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Öğe Boron-doped porous carbon material derived from ZIF-11: Investigation of cotton fabric supercapacitor and Li-ion battery performances(Wiley, 2022) Bugday, Nesrin; Altin, Serdar; Bulut, Fatih; Altin, Emine; Yasar, SedatNitrogen-doped porous carbon (NPC@ZIF-11) and boron-NPC (BNPC@ZIF-11) materials were synthesized by pyrolysis methods, and structural characterization of the compounds was carried out by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Brunauer-Elmet-Teller technique, Raman spectroscopy, and inductively coupled plasma-mass spectrometry techniques. The ZIF-11 was converted to the NPC@ZIF11 by pyrolysis. BNPC@ZIF-11 was fabricated from NPC@ZIF-11 by pyrolysis in the presence of phenylboronic acid. The fabric supercapacitor, sandwich-type supercapacitor, and Li-ion battery performances of NPC@ZIF-11 and BNPC@ZIF-11 were investigated. The capacity of the Li-ion cell was found as 720 mAh g(-1) for the first cycle, and it was decreased to 250 mAh g(-1) after 100 cycles. The capacitance values of the cylindrical devices were 92 F g(-1) and 115.6 F g(-1), for C1 and C4000 in KOH electrolytes. The BNPC@ZIF-11 was used as an electrode material on cotton fabric, and the highest obtained capacitance was 72.8 mF for 0.1 mA, which is a promising result for wearable energy storage materials.Öğe High-Performance Ag-Doped Na0.67MnO2 Cathode: Operando XRD Study and Full-Cell Performance Analysis with Presodiated Anode(Amer Chemical Soc, 2023) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Altin, Emine; Moeez, Iqra; Chung, Kyung Yoon; Arshad, MuhammadThe key challenges of Na-ion batteries are to design structurally stable electrodes and reach high-enough capacities with full-cells. In this study, we report the positive effects of Ag substitution/addition to Na0.67MnO2. We determined that some of the intended Ag was incorporated into the structure, while the rest remained in metallic form. Ag substitution/addition increases the capacity (208 mA h/g at C/3 rate) and improves the cycle life of Na0.67MnO2 (42% capacity fade with 100 cycles) in half-cells. We attribute these results to an enlarged interlayer spacing due to the large ionic radius of Ag, a suppressed Jahn-Teller effect due to the reduced number of Mn3+ ions, and an increased electrical conductivity due to the presence of metallic Ag. We also produced full-cells with an electrochemically presodiated hard carbon anode. We reached a very high initial capacity of 190 mA h/g at the C/3 rate, showing that Ag substituted/added Na0.67MnO2 is a promising candidate for commercialization of Na-ion batteries.Öğe High-performance electrodes for Li-ion cell: Heteroatom-doped porous carbon/CoS structure and investigation of their structural and electrochemical properties(Wiley, 2022) Bugday, Nesrin; Altin, Emine; Altin, Serdar; Yasar, SedatAs an essential class of anode materials, the synthesis and characterization of CoS@ZIF-12-C composite anode materials are reported. The two-step synthesis of CoS nanoparticles embedded in N-doped porous carbon by using a metal-organic framework (MOF) as the template. After structural characterization of CoS@ZIF-12-C composite materials, the main phase was found as CoS with symmetry of P63mmc. Benefiting from the CoS embedded in porous carbon structure, the half Li-ion battery cell tests of CoS@ZIF-12-C composite materials were performed by a 2-electrode method using CR2032 cells, and the capacities of the cells were measured for 200 cycles using 300 mAg(-1) and 500 cycles using 1000 mAg(-1). The first discharge capacities of the cells for 1000 mAg(-1) were found as 458, 1178, and 815 mAhg(-1) for CoS@ZIF-12-C-T, T = 700, 800, and 900 degrees C, respectively. An unexpected capacity increase was observed for the CoS@ZIF-12-C-700 and CoS@ZIF-12-C-900 half cells during the cycling. Ex-situ x-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and cyclic voltammetry (CV) analysis were performed after cycling of the cells for explanations of the capacity increase. Ex-situ XRD analysis of these cells showed phase transitions from crystalline to amorphous type structure, and ex-situ FTIR proves the preservation of the CoS phase during the cycling. A redox reaction mechanism was suggested to explain the cells' battery performance by ex-situ XRD analysis.Öğe High-Performance Full Sodium Cells Based on MgO-Treated P2-Type Na0.67(Mn0.5Fe0.5)1-xCoxO2 Cathodes(Mdpi, 2023) Taskiran, Nermin; Altundag, Sebahat; Koleva, Violeta; Altin, Emine; Arshad, Muhammad; Avci, Sevda; Ates, Mehmet NurullahHerein, we design a cathode material based on layered Na-2/3(Mn1/2Fe1/2)O-2 for practical application by combining the Co substitution and MgO treatment strategies. The oxides are prepared via solid-state reactions at 900 degrees C. The structure, morphology, and oxidation state of transition metal ions for Co-substituted and MgO-treated oxides are carefully examined via X-ray diffraction, IR and Raman spectroscopies, FESEM with EDX, specific surface area measurement, and XPS spectroscopy. The ability of oxides to store sodium reversibly is analyzed within a temperature range of 10 to 50 degrees C via CV experiments, galvanostatic measurements, and EIS, using half and full sodium ion cells. The changes in the local structure and oxidation state of transition metal ions during Na+ intercalation are monitored via operando XAS experiments. It is found that the Co substituents have a positive impact on the rate capability of layered oxides, while Mg additives lead to a strong increase in the capacity and an enhancement of the cycling stability. Thus, the highest capacity is obtained for 2 at.%-MgO-treated Na-2/3(Mn1/2Fe1/2)(0.9)Co0.1O2 (175 mAh/g, with a capacity fade of 28% after 100 cycles). In comparison with Co substituents, the Mg treatment has a crucial role in the improvement of the lattice stability during the cycling process. The best electrode materials, with a chemical formula of 2 at.%-MgO treated Na-2/3(Mn1/2Fe1/2)(0.9)Co0.1O2, were also used for the full cells design, with hard carbon as an anode. In the voltage window of 2-4 V, the capacity of the cells was obtained as 78 mAh/g and 51 mAh/g for applied current densities of 12 mA/g and 60 mA/g, respectively.Öğe 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, SevdaNa-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.Öğe Investigation of electrochemical performance of Na-ion batteries by hard carbon anodes produced by biomass of Prunusarmeniaca seeds(Springer, 2023) Oktay, Zeynep Melek; Onal, Yunus; Depci, Tolga; Altundag, Sebahat; Altin, Serdar; Yasar, Sedat; Altin, EmineHard carbon is successfully fabricated using biomass of Prunusarmeniaca seed shells, and its structural properties are examined by different spectroscopic techniques. For using as an anode electrode in Na-ion batteries, the material is subjected to further pyrolysis at varying temperatures for achieving the necessary levels of conductivity and surface area which are important features for electrode materials. Distinguish properties of the hard carbon in the XRD study appeared as broad peaks at 2 & theta; = 23 & DEG; and 43 & DEG;. The purity of produced hard carbons was approved by EDX to analyze that the purity of hard carbon is greater than 99.9%, making it suitable for industrial use. It was found that the CV curves of the cells created in this work utilizing hard carbon were quite comparable to the CV curves of commercially produced hard carbon cells. According to charge/discharge cycling measurements for constant current at rt, the highest capacity of 210.2 mAh/g using 0.1 A/g is obtained for the material pyrolyzed at 1200 & DEG;C and the capacity fade was found as 0.11. From these promising results, it is thought that the produced hard carbon can be easily used in the production of anode electrodes in commercial Na-ion batteries and technological applications. So it is summarized that P. armeniaca seed shells is one of the main sources for the production of the hard carbon and it can be used as an anode materials in battery cells.Öğe Investigation of structural and electrochemical performance of Ru-substituted LiFePO4 cathode material: an improvement of the capacity and rate performance(Springer, 2022) Yolun, Abdurrahman; Altin, Emine; Altundag, Sebahat; Arshad, Muhammad; Abbas, Syed Mustansar; Altin, SerdarLiRuxFe1-xPO4 (where x = 0.01-0.12) samples are successfully fabricated by conventional solid-state reaction technique and the structural properties are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FTIR) measurements. The XRD analysis shows that the minor impurity phases of RuO2 and LiRuO2 are observed for x >= 0.05 samples. Furthermore, the lattice volume is decreased with increasing Ru-content in the structure. The Ru-substituted battery cells exhibit similar cycling voltammetry (CV) data with the unsubstituted LiFePO4 battery cells. According to the charging/discharging cycles measurements for C/3-rate, the best capacity (147.58 mAh g(-1)) is obtained for LiFe0.93Ru0.07PO4 with a capacity fade of 0.0084 per cycle. It is found that Ru-substituted LiFePO4 has maximum C-rate when we analogize with the pristine LiFePO4 and the battery cycling performance is investigated for 4 C-rate up to 100 cycles and 3 and 4 C-rate up to 1000 cycles and it is found that Ru-substituted LiFePO4 exhibits excellent electrochemical performance such as 122, 84.5, and 53.1 mAh g(-1) for 1st, 500th, and 1000th cycles at 4 C-rate.Öğe 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, AliTi-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.Öğe Investigations of the capacity fading mechanism of Na0.44MnO2via ex situ XAS and magnetization measurements(Royal Soc Chemistry, 2018) Altin, Serdar; Oz, Erdinc; Altin, Emine; Demirel, Serkan; Bayri, Ali; Avci, SevdaNa-ion batteries represent a promising complementary alternative to Li-ion batteries due to their high energy density and natural abundancy of Na. However, these batteries have short cycle life and extensive research activities on these batteries are required to understand the mechanism of such drawbacks. In this report, we investigate the capacity fading mechanism of Na(0.44)MnO(2)via ex situ X-ray diffraction, X-ray absorption spectroscopy, Fourier transform infrared spectroscopy and magnetization measurements. Our results show that the unit cell volume, the effective mass of Mn-O bonds, the number of Mn4+ ions and the effective magnetic moment decrease upon repeated cycling. We propose that some Mn4+ ions in the octahedral environment become Mn3+ ions in a square pyramidal environment, causing oxygen release upon cycling. Any free oxygen in the battery is expected to react with the electrolyte and cause capacity fade.Öğe Magnetic and thermoelectric properties of B-substituted NaCoO2(Springer Heidelberg, 2015) Altin, Emine; Oz, Erdinc; Demirel, Serkan; Bayri, AliWe report the structural, electrical, thermal and magnetic properties of NaCo1-xBxO2 from 300 K down to 5 K. XRD analysis shows that B ions successfully incorporate in the crystal structure for x < 0.25. The resistivity of the samples increases with increasing B content and the transport mechanism change for x = 0.5. The highest thermopower value is obtained for x = 0.5 sample, and the thermoelectric behavior at low temperature is explained by Mott approximation. The experimentally obtained thermal conductivity data are analyzed by this model including the carrier thermal term, kappa(c), and the lattice thermal conductivity term, kappa(L). We found that phonon-phonon interaction and point defect contribution to kappa are affected by the B content and the temperature. The Co valance states are analyzed by Heike formula, and the effective magnetic moment is determined by these values. The chi-T curves of the samples are fitted by Curie-Weiss law, and the obtained mu(eff) values match well with the theoretically calculated values (0.9 mu(B)/Co). We observed a strong correlation between magnetic properties and thermopower.Öğe 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, MessaoudHerein, 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.Öğe P2-type Na0.67Mn0.5-xVxFe0.43Ti0.07O2 powders for Na-ion cathodes: Ex-situ structural analysis and full-cell study(Pergamon-Elsevier Science Ltd, 2024) Dogan, Ebru; Altundag, Sebahat; Altin, Emine; Oz, Erdinc; Altin, SerdarThis study used a modified solid-state synthesis technique to synthesize Na0.67Mn0.5-xVxFe0.43Ti0.07O2 (x = 0.02 0.1) cathode materials. The XRD pattern shows that there are no impurity phases in the samples for x <= 0.06. The granular grain formation was observed in each sample and the largest surface area was obtained for x = 0.06 Vdoped composition. According to XPS analysis of the x = 0.06 sample, the V and Ti ions have three different valence states in the structure and the ratio of V3+/V4+/V5+ ions in the powders was calculated as 13 %/36 %/51 % and the spin splitting binding energy gaps were found as 7.1 eV for each V-ions and they affected by cycling process. The redox mechanism of the half cells was investigated at 10 degrees C and room temperature. The diffusion coefficient values of Na+ were calculated by cycling voltammetry (CV) and GITT techniques for the x = 0.06. Although the highest capacity of the half cells for the V-substituted samples was found to be 188.3 mAh/g for x = 0.02 V-doping in the cells for C/3-rate, the best capacity fade among the cells was obtained for x = 0.06 as 36.9 %. The ex-situ analysis of the electrodes after 100 cycles at the environmental temperatures of 10 degrees C, 50 degrees C, and 60 degrees C was investigated and it was found that the valence state of the elements changed by the cycling process. The artificial solid electrolyte interface (SEI) formation on the anode surface was performed by presodiation technique and the full cells were assembled using Na0.67Mn0.44V0.06Fe0.43Ti0.07O2/hard carbon architecture and the obtained first capacity values for C/3-rate were 90.1 mAh/g and 66.6 mAh/g, respectively, and the capacity value decreased with the cycling process up to 60 cycles and then gave a plateau with increasing cycle numbers up to 500 cycles.Öğe Production of Pb-doped LiFePO4 and analysis of their electrochemical performance(Springer, 2023) Gultek, Ezgi; Altundag, Sebahat; Altin, Serdar; Altin, EmineIn this study, LiFe1-xPbxPO4 (x = 0-0.12) powders were successfully produced by solid-state technique. The XRD patterns of the samples exhibit that the main phase is LiFePO4 with minor impurity phases of PbO and Fe2O3 in the structure, in which the phase ratio of PbO increases with increasing doping content. Four probe electrical resistance measurements showed that resistance decreases from 111 kO to 37 kO when increasing Pb-content; however, CV measurement indicated that redox peak wideness increased for x = 0.09, unwanted behavior for the battery cells. The galvanostatic cycles at C/2-rate yielded the highest capacity value of 121.6 mAh/g at room conditions with 1.06% capacity fade over 100 cycles when using x = 0 0.06 sample-better than undoped cells-while C-rate tests confirmed promising results for LiFePO4 cells using same sample concentration level.Öğe Production of V-Doped P2-type Na0.67Mn0.5Fe0.43Al0.07O2 Cathodes and Investigation of Na-Ion Full Cells Performance(Wiley-V C H Verlag Gmbh, 2024) Dogan, Ebru; Altundag, Sebahat; Altin, Serdar; Arshad, Muhammad; Balci, Esra; Altin, EmineThe Na0.67Mn0.5Fe0.43Al0.07O2(x = 0-0.1) samples are successfully produced and their structural properties are investigated by common techniques. The highest surface area is found as 4.94 m(2) g(-1) for x = 0.04 V by the Brunauer-Elmet-Teller analysis. According to X-ray photoelectron spectroscopy of x = 0.04 V-doped sample,V4+, and V5+ ions are formed in the structure. The main phase is observed as P63/mmc symmetry with an impurity phase of V6O13 for x >= 0.06 . According to the CV analysis, while the redox voltage decreases for the Mn3+/Mn4+ , the intensity of the peaks of Fe2+/Fe3+ redox reaction decreases. While the best capacity value of the half cells at C/3-rate is obtained as 171 mAh g(-1) for x = 0.04, the lowest capacity fade is found for x = 0.08 . It is mentioned the V6O13 may contribute to the electrochemical process . The galvanostatic tests are investigated for the voltage windows of 3.5-1.5, 4-1.5, 4-2.5, 4-2, and 4-2.5 V and it is seen that the battery cells for 3.5-1.5 V have the best capacity fade (6%) among the others. The Na0.67Mn0.5Fe0.43Al0.07O2/ hard carbon is used for the full cells with presodiated anode and the first capacity value of the full cell is obtained as 80.2 mAh g(-1) for C/2-rate.Öğe Structural, magnetic, electrical, and electrochemical properties of Sr-Co-Ru-O: A hybrid-capacitor application(Wiley, 2018) Altin, Serdar; Bayri, Ali; Demirel, Serkan; Oz, Erdinc; Altin, Emine; Avci, SevdaIn this study, we report the synthesis of SrCo1-xRuxO3- nominal compositions, where x=0.0-1.0, using solid-state reaction technique. XRD analysis confirms the structure of x=0 sample as hexagonal Sr6Co5O15. As the Co ions are substituted by Ru, a two-phase structure (hexagonal R32 and orthorhombic Pbnm) emerges up to x0.5. As the Ru content is increased further, the hexagonal R32 phase disappears completely and an orthorhombic Pbnm phase becomes the main phase. SEM images show that grain size of the samples decreases with increasing Ru content. Temperature-dependent electrical conductivity studies indicate upon Ru substitution in the nominal SrCo1-xRuxO3- compounds, resistivity decreases due to appearance of metallic SrRuO3 phase. The cyclic voltammogram (CV) of the samples show capacitive properties upon Ru substitution. The cycle measurements of the capacitors yield promising results for potential supercapacitor applications.Öğe Thermally Induced Spin State Transition in LiCoO2 and Its Effects on Battery Performance(Pergamon-Elsevier Science Ltd, 2017) Oz, Erdinc; Demirel, Serkan; Altin, Serdar; Altin, Emine; Bayri, Ali; Avci, SevdaLiCoO2 is the most widely used and extensively studied cathode material for Li-ion batteries. The studies based on the improvement of the performance have focused on the structural and electrochemical properties of LiCoO2. However, significantly less attention has been paid to its magnetic properties and their effects on battery performance. For the first time to our knowledge, we report a thermally induced magnetic spin state transition from low spin (LS) to intermediate spin (IS) at similar to 800 K in bulk LiCoO2 via magnetic susceptibility measurements. We quench the LiCoO2 from above the spin state transition temperature (similar to 810 K) into liquid nitrogen to preserve the IS state at room temperature. We use this quenched sample (q-LiCoO2) as an active cathode material. We observe a significant improvement (similar to 15% better capacity retention after 200 cycles at 1C) in cell performance of q-LiCoO2 compared to the ref-LiCoO2 which is used as a reference material. Our results show that it is possible to tailor the magnetic properties and electronic structure of cathode materials to achieve better battery performance. (C) 2017 Elsevier Ltd. All rights reserved.
