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<p>Although the anionic activity in layered oxide positive electrodes is partially understood, the mechanism by which it induces internal crack propagation under high-voltage conditions remains unclear, severely limiting stable cycle life and available capacity. In this study, the mechanism underlying internal crack propagation is elucidated in LiCoO<sub>2</sub> under harsh float-charge conditions at 60 °C and a potential of 4.6 V vs. Li<sup>+</sup>/Li. We reveal that sequential phase transitions from O3 to O1 and then to a cation-mixed phase during deep Li<sup>+</sup> extraction generate significant lattice-mismatch stresses that initiate internal cracks. Crucially, the accompanying anionic activity drives the migration of the oxidized lattice O<sup><i>n−</i></sup> (0&#xa0;&lt;&#xa0;<i>n</i> &#xa0;&lt; &#xa0;2) towards these cracks, where it even accumulates as molecular O<sub>2</sub> that can be released upon crack propagation to the surface. It is identified that the sustained O1tocation-mixed phase transition and the bulk lattice O<sup><i>n−</i></sup> migration synergistically drive the interior crack propagation, ultimately leading to LiCoO<sub>2</sub> disintegration and electrochemical degradation. This work not only deepens our understanding of the anionic activity in layered positive electrodes but also provides mechanistic insights for the future design of stable LiCoO<sub>2</sub> positive electrodes.</p>

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Origin of crack propagation in lithium cobalt oxide positive electrode for lithium-ion batteries

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月10日

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  • Wenguang Zhao,
  • Zijian Li,
  • Mingyang Li,
  • Hengyu Ren,
  • Cong Lin,
  • Haocong Yi,
  • Shengyu Wu,
  • Xiaohu Wang,
  • Jun Wang,
  • Bin Fei,
  • Muyu Zhang,
  • Mingwei Wang,
  • Ye Sun,
  • Guojie Chen,
  • Zhefeng Chen,
  • Weixin Chen,
  • Xiaoxu Zhao,
  • Shunning Li,
  • Dong Zhou,
  • Qinghe Zhao,
  • Feng Pan

摘要

Although the anionic activity in layered oxide positive electrodes is partially understood, the mechanism by which it induces internal crack propagation under high-voltage conditions remains unclear, severely limiting stable cycle life and available capacity. In this study, the mechanism underlying internal crack propagation is elucidated in LiCoO2 under harsh float-charge conditions at 60 °C and a potential of 4.6 V vs. Li+/Li. We reveal that sequential phase transitions from O3 to O1 and then to a cation-mixed phase during deep Li+ extraction generate significant lattice-mismatch stresses that initiate internal cracks. Crucially, the accompanying anionic activity drives the migration of the oxidized lattice On− (0 < n  <  2) towards these cracks, where it even accumulates as molecular O2 that can be released upon crack propagation to the surface. It is identified that the sustained O1tocation-mixed phase transition and the bulk lattice On− migration synergistically drive the interior crack propagation, ultimately leading to LiCoO2 disintegration and electrochemical degradation. This work not only deepens our understanding of the anionic activity in layered positive electrodes but also provides mechanistic insights for the future design of stable LiCoO2 positive electrodes.