The Mechanism of SEI Formation on Single Crystal Si(100), Si(110) and Si(111) Electrodes

Subsequent to our previous studies on the SEI formation mechanism on the single crystal silicon (100) surface, here we report on complementary studies of the SEI formation on Si surfaces with the crystal orientations (111) and (110). The differences in electrochemical behavior of the different crystal orientations are discussed - especially with regard to the effect of the SEI forming electrolyte additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) added to ethylene carbonate (EC)/diethyl carbonate (DEC) based electrolytes. Fourier transform infrared spectroscopy (FTIR) of the SEI during early stages of SEI formation and physico-chemical investigations (wetting behavior) indicate a strong dependence of the chemical composition of the SEI on the surface orientation and the electrolyte composition during the early stages of lithiation of Si. However, at a higher lithiation degree less difference in the chemical composition of the SEI can be observed. These findings are in agreement with those made for the SEI formation on the Si(100) surface.