Toward Understanding the Effect of Fluoride Ions on the Solvation Structure in Lithium Metal Batteries: Insights from First-Principles Simulations,ACS Applied Materials & Interfaces

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Toward Understanding the Effect of Fluoride Ions on the Solvation Structure in Lithium Metal Batteries: Insights from First-Principles Simulations
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2022-10-19 , DOI: 10.1021/acsami.2c14770
Jianhui Zheng ₁ , Yao Wang ₁ , Juncheng Wang ₁ , Huadong Yuan ₁ , Yujing Liu ₁ , Tiefeng Liu ₁ , Jianmin Luo ₁ , Jianwei Nai ₁ , Xinyong Tao ₁

Affiliation

Regulating the structure and composition of the lithium-ion (Li⁺) solvation shell is crucial to the performance of lithium metal batteries. The introduction of fluorine anions (F^–) into the electrolyte significantly enhances the cycle efficiency and the interfacial stability of lithium metal anodes. However, the effect of dissolved F^– on the solvation shell is rarely touched in the literature. Herein, we investigate the evolution processing of the fluorine-containing solvation structure to explore the underlying mechanisms via first-principles calculations. The additive F^– is found to invade the first solvation shell and strongly coordinate with Li⁺, liberating the bis(trifluoromethanesulfonyl) imide anion (TFSI^–) from the Li⁺ local environment, which enhances the Li⁺ diffusivity by altering the transport mode. Moreover, the fluorine-containing Li⁺ solvation shell exhibits a higher lowest unoccupied molecular orbital energy level than that of the solvation sheath without F^– additives, suggesting the reduction stability of the electrolyte. Furthermore, the Gibbs free energy calculations for Li⁺ desolvation reveal that the energy barrier of the Li⁺ desolvation process will be reduced because of the presence of F^–. Our work provides new insights into the mechanisms of electrolyte fluorinated strategies and leads to the rational design of high-performance lithium metal batteries.

中文翻译：

了解氟离子对锂金属电池溶剂化结构的影响：第一性原理模拟的见解

^{调节锂离子 (Li +} ) 溶剂化壳的结构和组成对锂金属电池的性能至关重要。在电解质中引入氟阴离子（F- ^）显着提高了锂金属负极的循环效率和界面稳定性。然而，文献中很少提及溶解的 F ^-对溶剂化壳的影响。在此，我们研究了含氟溶剂化结构的演化过程，以通过第一性原理计算探索其潜在机制。发现添加剂 F ^-侵入第一个溶剂化壳层并与 Li ^+强配位，从Li ⁺局部环境中释放双（三氟甲磺酰基）酰亚胺阴离子（TFSI ^- ），通过改变传输模式来增强Li ^{+扩散率。}此外，含氟Li ⁺溶剂化壳层的最低未占分子轨道能级比没有F ^-添加剂的溶剂化壳层更高，表明电解质的还原稳定性。^{此外，Li +}去溶剂化的 Gibbs 自由能计算表明，^由于F ^-. 我们的工作为电解质氟化策略的机制提供了新的见解，并导致了高性能锂金属电池的合理设计。

更新日期：2022-10-19

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