Browsing by Author "Ikeda, K"

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    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.
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    Ultralow thermal conductivity from transverse acoustic phonon suppression in distorted crystalline α-MgAgSb
    (Springer Nature, 2020-02-18) Li, XY; Liu, PF; Zhao, EY; Zhang, ZG; Guidi, T; Le, MD; Avdeev, M; Ikeda, K; Otomo, T; Kofu, M; Nakajima, K; Chen, J; He, LH; Ren, Y; Wang, XL; Wang, BT; Ren, ZF; Zhao, HZ; Wang, FW
    Low thermal conductivity is favorable for preserving the temperature gradient between the two ends of a thermoelectric material, in order to ensure continuous electron current generation. In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic in PbTe and SnSe, and phonon scattering resulting from the dynamic disorder in AgCrSe2 and CuCrSe2, which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in α-MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the compound’s intrinsic distorted rocksalt sublattice, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in α-MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials. © The Author(s) 2020.