• SUKEUN YOON

      Articles written in Bulletin of Materials Science

    • Ammonolysed LiNi$_{0.8}$Co$_{0.15}$Al$_{0.05}$O$_2$ as a cathode material for Li-ion batteries with improved rate capability

      SUKEUN YOON

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      In this work, ammonolysed LiNi$_{0.8}$Co$_{0.15}$Al$_{0.05}$O$_2$ (NCA) prepared by co-precipitation and subsequent ammonolysis was investigated as a cathode material for Li-ion batteries with enhanced rate capability. Detailed structural and morphological property characterization demonstrated that ammonolysis results in the incorporation of a small amount of nitrogen into the surface layer of the afore-mentioned material. The electrochemical performances of NCA electrodes were measured by galvanostatic charging–discharging of the corresponding Li-ion cells, revealing that ammonolysed NCA exhibited higher capacity and rate capability than those of the pristine sample, i.e., after 20 cycles, the discharge capacity of the former equalled 176 mA h g$^{−1}$ at a current density of 18.4 mA g$^{−1}$, remaining as high as 107 mA h g$^{−1}$ at a high current density of 1840 mA g$^{−1}$. This improved performance was ascribed to ammonolysis-induced surface changes, which reduced cell polarization during cycling and enhanced the electrochemical stability and reaction kinetics of NCA electrodes.

    • tert-Butylamine borane as a reductant in electroless nickel plating for improved etch resistance in the electrolyte

      SOLLEE KIM SUKEUN YOON

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      An Ni–B coating was developed on a copper substrate by the direct electroless technique and from a plating bath containing tert-butylamine borane (TBAB). The influence of the electroless plating conditions, using TBAB as a reducing agent on the composition, surface morphology, high-temperature stability and etch resistance in the electrolyte of the coatings, was investigated. The resulting electroless Ni–B plating surfaces were examined and characterized by scanning electron microscopy and X-ray fluorescence spectroscopy for morphology and chemical composition, respectively.Electrochemical characterization by potentiodynamic polarization confirmed that a 0.1 M nickel concentration bath for the Ni–B plating was optimized by a TBAB concentration of 0.03 M, temperature of 60$^{\circ}$C and pH of 8. Under theoptimal bath conditions, the Ni–B electroless plating layer exhibited superior etch resistance in the electrolyte as well as improved stability at high temperature than the Ni–B electroless plating layer prepared using dimethylamine borane.Hence, owing to the remarkable properties of the Ni–B electroless plating layer, this fabrication technique that employs TBAB can be extended to fabricate other Ni–B electroless plating layers.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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