The Coulombic Efficiency Trough in Silicon Anodes for Lithium-Ion Batteries: Mechanisms, Challenges, and Stabilization Strategies

Abstract

Silicon is one of the most promising anode materials for next-generation lithium-ion batteries because of its very high theoretical capacity and natural abundance, yet its practical use is limited by severe volume expansion, structural degradation, unstable solid electrolyte interphase formation, and capacity fading. Beyond these known issues, a critical but underexplored degradation feature is the Coulombic efficiency trough, a transient but universal dip in efficiency that appears during early-to-mid cycling. This trough is generally associated with silicon volume change that generates sponge-like porous structures, repeated interfacial rupture, continued SEI renewal, and irreversible lithium loss. This review analyzes the mechanistic origin of the CE trough and highlights it as a diagnostic framework that links the fundamental cause of volume change to consequences that include new surface generation, interfacial instability, and declining lithium inventory. We also evaluate major suppression strategies, including LiF-rich SEI formation through electrolyte design, mechanically adaptive binders that accommodate expansion, and voltage window optimization to limit interfacial stress. Together these approaches reduce irreversible reactions, stabilize the SEI, and improve cycling stability. Treating the CE trough as a quantitative performance indicator provides a unified basis for comparing mitigation strategies and advancing durable, high-capacity silicon anodes.