Uniform Lithium ion flux and robust interphase enabled by anion anchoring additive for high energy density Si-based anodes

Abstract

Silicon/graphite (Si/Gr) composite anodes offer a practical approach toward higher energy density lithium-ion batteries (LIBs), yet their performance commonly deteriorates due to interface and ionic transport driven reaction heterogeneity. Tortuous Li⁺ transport pathways induce non-uniform Li⁺ flux and localized overpotentials, which trigger spatially uneven interfacial reactions and the growth of organic-rich solid electrolyte interphase (SEI) layers with physicochemical instability. These coupled electrochemical and mechanical instabilities promote repeated SEI rupture/reformation, impedance growth, irreversible lithium loss, and electrode swelling. In this study, we report a facile electrode engineering strategy using sodium 4-vinylbenzenesulfonate as an interface stabilizing anion-anchoring additive (ISAA) for Si/Gr composite anodes. ISAA improves slurry dispersion via sulfonate-driven electrostatic stabilization, leading to a more homogeneous electrode microstructure. At the interface, anion anchoring establishes a Li⁺-enriched environment that enhances effective Li⁺ transport and homogenizes Li⁺ flux across the electrode. This regulated interfacial chemistry redirects SEI evolution toward a thin, LiF-rich inorganic interphase with superior physicochemical robustness, thereby suppressing interfacial degradation and mitigating irreversible swelling. Consequently, Si/Gr-ISAA anodes exhibit outstanding electrochemical performance in both half-cells and practical full-cell configurations. This study provides a practical approach for the development of high performance Si/Gr composite anodes for next-generation LIB.