Recent Advances in Electrolyte Engineering for Silicon Anodes

Silicon (Si) anodes offer ultrahigh theoretical capacity (~4200 mAh g−1) for next-generation lithium-ion batteries but suffer from severe mechanical degradation due to repetitive volume expansion (>300%). Conventional electrode-centric strategies face scalability limitations, shifting focus to electrolyte engineering as a critical solution. This review synthesizes recent advances in liquid electrolyte design for stabilizing Si anodes, emphasizing three key pillars: (i) Lithium salts that enable anion-derived inorganic-rich solid electrolyte interphase (SEI) layers with high fracture toughness; (ii) Solvent systems including carbonates, ethers, and phosphonates, where fluorination and steric hindrance tailor SEI elasticity; (iii) Functional additives (F/B/Si-containing) that form mechanically compliant interphases and scavenge detrimental species. Innovative architectures—high-concentration electrolytes (HCEs), localized HCEs (LHCEs), and weakly solvating electrolytes—are critically assessed for their ability to decouple ion transport from volume strain. The perspective highlights the imperative of hybrid solid–liquid interfaces to enable commercially viable Si anodes.