Browsing by Author "Park, I"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    High‐voltage‐driven surface structuring and electrochemical stabilization of Ni‐rich layered cathode materials for Li rechargeable batteries
    (Wiley, 2020-05-04) Song, SH; Cho, M; Park, I; Yoo, JG; Ko, KT; Hong, J; Kim, J; Jung, SK; Avdeev, M; Ji, S; Lee, S; Bang, J; Kim, H
    Layered lithium–nickel–cobalt–manganese oxide (NCM) materials have emerged as promising alternative cathode materials owing to their high energy density and electrochemical stability. Although high reversible capacity has been achieved for Ni‐rich NCM materials when charged beyond 4.2 V versus Li+/Li, full lithium utilization is hindered by the pronounced structural degradation and electrolyte decomposition. Herein, the unexpected realization of sustained working voltage as well as improved electrochemical performance upon electrochemical cycling at a high operating voltage of 4.9 V in the Ni‐rich NCM LiNi0.895Co0.085Mn0.02O2 is presented. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni2+O rock‐salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling. The manifestation of the layered Ni2+O rock‐salt phase along with the structural evolution related to the metal dissolution are probed using in situ X‐ray diffraction, neutron diffraction, transmission electron microscopy, and X‐ray absorption spectroscopy. The findings help unravel the structural complexities associated with high working voltages and offer insight for the design of advanced battery materials, enabling the realization of fully reversible lithium extraction in Ni‐rich NCM materials. © 2020 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
  • No Thumbnail Available
    Item
    Rational design of Li off-stoichiometric Ni-rich layered cathode materials for Li-ion batteries
    (Elsevier, 2022-11) Song, SH; Hong, S; Cho, M; Yoo, JG; Jin, HM; Lee, SH; Avdeev, M; Ikeda, K; Kim, J; Nam, SC; Yu, SH; Park, I; Kim, H
    The electrification trend in the automotive industry is fueling research on Ni-rich layered NCM cathode materials with high specific capacities. The simplest way to maximize the electrochemical performance of Ni-rich NCM is to tune the crystal structure by controlling the Li content and synthesis temperature. Herein, we demonstrate the critical roles of the Li content and synthesis temperature in determining the crystal structure of Li-excess Ni-rich NCM with enhanced electrochemical performance. The crystal structure of Li-excess Ni-rich NCM was systemically investigated using X-ray diffraction, neutron diffraction, and X-ray absorption spectroscopy, revealing that excess Li can be accommodated in Ni-rich NCM as the synthesis temperature decreases, resulting in stable cycle performance at high working voltage. We believe that our findings provide a rational reason for the excess amount Li required for optimization of the synthesis of Ni-rich NCM and offer insight for the simplest design of Ni-rich cathode materials that are stable under high-voltage operation. © 2022 Elsevier B.V.