Browsing by Author "Dupre, N"
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- ItemControlled atomic solubility in Mn‐rich composite material to achieve superior electrochemical performance for Li‐ion batteries(Wiley, 2019-12-16) Lee, J; Zhang, Q; Kim, J; Dupre, N; Avdeev, M; Jeong, M; Yoon, WS; Gu, L; Kang, BThe quest for high energy density and high power density electrode materials for lithium-ion batteries has been intensified to meet strongly growing demand for powering electric vehicles. Conventional layered oxides such as Co-rich LiCoO2 and Ni-rich Li(NixMnyCoz)O2 that rely on only transition metal redox reaction have been faced with growing constraints due to soaring price on cobalt. Therefore, Mn-rich electrode materials excluding cobalt would be desirable with respect to available resources and low cost. Here, the strategy of achieving both high energy density and high power density in Mn-rich electrode materials by controlling the solubility of atoms between phases in a composite is reported. The resulting Mn-rich material that is composed of defective spinel phase and partially cation-disordered layered phase can achieve the highest energy density, ≈1100 W h kg−1 with superior power capability up to 10C rate (3 A g−1) among other reported Mn-rich materials. This approach provides new opportunities to design Mn-rich electrode materials that can achieve high energy density and high power density for Li-ion batteries. © 1999-2021 John Wiley & Sons, Inc.
- ItemFully exploited oxygen redox reaction by the inter‐diffused cations in Co‐free Li‐rich materials for high performance Li‐ion batteries(Wiley, 2020-09-09) Lee, J; Dupre, N; Jeong, M; Kang, SY; Avdeev, M; Gong, Y; Gu, L; Yoon, WS; Kang, BTo meet the growing demand for global electrical energy storage, high-energy-density electrode materials are required for Li-ion batteries. To overcome the limit of the theoretical energy density in conventional electrode materials based solely on the transition metal redox reaction, the oxygen redox reaction in electrode materials has become an essential component because it can further increase the energy density by providing additional available electrons. However, the increase in the contribution of the oxygen redox reaction in a material is still limited due to the lack of understanding its controlled parameters. Here, it is first proposed that Li-transition metals (TMs) inter-diffusion between the phases in Li-rich materials can be a key parameter for controlling the oxygen redox reaction in Li-rich materials. The resulting Li-rich materials can achieve fully exploited oxygen redox reaction and thereby can deliver the highest reversible capacity leading to the highest energy density, ≈1100 Wh kg−1 among Co-free Li-rich materials. The strategy of controlling Li/transition metals (TMs) inter-diffusion between the phases in Li-rich materials will provide feasible way for further achieving high-energy-density electrode materials via enhancing the oxygen redox reaction for high-performance Li-ion batteries. © 2020 The Authors.
- ItemSuperior rate capability and cycling stability in partially cation-disordered Co-free Li-rich layered materials enabled by an initial activation process.(American Chemical Society, 2021-06-22) Lee, JH; Yang, YJ; Jeong, MH; Dupre, N; Avdeev, M; Yoon, WS; Choi, SY; Kang, BWLi-rich layered materials that have Co-free and Mn-rich 3d-transition metals have the potential to increase the achievable energy density of batteries because they are inexpensive and yield high capacity by exploiting an additional oxygen redox reaction. However, these have low electrochemical activity and sustainability, with severe voltage fade, rapid capacity decay, and poor rate capability. Here, we report sustainable cycling stability and fast rate capability of Co-free Li2MnO3-based Li-rich layered materials that are governed by the electrochemical activation process during the 1st cycle and that this process can be controlled by the degree of the cation disordering in the pristine material. From the comparative study of two samples that have different degrees of cation disordering in the same composition, an increase in cation disordering in the pristine material strongly improves its tolerance to structural changes in the bulk and on the surface during the activation process at the 1st cycle, leading to less structural changes for subsequent cycles. As a result, high electrochemical activity and superior rate capability in subsequent cycles can be achieved even with the cation disordering in the pristine. Furthermore, we verified the findings by developing an additional material that had higher cation disordering in the pristine structure than the samples tested and showing that the additional sample has improved rate capability and cycle retention. This understanding that sustainable electrochemical characteristics are governed by an activation process in the 1st cycle, which can be controlled by a structural feature of the pristine material, will be useful in the design of low-cost, Li-rich layered materials that can achieve sustainable high energy density and fast rate capability for Li-ion batteries. © 2021 American Chemical Society
- ItemUnderstanding the cation ordering transition in high-voltage spinel LiNi0.5Mn1.5O4 by doping Li instead of Ni(Springer Nature, 2017-07-27) Lee, J; Dupre, N; Avdeev, M; Kang, BWe determined how Li doping affects the Ni/Mn ordering in high-voltage spinel LiNi0.5Mn1.5O4(LNMO) by using neutron diffraction, TEM image, electrochemical measurements, and NMR data. The doped Li occupies empty octahedral interstitials (16c site) before the ordering transition, and can move to normal octahedral sites (16d (4b) site) after the transition. This movement strongly affects the Ni/Mn ordering transition because Li at 16c sites blocks the ordering transition pathway and Li at 16d (4b) sites affects electrostatic interactions with transition metals. As a result, Li doping increases in the Ni/Mn disordering without the effect of Mn3+ ions even though the Li-doped LNMO undergoes order-disorder transition at 700 °C. Li doping can control the amount of Ni/Mn disordering in the spinel without the negative effect of Mn3+ ions on the electrochemical property. © 2021 Springer Nature Limited. Provided by the Springer Nature SharedIt content-sharing initiative.