A Systematic Comparison of 10 Known Electrolyte Additives for Silicon‐Based Anodes in Lithium‐Ion Batteries in One Setup

Electrolyte additives are widely used to improve the cycling stability of lithium‐ion batteries (LIBs) with silicon‐based anodes, yet their performance is often evaluated under nonrepresentative conditions. Here, 10 literature‐known additives were systematically investigated in identical Si/C‖LiNi _0.6 Mn _0.2 Co _0.2 O ₂ (NMC622) coin cells using LP57 (1.0 M lithium hexafluorophosphate in ethylene carbonate/ethyl methyl carbonate 3:7) as baseline electrolyte. This approach enables direct and application‐relevant comparison of cycle life, interphase resistance, and Coulombic efficiency (CE). Fluoroethylene carbonate shows the most pronounced improvement, more than doubling the state‐of‐health at 80% capacity retention (SoH80), while maintaining low overpotentials and stable CE, indicating formation of a robust solid electrolyte interphase (SEI). Vinylene carbonate, 1,3,2‐dioxathiolane‐2,2‐dioxide, and succinic anhydride provide moderate improvements, whereas ethoxysilanes mainly stabilize CE without preventing long‐term fade. Other additives show no benefit. Differential capacity analysis (dQ/dV) reveals that early additive decomposition, particularly ring‐opening reactions of cyclic compounds, correlates with improved performance. Postmortem analysis indicates surface and SEI modifications, which alone do not ensure stability. These results highlight the necessity of full‐cell testing for realistic evaluation of LIB electrolyte additives.