materials have frequently been studied and found to be inactive. In this reseach, crystal and electronic properties of the Li-ion cathode material with boron substitution having general formula; Li(2)Mn(1-x)BxO(3) (where x has values of 0.00, 0.05, 0.10, 0.15 and 0.20, respectively) were studied. The study revealed that, with the substitution of boron atoms in the manganese coordinates in the Li2MnO3 cathode materials, boron atoms acted as a landmark for the parent oxides by forming LiBO2 crystal domains. In the studied samples, boron atoms were determined as the key to construct new crystals and to restrict the excess of oxygen in the materials. Beyond the boron coordinations, the manganese atoms formed a cubic LiMn2O4 crystal structure which was reported to have good electrochemical properties. With the formation of the LiMn2O4 crystal, the substituted samples became a polycrystalline material with Li2MnO3- LiBO2- LiMn2O4 crystals. The obtained structure in the cathode materials have similarity with the general formula xLi(2)MnO(3)center dot(1-x)LiMn2O4 which had been reported to have good intercalation and electrochemical properties.
  • [ X ]
    Öğe
    Crystal and electronic structure study of the Li2Mn1-xNdxO3 battery cathode
    (Elsevier Science Inc, 2019) Celik, Gultekin; Aktas, Sevda; Ates, Sule; Ozkendir, O. Murat; Klysubun, Wantana
    Neodymium substituted Li2MnO3 samples were prepared by the solid-state reaction method. The crystal and electronic structure properties of the prepared samples were investigated by x-ray based techniques. According to the analysis, it was determined that Nd atoms did not sit in to the Cr coordinations in Nd substituted samples and built up a different crystal structure. To support the analysis of the crystal structure study of the samples, electronic structure properties of the Nd substituted samples were studied via the collected data by x-ray absorption fine structure (XAFS) spectroscopy from the Mn K-edge. The results of the data analysis revealed that due to the misfit with the ionic radii and also the oxidation states, substituted neodymium atoms built up isolated crystal domains in Li8Mn5Nd18O39 cubic crystal structure. The symmetry in Mn K-edge absorption data of the sample both in parent Li2MnO3 and Nd substituted samples confirmed that Mn coordinations has not been influenced by the Nd substitution.
  • [ X ]
    Öğe
    Electronic structure and electrochemical analysis of the Li2Mn1-xSexO3 materials
    (Elsevier, 2020) Ozkendir, O. Murat; Celik, Gultekin; Ates, Sule; Aktas, Sevda; Gunaydin, Selen; Harfouche, Messaoud; Bondino, Federica
    With the aim of probing the influence of the highly oxidizable selenium in the electrochemically inactive cathode Li2MnO3 material, samples were prepared with selenium substitution in the manganese coordination according to the general formula of Li2Mn1-xSexO3. In Li-ion batteries, oxygen instabilities are one of the major problems confronted that effect the performances of the cathode materials. The crystal and electronic structure properties of the materials were studied with x-ray absorption techniques. Selenium atoms were determined to build Li2SeO4 crystal and due to the oxygen removal during sample preparation mechanisms were determined to cause lower ionic conductivity than the parent Li2MnO3 oxide. The atomic distances in the materials were determined by the fits performed by the commercial code FEFF 8.2. Li2SeO4 crystal was determined as stacked between manganese and lithium atoms and isolated with each other.
  • [ X ]
    Öğe
    Structure and ionic conductivity of NASICON-type LATP solid electrolyte synthesized by the solid-state method
    (Elsevier Sci Ltd, 2024) Oksuzoglu, Fatih; Ates, Sule; Ozkendir, Osman Murat; Celik, Gultekin; Eker, Yasin Ramazan; Baveghar, Hadi
    The area of commercial battery innovation to replace safer batteries in widely used secondary batteries offers promising research into solid-state electrolytes (SSEs). Compared to lithium-ion electrolytes, solid-state electrolytes are inherently safer because they replace solvents with non-flammable materials. One of the promising materials for electrolytes today is based on inorganic materials, especially ceramics. Ceramics with superior mechanical, chemical and electrochemical stability and stability against high temperatures are of great interest. NASICON structured Li1.3 Al0.3 Ti1.7 (PO4)3 (LATP) is the most studied type of solid electrolyte due to its stability against air and humidity and high ionic conductivity. In this study, LATP samples were synthesized by solid-state synthesis method. The structural, morphological and charge transport properties (ionic conductivities) of the synthesized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Since the modifications applied during the sample preparation process can change the crystal structure and size of the target material, in this study, in order to minimize the formation of impurity phases and to achieve high ionic conductivity it was applied the different synthesis steps (temperature, time, grinding speed, etc.) from the literature. While the ionic conductivity value obtained is among the best values obtained by LATP synthesis methods in the literature, it is the best ionic conductivity value (1.3 x 10-3 S cm-1) obtained by the solid state synthesis method.
  • [ X ]
    Öğe
    Study of the local structure and electrical properties of gallium substituted LLZO electrolyte materials
    (Elsevier Science Sa, 2019) Aktas, Sevda; Ozkendir, Osman Murat; Eker, Yasin Ramazan; Ates, Sule; Atav, Ulfet; Celik, Gultekin; Klysubun, Wantana
    The solid-state lithium batteries are more stable than the batteries with liquid electrolyte, however their performance are also worse especially due to the low ionic conduction of their electrolyte. Garnet-type Li7La3Zr2O12 is a promising solid-state electrolyte candidate for lithium batteries. In this work the influence of gallium substitution on the electrical, crystal and electronic structure properties in the Li7La3Zr2O12 material were studied. Li7-3xGaxLa3Zr2O12 solid electrolytes were synthesized by solid state reaction method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), AC impedance spectroscopy and X-ray absorption spectroscopy (XAS) techniques. XRD and XAS analyses showed that the x = 0.05 sample is formed in the tetragonal phase with a space group of I4(1)/ acd:2 and the rest are formed in the cubic phase with a space group of I-43d due to strong coupling between outer shell electrons of the oxygen (O) and gallium (Ga) atoms. Electrochemical impedance spectroscopy (EIS) studies indicated that the tetragonal phase has the highest ionic conductivity, 3.04 x 10(-6) S cm(-1), among all other cubic phases. (C) 2019 Published by Elsevier B.V.
  • [ X ]
    Öğe
    The effect of Ti to the crystal structure of Li7-3xMxLa3Zr1.8Ti0.2O12 (M= Ga, In) garnet-type solid electrolytes as a second dopant
    (Sage Publications Inc, 2022) Saran, Sevda; Eker, Yasin Ramazan; Ates, Sule; Celik, Gultekin; Baveghar, Hadi; Ozkendir, Osman Murat; Atav, Ulfet
    Garnet-type solid-state electrolytes are promising candidates for solid-state lithium batteries, nevertheless their ionic conductivity is still not enough for commercial applications. On the other hand, doping still is the common way to improve the ionic conductivities of these solid electrolytes. In this study, mono and dual-doped garnet-type solid electrolytes were synthesised by substituting indium (In), gallium (Ga), indium-titanium (In-Ti) and gallium-titanium (Ga-Ti) to the Li7La3Zr2O12 structure by a solid-state reaction method. The contribution of substitutions to the formation of crystal phases was investigated by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). On the other hand, morphological analyses were done by scanning electron microscope (SEM) and the ionic conductivities of the solid electrolytes were determined by electrochemical impedance spectroscopy (EIS). The study showed that while Li7-3xInxLa3Zr2O12 (for x = 0.05, 0.10, 0.15, 0.20) and Li7-3xGaxLa3Zr2O12 (for x = 0.05) samples were formed in tetragonal phase with a space group of I41/acd:2, dual substituted Li7-3xInxLa3Zr1.8Ti0.2O12 and Li7-3xGaxLa3Zr1.8Ti0.2O12 solid electrolytes for all x values were formed in cubic phase with a space group of I-43d. The highest conductivity is reached for Li6.85Ga0.05La3Zr1.8Ti0.2O12. The radial distribution function studies showed that when more In and Ga atoms take place in the sites of Li atoms, more O atoms take place in the vicinity of both substituted In and Ga atoms within the Li7La3Zr1.8Ti0.2O12 (LLZTO) crystal framework which can eventuate in a change in the conduction mechanism.
  • [ X ]
    Öğe
    The Impact of Boron Compounds on the Structure and Ionic Conductivity of LATP Solid Electrolytes
    (Mdpi, 2024) Oksuzoglu, Fatih; Ates, Sule; Ozkendir, Osman Murat; Celik, Gueltekin; Eker, Yasin Ramazan; Baveghar, Hadi; Basyooni-M. Kabatas, Mohamed A.
    The increasing demand for safe and high-energy-density battery systems has led to intense research into solid electrolytes for rechargeable batteries. One of these solid electrolytes is the NASICON-type Li1+xAlxTi2-x(PO4)3 (LATP) material. In this study, different boron compounds (10% B2O3 doped, 10% H3BO3 doped, and 5% B2O3 + 5% H3BO3 doped) were doped at total 10 wt.% into the Ti4+ sites of an LATP solid electrolyte to investigate the structural properties and ionic conductivity of solid electrolytes using the solid-state synthesis method. Characterization of the synthesized samples was conducted using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The XRD patterns of the boron-doped LATP (LABTP) samples show that the samples have a rhombohedral phase with space group R3c together and low amounts of impurity phases. While all the LABTP samples exhibited similar ionic conductivity values of around 10-4 S cm-1, the LABTP2 sample doped with 10 wt.% H3BO3 demonstrated the highest ionic conductivity. These findings suggest that varying B3+ ion doping strategies in LATP can significantly advance the development of solid electrolytes for all-solid-state lithium-ion batteries.