Protective interphases and safety enhancement in high-energy-density batteries: A critical review

High-energy-density rechargeable batteries are indispensable for electric vehicles, grid-scale energy storage, and portable electronics; however, their commercialization is constrained by interfacial instability, degradation, and safety concerns. Protective interphases, particularly the solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) where applicable, regulate ion transport, suppress parasitic reactions, and enhance electrochemical stability. Nevertheless, continuous interphase evolution, dendrite growth, electrolyte decomposition, and thermal instability remain major challenges across battery chemistries. This review primarily focuses on protective interphase engineering in conventional lithium-ion, silicon-anode lithium-ion, lithium-metal, solid-state, lithium–sulfur, and lithium–oxygen batteries, with emphasis on interphase formation, degradation mechanisms, characterization techniques, engineering strategies, and emerging data-driven approaches. Sodium-ion, zinc-ion, and multivalent batteries are additionally considered as secondary/emerging examples to demonstrate the broader applicability of interphase engineering across rechargeable battery chemistries. Recent advances in electrolyte engineering, functional additives, artificial interlayers, surface modification, and interface regulation are critically assessed. Advanced characterization techniques, multiscale computational modeling, artificial intelligence, and digital twins are further examined for understanding interfacial processes, accelerating materials discovery, and enabling predictive battery management. The analysis highlights that multifunctional, chemically stable, and mechanically robust interphases are important for suppressing degradation, improving Coulombic efficiency, enhancing cycling stability, and increasing thermal safety. Integration of operando characterization, data-driven modeling, and digital twin technologies offers promising opportunities for predictive interface design. This review provides a unified perspective on protective interphase engineering and identifies future directions toward safer, longer-lasting, and commercially viable high-energy-density rechargeable batteries.