Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, ChemistrySubject: search.filters.subject.Lithium ion batteries

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  • Master Thesis
    Doping Effect on the Anode Material Capability of 2d Bn Nanosheets
    (01. Izmir Institute of Technology, 2024) Elmacı Irmak, Nuran; Özdemir, Mustafa Coşkun; Irmak, Nuran Elmacı; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis, the potential of BNN surfaces doped with Al, Cl, Co, Fe, Ga, O, P, and S atoms as anode materials in K, Li, Mg, and Na ion batteries was investigated. Semi-empirical tight-binding combined with meta-dynamics methods and density functional theory were utilized to discover these properties. The effects of doping atoms on the electronic structure and geometry of BNN surfaces were also studied. Changes in the electronic structure and conductivity were reported by examining the HOMO-LUMO orbitals and the energy differences between these orbitals. Using previously reported experimental data and examining similar studies from the literature, the atoms to be doped were chosen. While vacancies at the sites of boron atoms in single-layer boron-nitride nanosheets were observed, vacancies formed by nitrogen atoms were not observed, indicating that boron vacancies are much more likely for the doping position. So that doping was performed on the boron atom. The level of quantum calculations used in this work was validated using experimental data. B3LYP/def2-SVP/D4/gCP level of theory is used for all calculations for BNN-nanosheets studied in this thesis. The bond lengths and the HOMO-LUMO energy difference were found to be nearly the same as the experimental data. The conductivity of the BNN surface was increased with the doping process. However, significant improvements are followed by doping of cobalt, iron, and sulfur atoms with 35%, 34%, and 26% alteration, respectively. For a suitable battery manufacture, the potential anode material should offer structures with high theoretical specific capacity, low anode electrode voltage, and minimal volume change between charged/discharged states. It was observed that none of the doped-BNN surfaces involved in this study were suitable for the use of anode material in magnesium ion batteries. On the other hand, they can be used as a negative electrode for potassium, lithium, and sodium batteries. Their capacity in lithium is better than Na and K batteries. Our results suggest that most of the doped BNN surface with ions studied in this thesis could be used as anode materials. However, none of them owns a better battery capacity than classic lithium batteries.
  • Master Thesis
    Synthesis and Characterization of High Nickel Content Cathode Materials for High Performance and Capacity Reach in Li-Ion Batteries
    (Izmir Institute of Technology, 2022) Karabudak, Engin; Karabudak, Engin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Due to their high energy density, low self-discharge properties, nearly negligible memory effect, high open-circuit voltage, and extended service life, lithium-ion batteries continue to gain interest as a promising energy storage technology. In the automotive industry, high-energy lithium-ion batteries have become the preferred power source for electric vehicles and hybrid electric vehicles in recent years. With the development of lithium-ion battery technology, several materials have been used into the cathodes and anodes in order to improve performance. LiNiCoAlO4, LiMn2O4, LiNiMnCoO4, Li4Ti5O12 and LiFePO4are five lithium-ion batteries that are commonly utilized in commercial EVs today. NMC cathode material is one of the most effective lithium-ion battery materials for balancing specific qualities. The battery cathode of NMC is strengthened with a specific ratio of three synthetic components (Nickel, Manganese and Cobalt). Depending on the proportions of these three chemical constituents, battery performance can vary. Synthesis, characterisation, and electrochemical studies of cathode materials with a high Nickel content were performed in this project in an effort to boost the specific capacity and durability of Li-ion batteries. In these preliminary studies, the synthesis and characterization of Ni(OH)2 structures, which serve as a starting material for the synthesis of cathode materials with a high Nickel content, was also a goal. In the research, the spherical Ni(OH)2 structure was effectively synthesized, and excellent electrochemical results were achieved. SEM and XRD analyses were performed on the resulting products.
  • Master Thesis
    Synthesis and Characterization of Aluminum Doped To Extend Cathode Life in Li-Ion Batteries
    (01. Izmir Institute of Technology, 2021) Karabudak, Engin; Karabudak, Engin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Lithium-ion batteries have an important place in meeting the energy needs and are of greater importance than their cognates, thanks to their characteristics as secondary batteries. Volumetric and gravimetric energy densities are the main features that carry lithium-ion batteries to the top. Lithium-ion batteries consist of different parts: cathode, anode, separator and electrolyte. While the anode materials are generally based on silicon, carbon and tin, the cathode materials include layered LiCoO2, spinel LiMn2O4, olivine LiFePO4, layered LiNi0,8Co0,15Al0,05O2(NCA) and layered LiNiCoMnO2 (NMC). Nmc and nca cathode materials stand out due to their high energy densities. Of course, lithium-ion batteries also have some disadvantages. A prime example of this is the capacity reductions it experiences with the increasing number of cycles. The main reasons for the decrease in capacity are; The transformation of the layered structure into spinel structure, the contamination of the Lio structure on the cathode to the electrolyte structure as a result of the side reactions that occur, damage the stable structure of the electrolyte and lead to Li loss. Metal oxide surface modification methods come to the fore in studies conducted to prevent these disadvantages. In this study, nmc structure was synthesized by reprecipitation method. Xrd, and sem analyzes of the obtained structure were taken. Al2O3 surface modification method was applied on the cathode surface. Cyclic voltammetry analyzes of the nmc structures with and without the modification applied were made with the help of potentiometry and the results were compared.