关于锂空气电池阴极单线态氧释放的新见解：定期 DFT 与 CASPT2 嵌入式集群计算,Journal of Chemical Theory and Computation

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关于锂空气电池阴极单线态氧释放的新见解：定期 DFT 与 CASPT2 嵌入式集群计算
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2023-07-11 , DOI: 10.1021/acs.jctc.3c00393
Francesca Fasulo ₁ , Arianna Massaro ₂ , Ana B Muñoz-García _{1,

3} , Michele Pavone _{2,

3}

Affiliation

锂空气电池是一种有前景的大规模应用储能技术，但电池运行过程中高活性单线态氧（ ¹ O _{2 ）的释放是一个主要问题，明显限制了其有效部署。}深入了解¹ O ₂形成的反应机制对于防止其与电解质物质发生有害反应至关重要。然而，描述高度相关物种（例如单线态氧）的难以捉摸的化学对于基于密度泛函理论的最先进的理论工具来说是一项具有挑战性的任务。因此，在本研究中，我们应用基于CASPT2和有效点电荷的嵌入式簇方法来解决氧化过程中Li ₂ O _2表面¹ O _{2的演化，}即电池充电过程。基于最近的假设，我们描述了从 (112̅0)–Li ₂ O ₂表面终止发生的可行的 O ₂^2– /O ₂^– /O _2机制。^{我们的高精度计算允许将稳定的超氧化物识别为1} O ₂释放沿势能面 (PES) 的局部最小值，这是周期性 DFT 无法检测到的。我们发现¹ O _{2 的}释放是通过两步单电子过程中的超氧化物中间体或另一种仍可访问的具有一步双电子机制的途径进行的。在这两种情况下，它代表了电池充电时Li ₂ O ₂氧化的可行产物。^{因此，调节中间超氧化物物质的相对稳定性可以实现旨在控制1} O ₂对新型高性能锂空气电池的有害发展的关键策略。

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New Insights on Singlet Oxygen Release from Li-Air Battery Cathode: Periodic DFT Versus CASPT2 Embedded Cluster Calculations

Li-air batteries are a promising energy storage technology for large-scale applications, but the release of highly reactive singlet oxygen (¹O₂) during battery operation represents a main concern that sensibly limits their effective deployment. An in-depth understanding of the reaction mechanisms underlying the ¹O₂ formation is crucial to prevent its detrimental reactions with the electrolyte species. However, describing the elusive chemistry of highly correlated species such as singlet oxygen represents a challenging task for state-of-the-art theoretical tools based on density functional theory. Thus, in this study, we apply an embedded cluster approach, based on CASPT2 and effective point charges, to address the evolution of ¹O₂ at the Li₂O₂ surface during oxidation, i.e., the battery charging process. Based on recent hypothesis, we depict a feasible O₂^2–/O₂^–/O₂ mechanisms occurring from the (112̅0)–Li₂O₂ surface termination. Our highly accurate calculations allow for the identification of a stable superoxide as local minimum along the potential energy surface (PES) for ¹O₂ release, which is not detected by periodic DFT. We find that ¹O₂ release proceeds via a superoxide intermediate in a two-step one-electron process or another still accessible pathway featuring a one-step two-electron mechanism. In both cases, it represents a feasible product of Li₂O₂ oxidation upon battery charging. Thus, tuning the relative stability of the intermediate superoxide species can enable key strategies aiming at controlling the detrimental development of ¹O₂ for new and highly performing Li-air batteries.

更新日期：2023-07-11

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