Kuai Dacheng, Balbuena Perla B
Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, United States.
ACS Appl Mater Interfaces. 2022 Jan 19;14(2):2817-2824. doi: 10.1021/acsami.1c20487. Epub 2022 Jan 7.
The products of solvent polymerization and degradation are crucial components of the Li-metal battery solid-electrolyte interphase. However, in-depth mechanistic studies of these reactions are still scarce. Here, we model the polymerization of common lithium battery electrolyte solvents─ethylene carbonate (EC) and vinylene carbonate (VC)─near the anode surface. Being consistent with the molecular calculation, molecular dynamic (AIMD) simulations reveal fast solvent decompositions upon contact with the Li anode. Additionally, we assessed the thermochemical impacts of decarboxylation reactions as well as the lithium bonding with reaction intermediates. In both EC and VC polymerization pathways, lithium bonding demonstrated profound catalytic effects while different degrees of decarboxylation were observed. The VC polymerization pathways with and without ring-opening events were evaluated systematically, and the latter one which leads to poly(VC) formation was proven to dominate the oligomerization process. Both the decomposition and polymerization reactivities of VC are found to be higher than EC, while the cross-coupling between EC and VC has an even lower-energy barrier. These findings are in good agreement with experimental evidence and explanatory toward the enhanced performance of VC-added lithium-metal batteries.
溶剂聚合和降解产物是锂金属电池固体电解质界面的关键组成部分。然而，对这些反应的深入机理研究仍然匮乏。在此，我们对阳极表面附近常见锂电池电解质溶剂——碳酸亚乙酯（EC）和碳酸亚乙烯酯（VC）——的聚合反应进行建模。与分子计算结果一致，分子动力学（AIMD）模拟显示溶剂与锂阳极接触后会快速分解。此外，我们评估了脱羧反应的热化学影响以及锂与反应中间体的键合作用。在EC和VC的聚合途径中，锂键合均表现出显著的催化作用，同时观察到不同程度的脱羧反应。我们系统地评估了有开环和无开环事件的VC聚合途径，结果表明导致聚（VC）形成的后一种途径主导了低聚过程。研究发现，VC的分解和聚合反应活性均高于EC，而EC与VC之间的交叉偶联具有更低的能垒。这些发现与实验证据高度吻合，并且对添加VC的锂金属电池性能增强具有解释作用。
