Cyclic Carbonate Additives Effect on the Solid Electrolyte Interphase of Li Ion Batteries

We report on the effect of vinylene carbonate (VC) and vinyl ethylene carbonate (VEC) electrolyte additives on the formation, stability and Li⁺ transport properties of solid electrolyte interphase (SEI). The SEI is thought to consist of an inner inorganic part with an outer organic layer, likely formed via oligomerization of the solvent, which may change in the presence of additives.

Our analysis of a Au model anode system in a 1 M LiClO₄/propylene carbonate electrolyte solution with and without additive molecules shows that additives influence the lithiation current, as well as the mass and rigidity of the SEI film. Addition of the additive molecules increases the lithiation current. VC-containing solutions exhibit the highest lithiation currents. Interestingly, when comparing the additive containing electrolytes, increasing the concentration of additives causes an over-potential for the lithiation, which results in lower lithiation currents. These preventive effects are more pronounced in VEC containing electrolytes. Our results suggest that addition of additive molecules, influences the performance of Li ion batteries in part by modifying the SEI rigidity. Addition of VC decreases film rigidity, while providing a stable protective layer, which improves stability of the SEI film.