Zheng Yu, Balbuena Perla B
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, USA.
J Chem Phys. 2021 Mar 14;154(10):104702. doi: 10.1063/5.0042896.
Localized high concentration electrolytes have been proposed as an effective route to construct stable solid-electrolyte interphase (SEI) layers near Li-metal anodes. However, there is still a limited understanding of the decomposition mechanisms of electrolyte components during SEI formation. In this work, we investigate reactivities of lithium bis(fluorosulfonyl)imide (LiFSI, salt), 1,2-dimethoxyethane (DME, solvent), and tris(2,2,2-trifluoroethyl)orthoformate (TFEO, diluent) species in DME + TFEO mixed solvents and 1M LiFSI/DME/TFEO solutions. By supplying an excess of electrons into the simulation cell, LiFSI is initially reduced via a four-electron charge transfer reaction yielding F and N(SO) . The local solvation environment has little effect on the subsequent TFEO reaction, which typically requires 6 |e| to decompose into F, HCOO, CHCF, and OCHCF. Besides, the TFEO dehydrogenation reaction mechanism under an attack of anions is also identified. Unlike salt and diluent, DME shows good stability with any excess of electrons. The energetics of most relevant reactions are characterized. Most reactions are thermodynamically favorable with low activation barriers.
局部高浓度电解质已被认为是在锂金属负极附近构建稳定的固体电解质界面（SEI）层的有效途径。然而，对于SEI形成过程中电解质成分的分解机制仍了解有限。在这项工作中，我们研究了双（氟磺酰）亚胺锂（LiFSI，盐）、1,2 - 二甲氧基乙烷（DME，溶剂）和原甲酸三（2,2,2 - 三氟乙基）酯（TFEO，稀释剂）在DME + TFEO混合溶剂和1M LiFSI/DME/TFEO溶液中的反应活性。通过向模拟电池中提供过量电子，LiFSI最初通过四电子电荷转移反应被还原，生成F和N(SO) 。局部溶剂化环境对随后的TFEO反应影响很小，TFEO通常需要6个电子分解成F、HCOO⁻、CH₂CF₃⁻和OCH₂CF₃⁻。此外，还确定了在阴离子攻击下TFEO的脱氢反应机制。与盐和稀释剂不同，DME在有任何过量电子的情况下都表现出良好的稳定性。对最相关反应的能量学进行了表征。大多数反应在热力学上是有利的，且活化能垒较低。
