Silicon-based negative electrodes are essential for next-generation high-capacity Li-ion batteries, with SiO₂ emerging as a promising and sustainable option. However, SiO₂ anodes have limited cycling stability, which can be improved by tailoring the solid electrolyte interphase (SEI) through electrolyte engineering. This study investigates the effects of LiPF₆ and LiFSI electrolyte salts, along with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives, on the performance of SiO₂ anodes. Galvanostatic cycling and electrochemical impedance spectroscopy (EIS) are combined with SEI composition analysis using Ar⁺-sputtered X-ray photoelectron spectroscopy and hard X-ray synchrotron photoelectron spectroscopy at different photon energies. The results show that FEC enhances capacity retention, while VC improves long-term stability at the expense of lower initial capacity. No synergistic benefits are observed from combination of both additives. LiFSI-based electrolytes deliver high initial capacities but suffer capacity fade over cycling, whereas additive-free LiPF₆ formulations lead to poor cycling stability due to the formation of a thick and resistive SEI layer. In contrast, LiFSI promotes a thinner and more inorganic-rich SEI. Both FEC and VC lead to the formation of a poly(VC) surface layer that enhances capacity retention. The FEC-derived layer, enriched with LiF and thinner in nature, exhibits improved SEI stability. These findings provide valuable insights for designing electrolytes to improve the cycling performance of SiO₂ anodes.