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Öğe Energy storage performance of LiV3O8/water-in-salt electrolyte/LiNi1/3Co1/3Mn1/3O2 cell for aqueous lithium-ion batteries(Elsevier, 2022) Kunduracı, Muharrem; Kılıç Çetin, Selda; Çağlayan, Uğur; Mutlu, Rasiha Nefise; Kaya, Doğan; Ekicibil, AhmetElectrochemical performance of an aqueous lithium-ion battery containing LiV3O8 anode, ‘water-in-salt’ 20 M LiTFSI electrolyte and LiNi1/3Co1/3Mn1/3O2 cathode was studied. In the full cell, the cathode and anode reached a maximum lithiation capacity of 145.8 mAh g?1 and 80 mAh g?1, respectively. The full cell successfully underwent 100–110 cycles before hitting 20% capacity loss limit. The average discharge potential of the cell started at 0.849 V and stayed relatively stable in the next 140 cycles. The first cycle coulombic efficiency was as high as 80% and it stabilized at 99–100% in the subsequent cycles. These are the best numbers ever reported for this anode/cathode couple. This outperformance was achieved thanks to the increased stability of the anode and cathode materials in high molarity ‘water-in-salt’ electrolyte over lower molarity nitrate or sulfate electrolytes previously reported in literature.Öğe Long-life (Co, Al, Mg)-doped LiMn1.5Ni0.5O4 cathodes prepared by co-precipitation method(Springer Science and Business Media Deutschland GmbH, 2024) Kunduracı, Muharrem; Boyacı, Hilmi; Görmez, Özkan; Çağlayan, Uğur; Çirmi, Doğan; Özkendir, Osman Murat; Harfouche, Messaoud; Gözmen, BelginThe spinel cathode LiMn1.5Ni0.5O4 (LMN) is garnering significant interest in the realm of lithium-ion batteries owing to its economical nature, elevated operating voltage, high theoretical energy density, and commendable thermal stability at a charged state. Various doping elements have been suggested to enhance the discharge capacity and prolong the lifetime of the LMN cathode. In this study, three doping elements (cobalt, aluminum, and magnesium) are investigated and compared using different characterization techniques. All three elements proved to be effective in extending the cycle life. Among all three elements, cobalt exhibits the highest threshold for dopant concentration beyond which performance degradation initiates. The cathode material with the highest performance, LiMn1.5Ni0.4Co0.1O4, is projected to have a cycle life of 900 cycles, contrasting with the 500 cycles of the undoped sample.Öğe Significance of surface roughness in the supercapacitor activity of nickel-based electrodes(Springer, 2021) Kunduracı, Muharrem; Çirmi, Doğan; Doğan Çalhan, Selda; Çağlayan, UğurNickel-based thin film electrodes were electrodeposited onto copper substrate using a deep eutectic solvent. The supercapacitor performance of these electrodes in alkaline KOH solution was greatly enhanced by altering surface roughness of coatings. In order to create a rougher surface, two paths were followed. In the first path, Ni-only coatings were prepared at different deposition potentials and smooth-to-rough transition in surface morphology took place at higher potentials due to increasing emission of hydrogen bubbles. In the second path, Ni-Zn binary coatings with varying zinc concentration were electrodeposited and surface roughness was formed by dealloying zinc element from the electrodes as corroborated by Scanning Electron Microscopy and Atomic Force Microscopy results. In both paths, noticeable improvements in the capacitance of nickel electrodes were observed upon the apperance of rougher surface. A linear relationship was discovered between cathodic peak currents and polarization values in the cyclic voltammetry scans of electrodes, possibly for the first time here in literature. The increase in polarization was explained by the decrease in electrode conductivity proved by dwindling of metallic nickel peaks in X-ray diffraction upon electrochemical testing.Öğe Spherical and core–shell-structured LiMn1.5Ni0.5O4 lithium-ion battery cathode with enhanced cyclability(Springer, 2022) Kunduracı, Muharrem; Çağlayan, UğurSpherical LiMn1.5Ni0.5O4(LMN) spinel materials with Co or Al doping were synthesized using coprecipitation technique and the dopants’ impacts on cathode performance were explored. While both dopants were conducive to the capacity retention of LMN spinel, aluminum was more efective. Cobalt doping also helped increase the discharge capacity of control spinel, unlike aluminum. Core–shell-structured materials with Co-doped core and Al-doped shell segments were synthesized with the aim to create synergy between two dopants. Indeed, the best cathode performance in terms of lithium capacity and cyclability was reached with core–shell material. The best cathode material denoted as CS 3-1 had a frst cycle lithium capacity of 133.1 mAh g?1 and exhibited capacity fade rate of 0.08% per cycle. X-ray difraction and FTIR studies revealed that all cathode materials were single phase and spinel type with Fd3m space group. Focused-ion beam (FIB) and Scanning Electron Microscope photos showed that spinel materials were made of distinct spherical particles 3–4 µm in diameter. The core–shell structure was also substantiated with the photos. Energy dispersive analysis confrmed that constituent elements Mn, Ni, Co and Al had a homogeneous distribution within spherical particles. Electrochemical impedance spectroscopy results showed that Al doping on the surface was benefcial to reducing impedance growth, thereby explaining the better cyclability and rate performance of these cathodes.
