Fadel Eric R, Faglioni Francesco, Samsonidze Georgy, Molinari Nicola, Merinov Boris V, Goddard William A, Grossman Jeffrey C, Mailoa Jonathan P, Kozinsky Boris
John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.
Robert Bosch LLC, Research and Technology Center, Cambridge, MA, 02139, USA.
Nat Commun. 2019 Jul 26;10(1):3360. doi: 10.1038/s41467-019-11317-3.
Electrochemical stability windows of electrolytes largely determine the limitations of operating regimes of lithium-ion batteries, but the degradation mechanisms are difficult to characterize and poorly understood. Using computational quantum chemistry to investigate the oxidative decomposition that govern voltage stability of multi-component organic electrolytes, we find that electrolyte decomposition is a process involving the solvent and the salt anion and requires explicit treatment of their coupling. We find that the ionization potential of the solvent-anion system is often lower than that of the isolated solvent or the anion. This mutual weakening effect is explained by the formation of the anion-solvent charge-transfer complex, which we study for 16 anion-solvent combinations. This understanding of the oxidation mechanism allows the formulation of a simple predictive model that explains experimentally observed trends in the onset voltages of degradation of electrolytes near the cathode. This model opens opportunities for rapid rational design of stable electrolytes for high-energy batteries.
电解质的电化学稳定窗口在很大程度上决定了锂离子电池的工作范围限制，但其降解机制难以表征且了解甚少。通过计算量子化学研究控制多组分有机电解质电压稳定性的氧化分解过程，我们发现电解质分解是一个涉及溶剂和盐阴离子的过程，需要对它们的耦合进行明确处理。我们发现溶剂 - 阴离子体系的电离势通常低于孤立溶剂或阴离子的电离势。这种相互削弱效应可通过阴离子 - 溶剂电荷转移络合物的形成来解释，我们对16种阴离子 - 溶剂组合进行了研究。对氧化机制的这种理解使得能够制定一个简单的预测模型，该模型可以解释在阴极附近电解质降解起始电压方面实验观察到的趋势。该模型为高能电池稳定电解质的快速合理设计提供了机会。
