Angarita-Gomez Stefany, Balbuena Perla B
Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, USA.
Phys Chem Chem Phys. 2020 Sep 30;22(37):21369-21382. doi: 10.1039/d0cp03399e.
Lithium metal is among the most promising anodes for the next generation of batteries due to its high theoretical energy density and high capacity. Challenges such as extreme reactivity and lithium dendrite formation have kept lithium metal anodes away from practical applications. However, the underlying mechanisms of Li ion deposition from the electrolyte solution onto the anode surface are still poorly understood due to their inherent complexity. In this work, density functional theory calculations and thermodynamic integration via constrained molecular dynamics simulations are conducted to study the electron and ion transfer between lithium metal slab and the electrolyte in absence of an external field. We explore the effect of the solvent chemistry and structure, distance of the solvated complex from the surface, anion-cation separation, and concentration of Li-salts on the deposition of lithium ions from the electrolyte phase onto the surface. Ethylene carbonate (EC), 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), and mixtures of them are used as solvents. These species compete with the salt anion and the Li cation for electron transfer from the surface. It is found that the structure and properties of the solvation shell around the lithium cation has a great influence on the ability of the cation to diffuse as well as on its surrounding electron environment. DME molecules allow easier motion of the lithium ion compared with EC and DOL molecules. The slow growth approach allows the study of energy barriers for the ion diffusion and desolvation during the deposition pathway. This method helps elucidating the underlying mechanisms on lithium-ion deposition and provides a better understanding of the early stages of Li nucleation.
由于锂金属具有高理论能量密度和高容量，它是下一代电池最有前景的负极材料之一。然而，诸如极端反应性和锂枝晶形成等挑战使得锂金属负极无法实际应用。然而，由于其固有的复杂性，从电解质溶液到阳极表面的锂离子沉积的潜在机制仍知之甚少。在这项工作中，进行了密度泛函理论计算和通过受限分子动力学模拟的热力学积分，以研究在没有外部场的情况下锂金属平板与电解质之间的电子和离子转移。我们探讨了溶剂化学和结构、溶剂化络合物与表面的距离、阴离子 - 阳离子分离以及锂盐浓度对锂离子从电解质相沉积到表面的影响。碳酸亚乙酯（EC）、1,2 - 二甲氧基乙烷（DME）、1,3 - 二氧戊环（DOL）及其混合物用作溶剂。这些物质与盐阴离子和锂阳离子竞争从表面进行电子转移。研究发现，锂阳离子周围溶剂化壳的结构和性质对阳离子的扩散能力及其周围电子环境有很大影响。与EC和DOL分子相比，DME分子使锂离子更容易移动。缓慢增长方法允许研究沉积过程中离子扩散和去溶剂化的能垒。该方法有助于阐明锂离子沉积的潜在机制，并更好地理解锂成核的早期阶段。
