Kinetic Stability of Bulk LiNiO2 and Surface Degradation by Oxygen Evolution in LiNiO2‐Based Cathode Materials,Advanced Energy Materials

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Kinetic Stability of Bulk LiNiO2 and Surface Degradation by Oxygen Evolution in LiNiO2‐Based Cathode Materials
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2018-11-02 , DOI: 10.1002/aenm.201802586
Fantai Kong ₁ , Chaoping Liang ₁ , Luhua Wang ₁ , Yongping Zheng ₁ , Sahila Perananthan ₂ , Roberto C. Longo ₁ , John P. Ferraris ₂ , Moon Kim ₁ , Kyeongjae Cho _{1,

3}

Affiliation

Capacity degradation by phase changes and oxygen evolution has been the largest obstacle for the ultimate commercialization of high‐capacity LiNiO₂‐based cathode materials. The ultimate thermodynamic and kinetic reasons of these limitations are not yet systematically studied, and the fundamental mechanisms are still poorly understood. In this work, both phenomena are studied by density functional theory simulations and validation experiments. It is found that during delithiation of LiNiO₂, decreased oxygen reduction induces a strong thermodynamic driving force for oxygen evolution in bulk. However, oxygen evolution is kinetically prohibited in the bulk phase due to a large oxygen migration kinetic barrier (2.4 eV). In contrast, surface regions provide a larger space for oxygen migration leading to facile oxygen evolution. These theoretical results are validated by experimental studies, and the kinetic stability of bulk LiNiO₂ is clearly confirmed. Based on these findings, a rational design strategy for protective surface coating is proposed.

中文翻译：

LiNiO2基正极材料中块状LiNiO2的动力学稳定性和氧释放引起的表面降解

相变和氧释放引起的容量降低一直是高容量LiNiO ₂基正极材料最终商业化的最大障碍。这些局限性的最终热力学和动力学原因尚未得到系统的研究，其基本机理仍知之甚少。在这项工作中，通过密度泛函理论模拟和验证实验研究了这两种现象。发现在LiNiO ₂脱锂过程中，减少的氧还原引起大量的氧气释放的强大的热力学驱动力。但是，由于大的氧气迁移动力学势垒（2.4 eV），在本体相中从动力学上禁止了氧气的释放。相反，表面区域为氧气迁移提供了更大的空间，从而导致了容易的氧气析出。这些理论结果通过实验研究得到验证，并且清楚地证实了块状LiNiO ₂的动力学稳定性。基于这些发现，提出了一种保护性表面涂层的合理设计策略。

更新日期：2018-11-02

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