Exploring the Role of Vinylene Carbonate in the Passivation and Capacity Retention of Cu₂Sb Thin Film Anodes

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.