Examining the Solid Electrolyte Interphase on Binder-Free Graphite Electrodes

The solid electrode interphase (SEI) on graphite electrodes is important to the performance, calendar life, and safety characteristics of lithium-ion cells. This article examines the SEI formed on binder-free graphite electrodes prepared by electrophoretic deposition. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis data were obtained on electrodes cycled in cells containing four electrolytes comprising ethylene carbonate: ethylmethyl carbonate (3:7 by weight) solvent and 1.2 M LiPF6, 1 M LiF2BC2O4, 1 M LiBF4, or 0.7 M LiB(C2O4)(2) salt. Our observations suggest that, in addition to solvent reduction, the reduction of electrolyte salts plays an important role in SEI formation. Mechanisms to account for the formation of these SEI constituents are included in the article.