Oxide-Generation Reactions in Lithium-Ion Batteries: A Reaction Coordinate Analysis

In lithium-ion batteries, oligomeric species have been experimentally detected in the solid-electrolyte interphase (SEI) and are expected to form during late-stage SEI growth.^1,2 Often, the mechanisms proposed in literature posit that an oxide functional group acts as the propagator of the oligomeric growth³; however, the formation of the first oxide groups that initiate these chain reactions has been a topic of little focus. Here, we investigate various reactions (largely decarboxylation reactions) that lead to these reactive oxide groups and their associated reaction coordinates using the aimless shooting and likelihood maximization procedure.⁴ The reaction coordinates of each elementary step grant insight into the necessary chemical environment for the process to occur and allows for the comparison of interfacial (electrode-electrolyte interface) and bulk phase (liquid electrolyte) reaction mechanisms. The reaction coordinates, coupled with associated energetic profiles, allow for the estimation of the most probable sources of reactive oxide functional groups.

References:

(1) Jin, Y.; Kneusels, N. J. H.; Marbella, L. E.; Castillo-Martínez, E.; Magusin, P. C. M. M.; Weatherup, R. S.; Jónsson, E.; Liu, T.; Paul, S.; Grey, C. P. Understanding Fluoroethylene Carbonate and Vinylene Carbonate Based Electrolytes for Si Anodes in Lithium Ion Batteries with NMR Spectroscopy. J. Am. Chem. Soc. 2018, 140, 9854–9867.

(2) Jin, Y.; Kneusels, N. J. H.; Magusin, P. C. M. M.; Kim, G.; Castillo-Martínez, E.; Marbella, L. E.; Kerber, R. N.; Howe, D. J.; Paul, S.; Liu, T.; et al. Identifying the Structural Basis for the Increased Stability of the Solid Electrolyte Interphase Formed on Silicon with the Additive Fluoroethylene Carbonate. J. Am. Chem. Soc. 2017, 139, 14992–15004.

(3) Burkhardt, S. E. Impact of Chemical Follow-up Reactions for Lithium Ion Electrolytes: Generation of Nucleophilic Species, Solid Electrolyte Interphase, and Gas Formation. J. Electrochem. Soc. 2017, 164, A684–A690.

(4) Peters, B.; Trout, B. L. Obtaining Reaction Coordinates by Likelihood Maximization. J. Chem. Phys. 2006, 125.