• OZGUL KELES

      Articles written in Bulletin of Materials Science

    • Improving electrochemical performance of tin-based anodes formed via oblique angle deposition method

      B Deniz Polat Ozgul Keles

      More Details Abstract Fulltext PDF

      An oblique angle electron beam co-deposition technique was used to fabricate nanostructured Sn-based thin films: Sn, Cu–Sn and Cu–Sn–C. The morphological and structural properties of the films were observed via scanning electron microscopy (SEM) and thin film X-ray diffraction (XRD) methods. The electrochemical (CV and EIS) and the galvanostatic test results demonstrated that the addition of Cu with or without C affected the electrochemical performance of the thin film positively since Cu and C improved both the mechanical and the electrical properties of the nanostructured Sn thin film electrode. The high cycleability and capacity retention were achieved when the nanostructured Cu–Sn–C thin film was used as an anode material since C increased the mechanical tolerance of the thin film to the volume expansion due to its grain refiner effect. Cu not only improved the electrical conductivity and the adhesion of the film to substrate but also the mechanical tolerance of the film with its ductile property.

    • Effects of sonication power on electrochemical performance of ZrO$_2$-decorated LiMn$_2$O$_4$ cathode material for LIBs

      MEHMET EMRE CETINTASOGLU OZGUL KELES

      More Details Abstract Fulltext PDF

      The LiMn$_2$O$_4$ (LMO) powder is decorated with ZrO$_2$ (denoted as Zr@LMO) particles by using sonicationassisted sol–gel method. Different sonication powers (10, 30 and 50%) are used to disperse ZrO$_2$ and the effects of ZrO$_2$ distribution at LiMn$_2$O$_4$'s electrochemical performance are analysed. Scanning electron microscopy and energy dispersive spectroscopy analyses have been made on laminated samples. For the structural analyses of particles, X-ray diffractometer is used. Electrochemical performances of electrodes are tested with galvanostatic measurements, cyclic voltammograms and electrochemical impedance spectroscopy. The ZrO$_2$ distribution ratio on the particle surfaces is improved by 10% with the increase of sonication power from 10 to 50%. Therefore, at 50% sonication power, lower charge transfer resistance and side reactions (Mn dissolution) are accomplished, which leads to 41 and 9% specific capacity increase compared to pure and the lowest sonication power, respectively. After 100 cycles at 0.1C, 93.2 mAh g$^{–1}$ specific discharge capacity and 73.4% capacity retention are attained for ZrO$_2$-decorated LMO at 50% sonication power. Furthermore, at 2C rate, the specific discharge capacity of the decorated sample at 50% sonication power is 59% higher than the pure LMO.

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      Posted on October 12, 2020

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      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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