Journal of Energy Chemistry ›› 2023, Vol. 85 ›› Issue (10): 126-136.DOI: 10.1016/j.jechem.2023.05.048

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Unveiling the parasitic-reaction-driven surface reconstruction in Ni-rich cathode and the electrochemical role of Li2CO3

Jiyu Caia,*, Zhenzhen Yanga, Xinwei Zhoub, Bingning Wanga, Ana Suzanac, Jianming Baid, Chen Liaoa, Yuzi Liub, Yanbin Chene, Shunlin Songe, Xuequan Zhange, Li Wangf, Xiangming Hef, Xiangbo Mengg, Niloofar Karamih, Baasit Ali Shaik Sulaimanh, Natasha A. Chernovah, Shailesh Upretih, Brad Preveli, Feng Wang, Zonghai Chena,*   

  1. aChemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA;
    bCenter for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA;
    cCondensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA;
    dEnergy and Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA;
    eBeijing Easprint Material Technology Co. Ltd., Beijing 100160, China;
    fInstitute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;
    gDepartment of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701, USA;
    hCharge CCCV (C4V), 45 Murray Hill Road, Center of Excellence, Binghamton University, Vestal, NY 13850, USA;
    iPrimet Precision Materials, 950 Danby Road, Ithaca, NY 14850, USA;
    jApplied Materials Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
  • Received:2023-04-19 Revised:2023-05-27 Accepted:2023-05-31 Online:2023-10-15 Published:2023-11-06
  • Contact: *E-mail addresses: jcai@anl.gov (J. Cai), zonghai.chen@anl.gov (Z. Chen).

Abstract: Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energy-density lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li2CO3 impurity content on LiNi0.83Mn0.1Co0.07O2 cathodes using air, tank-air, and O2 synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li2CO3 impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li2CO3 content and severe performance deterioration of Ni83 cathodes. The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Ni-rich cathodes and prepares us for searching for rational strategies.

Key words: Ni-rich cathodes, Surface reconstructions, Phase transformation, Parasitic reactions, Li2CO3