Long-term durability and safety are required to develop Li-ion batteries that can operate at high voltages. However, side reactions, including the release of O₂ from the electrode and CO₂ from the organic electrolyte, occur at the positive-electrode/electrolyte interface during charging at high voltages. In this study, universal neural network potential (UNNP)-driven molecular dynamics (MD) calculations are used to investigate the mechanism of the reaction between Li_xCoO₂ (0 ≤ x ≤ 1) or Li_xNiO₂ (0 ≤ x ≤ 1), as the positive-electrode material, and an ethylene-carbonate-based electrolyte, with a solid–liquid interface composed of ∼1700 atoms. Molecular CO₂ and O₂ evolve from the partially or fully Li-deintercalated Li_xNiO₂, while no gas–evolution reactions are observed for Li_xCoO₂. Hence, compared Li_xNiO₂, the LiCoO₂ electrode is more stable toward the decomposition of ethylene carbonate in the charged state. The decomposition reactions at the solid–liquid interface during charging are also analyzed using a NN force field. This study provides a robust approach involving MD simulations using UNNP to better understand the side reactions in electrochemical devices, which can guide manufacturers in selecting appropriate materials.

中文翻译：

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通用神经网络 碳乙烯酯/带电电极界面处 CO2/O2 析出的势驱动分子动力学研究


开发可在高压下运行的锂离子电池需要长期的耐用性和安全性。然而，在高压充电期间，正极/电解质界面会发生副反应，包括从电极释放 O₂ 和从有机电解质中释放 CO₂。在本研究中，通用神经网络电位 （UNNP） 驱动的分子动力学 （MD） 计算用于研究作为正极材料的 Li_xCoO₂ （0 ≤ x ≤ 1） 或 Li_xNiO₂ （0 ≤ x ≤ 1） 与具有由 ∼1700 个原子组成的固液界面的乙烯-碳酸酯基电解质之间的反应机理。分子 CO₂ 和 O₂ 从部分或完全锂脱嵌的 Li_xNiO₂ 演化而来，而 Li_xCoO₂ 没有观察到析气反应。因此，与 Li_xNiO₂ 相比，LiCoO₂ 电极在带电状态下对碳酸乙烯酯的分解更稳定。还使用 NN 力场分析了充电过程中固液界面处的分解反应。本研究提供了一种强大的方法，涉及使用 UNNP 进行 MD 模拟，以更好地了解电化学器件中的副反应，从而指导制造商选择合适的材料。