Journal of Energy Chemistry ›› 2023, Vol. 86 ›› Issue (11): 559-568.DOI: 10.1016/j.jechem.2023.07.041

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Doping of group IVB elements for nickel-rich cobalt-free cathodes

Shengnan Guoa, Xincheng Leia,b, Jiayi Wanga, Jie Suc,d, Yingying Wanga, Xiaozhi Liua, Pengxiang Jia,b, Kangning Zhaoa, Xuefeng Wanga,b, Lin Gue, Zhenpeng Yaoc,d, Dong Sua,b   

  1. aNational Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
    bUniversity of Chinese Academy of Sciences, Beijing 100049, China;
    cCenter of Hydrogen Science, Shanghai Jiao Tong University, Shanghai 200240, China;
    dState Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
    eBeijing National Center for Electron Microscopy and Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
  • Received:2023-06-23 Revised:2023-07-20 Accepted:2023-07-21 Online:2023-11-15 Published:2023-11-07
  • Contact: *E-mail addresses: z.yao@sjtu.edu.cn (Z. Yao), dongsu@iphy.ac.cn (D. Su).
  • About author:1These authors contributed equally to this work.

Abstract: Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries. To make doping effective, it is important to understand the mechanism of how the dopants regulate the electronic band, lattice parameter adjusting, or hetero-phase formation to achieve high stability. In this study, we investigate LiNi0.9Mn0.1O2 cathodes doped with IVB grouping elements via multiple characterization techniques. By utilizing in situ XRD and TEM methods, we found that the stronger Ti-O bond effectively improves the cathode stability via a dual protection mechanism. Specifically, the bulk lattice of cathode is well-preserved during cycling as a result of the suppressed H2-H3 phase transition, while a in situ formed Ti-rich surface layer can prevent continuous surface degradation. As a result, the 5% Ti doped LiNi0.9Mn0.1O2 cathode exhibits a high capacity retention of 96% after 100 cycles. Whereas, despite IVB group elements Zr and Hf have stronger bonding energy with oxygen, their larger ionic radii actually impede their diffusion into the cathode, thereby they can not improve the cycling stability. Our findings uncover the functional origin of doped elements with their dynamic modification on cathode structure, providing mechanistic insights into the design of nickel-rich cobalt-free cathodes.

Key words: Li ion battery, Layered cathode, Cycling stability, Doping effect, In situ XRD