The cycling performance of Si-nanoparticle/Li cells with different electrolytes has been investigated. Cells containing standard binary LiPF6/ethylene carbonate/ethyl methyl carbonate electrolytes have poor capacity retention (46 %) after 50 cycles. Cells cycled with fluoroethylene carbonate (FEC)-based electrolyte have much better capacity retention (74 %). The effect of incorporation of flame-retardant co-solvents triphenyl phosphate and dimethyl methylphosphonate was investigated with both the standard and FEC electrolytes. The incorporation of the FR co-solvents did not significantly alter the performance of either electrolyte. Ex situ analysis via scanning electron microscopy, attenuated total reflectance infrared spectroscopy, and X-ray photoelectron spectroscopy was conducted to gain a better understanding of the role of electrolyte in solid electrolyte interphase structure and stability.