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arXiv 1210.1995cond-mat.mtrl-sci
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利用原子层沉积阻止锂离子电池中溶剂分解的第一性原理建模与实验研究

Using atomic layer deposition to hinder solvent decomposition in lithium ion batteries: first principles modeling and experimental studies

Kevin Leung, Yue Qi, Kevin R. Zavadil, Yoon Seok Jung, Anne C. Dillon, Andrew S. Cavanagh, Se-Hee Lee, Steven M. George

摘要:

钝化锂离子电池电极表面以防止电解质分解对于电池操作至关重要。最近关于阳极和阴极的共形原子层沉积(ALD)涂层的工作已经显示出显著的技术前景。ALD还提供了良好表征的模型平台,用于理解由电子隧穿通过钝化层引发的电解质分解。第一性原理计算揭示了两种制度的电子转移到吸附的碳酸亚乙酯分子(EC,商业电解质的主要成分)取决于电极是否是氧化铝涂层。在裸露的锂金属电极表面上,EC接受电子并在皮秒内分解。相比之下,在超高真空设置的约束密度泛函理论计算表明,与氧化物涂层,电子隧穿吸附EC属于非绝热制度。在这里,在谐波近似下计算的分子重组能在减慢电子转移中起着关键作用。从头算分子动力学模拟进行的液体EC-电极界面是一致的,认为反应和电子转移发生在界面上。微重力测量表明,ALD涂层降低电解质分解,并证实了理论预测。

英文摘要:

Passivating lithium ion battery electrode surfaces to prevent electrolyte decomposition is critical for battery operations. Recent work on conformal atomic layer deposition (ALD) coating of anodes and cathodes has shown significant technological promise. ALD further provides well-characterized model platforms for understanding electrolyte decomposition initiated by electron tunneling through a passivating layer. First principles calculations reveal two regimes of electron transfer to adsorbed ethylene carbonate molecules (EC, a main component of commercial electrolyte) depending on whether the electrode is alumina-coated. On bare Li metal electrode surfaces, EC accepts electrons and decomposes within picoseconds. In contrast, constrained density functional theory calculations in an ultra-high vacuum setting show that, with the oxide coating, e- tunneling to the adsorbed EC falls within the non-adiabatic regime. Here the molecular reorganization energy, computed in the harmonic approximation, plays a key role in slowing down electron transfer. Ab initio molecular dynamics simulations conducted at liquid EC-electrode interfaces are consistent with the view that reactions and electron transfer occur right at the interface. Microgravimetric measurements demonstrate that the ALD coating decreases electrolyte decomposition and corroborate the theoretical predictions.

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