The use of a wide variety of NMR spectroscopy techniques to characterise the SEI that is formed on silicon on cycling will be described. We have synthesized ¹³C enriched forms of additives such as FEC, which have allowed detailed structural studies to be performed. The results have been compared to the species identified in prior work on products formed on reducing FEC with lithium naphthalenide.¹ Dynamic nuclear polarization approaches allow two dimensional experiments to be performed in reasonable timeframes helping to assign the different species observed in the ¹³C and ¹H NMR spectroscopy. Studies of coated silicon samples will be presented.

1. Michan, A. L.; Parimalam, B. S.; Leskes, M.; Kerber, R. N.; Yoon, T.; Grey, C. P.; Lucht, B. L. “Fluoroethylene Carbonate and Vinylene Carbonate Reduction: Understanding Lithium-Ion Battery Electrolyte Additives and Solid Electrolyte Interphase Formation” Chem. Mater., 2016, 28, 8149.