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

Abstract

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_0.6Mn_0.2Co_0.2O₂ (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.