Electrolyte additives such as vinylene carbonate (VC) have been demonstrated to improve the capacity retention for many types of Li-ion battery electrodes, including intermetallic alloying anodes, but it is still unclear why VC extends the cycle lifetime of copper antimonide (Cu2Sb) anodes so dramatically. Here, we have studied how VC affects the solid electrolyte interface formed on Cu2Sb thin film anodes in fluorine-free electrolyte solutions in order to better understand which nonfluorinated species may play an important role in effective Cu2Sb passivation. Using differential capacity analysis and X-ray photoelectron spectroscopy, we have found that VC effectively passivates Cu2Sb and prevents Cu/Cu2Sb oxidation at high potentials. Carbonate species from the reduction of VC seem to play an important role in passivation, while inorganic species like LiClO4 from the F-free supporting electrolyte do not seem to be beneficial.