Journal of Energy Chemistry ›› 2023, Vol. 85 ›› Issue (10): 144-153.DOI: 10.1016/j.jechem.2023.06.009

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Unexpected Li displacement and suppressed phase transition enabling highly stabilized oxygen redox in P3-type Na layered oxide cathode

Myungeun Choia,b,1, Hobin Ahna,b,1, Hyunyoung Parka,b, Yongseok Leea,b, Jinho Ahna,b, Bonyoung Kua,b, Junseong Kima,b, Wonseok Koa,b, Jungmin Kanga,b, Jung-Keun Yooc, Duho Kimd,e,*, Jongsoon Kima,b,*   

  1. aDepartment of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea;
    bSKKU Institute of Energy Science and Technology (SIEST), Sungkyunkwan University, Suwon 16419, Republic of Korea;
    cCarbon Composites Department, Korea Institute of Materials Science (KIMS), Changwon 51508, Republic of Korea;
    dDepartment of Mechanical Engineering (Integrated Engineering Program), Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea;
    eDepartment of KHU-KIST Convergence Science and Technology, Kyung Hee University, 23, Kyunghee-daero Dongdaemun-gu, Seoul 02447, Republic of Korea
  • Received:2023-04-26 Revised:2023-06-07 Accepted:2023-06-10 Online:2023-10-15 Published:2023-11-06
  • Contact: *E-mail addresses: duhokim@khu.ac.kr (D. Kim), jongsoonkim@skku.edu (J. Kim).
  • About author:1These authors contributed equally to this work.

Abstract: Oxygen redox is considered a new paradigm for increasing the practical capacity and energy density of the layered oxide cathodes for Na-ion batteries. However, severe local structural changes and phase transitions during anionic redox reactions lead to poor electrochemical performance with sluggish kinetics. Here, we propose a synergy of Li-Cu cations in harnessing the full potential of oxygen redox, through Li displacement and suppressed phase transition in P3-type layered oxide cathode. P3-type Na0.7[Li0.1Cu0.2Mn0.7]O2 cathode delivers a large specific capacity of ∼212 mA h g-1 at 15 mA g-1. The discharge capacity is maintained up to ∼90% of the initial capacity after 100 cycles, with stable occurrence of the oxygen redox in the high-voltage region. Through advanced experimental analyses and first-principles calculations, it is confirmed that a stepwise redox reaction based on Cu and O ions occurs for the charge-compensation mechanism upon charging. Based on a concrete understanding of the reaction mechanism, the Li displacement by the synergy of Li-Cu cations plays a crucial role in suppressing the structural change of the P3-type layered material under the oxygen redox reaction, and it is expected to be an effective strategy for stabilizing the oxygen redox in the layered oxides of Na-ion batteries.

Key words: Layered oxide cathode, Oxygen redox reaction, Structural stability, Li displacement, No phase transition