了解 LiNiO2 阴极表面降解的开始,ACS Applied Energy Materials

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了解 LiNiO2 阴极表面降解的开始
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2022-05-02 , DOI: 10.1021/acsaem.2c00012
Xinhao Li _{1,

2} , Qian Wang ₁ , Haoyue Guo ₁ , Nongnuch Artrith _{1,

3,

4} , Alexander Urban _{1,

2,

3}

Affiliation

镍基层状氧化物为开发用于锂离子电池的高能量无钴正极提供了一个有吸引力的平台，但在电化学循环过程中会因氧气释放而降解。虽然以前通过实验从现象学上对这种降解进行了表征，但一直缺乏对阴极表面发生的反应的原子级理解。在这里，我们开发了一种第一性原理方法，用于预测嵌入电极颗粒的表面重建作为温度和充电状态的函数。我们报告了 LiNiO _{2的表面相图}(001) 和 (104) 表面并识别在第一次充电和放电期间可能访问的表面结构。我们的计算表明，在第一次充电期间，两个表面都会经历氧气损失，从而导致表面结构发生不可逆的变化。在充电结束时，表面Ni原子迁移到四面体位点，在放电过程中它们进一步迁移到Li空位中，导致Li/Ni混合放电表面相。此外，讨论了循环期间温度和电压范围对充电/放电机制的影响。因此，本研究提供了对阴极表面降解初始阶段的深入了解，并为计算设计对氧释放稳定的阴极材料奠定了基础。

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Understanding the Onset of Surface Degradation in LiNiO2 Cathodes

Nickel-based layered oxides offer an attractive platform for the development of energy-dense cobalt-free cathodes for lithium-ion batteries but suffer from degradation via oxygen gas release during electrochemical cycling. While such degradation has previously been characterized phenomenologically with experiments, an atomic-scale understanding of the reactions that take place at the cathode surface has been lacking. Here, we develop a first-principles methodology for the prediction of the surface reconstructions of intercalation electrode particles as a function of the temperature and state of charge. We report the surface phase diagrams of the LiNiO₂ (001) and (104) surfaces and identify surface structures that are likely visited during the first charge and discharge. Our calculations indicate that both surfaces experience oxygen loss during the first charge, resulting in irreversible changes to the surface structures. At the end of charge, the surface Ni atoms migrate into tetrahedral sites, from which they further migrate into Li vacancies during discharge, leading to Li/Ni mixed discharged surface phases. Further, the impact of the temperature and voltage range during cycling on the charge/discharge mechanism is discussed. The present study thus provides insight into the initial stages of cathode surface degradation and lays the foundation for the computational design of cathode materials that are stable against oxygen release.

更新日期：2022-05-02

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