Impact of Chemical Follow-up Reactions for Lithium Ion Electrolytes: Generation of Nucleophilic Species, Solid Electrolyte Interphase, and Gas Formation

• Published in: Journal of the Electrochemical Society 2017-01, Vol.164 (4), p.A684-A690
• Main Author: Burkhardt, Stephen E.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.0621704jes

In this report, calculated thermodynamic and kinetic data for ethylene carbonate reductive decompositions are presented with an emphasis on pathways ensuing from two-coordinate lithium solvation. These pathways lead to gas forming follow-up reactions and the generation of nucleophilic species. Computational methods are used to link initial solvent reduction and LiCO3- formation with follow-up chemical steps first proposed by Aurbach, leading to simultaneous formation of ethylene gas and lithium ethylene dicarbonate (LEDC). Additionally, formation of the observed poly(ethylene glycol) and poly(ethylene carbonate) oligomers can be attributed to similar routes following from alkoxide products of solvent reduction. Finally, the possible impact of these chemical steps on solvent and additive design, and cell failure mechanisms in mid- and high-voltage cells will be discussed. To the best of our knowledge, these mechanisms have not been explored previously with computational methods. Additionally, the nature of thermodynamic predictions using density functional theory lends itself to a more accurate representation of low rate solid-electrolyte interphase forming conditions. In contrast, molecular dynamics calculations of the anode interfacial (electro)chemistry often take place with little potential control resulting in high overpotentials for electron transfer.