Interface engineering in sodium metal anodes: challenges, design strategies and perspectives

Abstract Sodium metal anodes (SMAs) possess a high theoretical capacity (1166 mAh g⁻¹), a low redox potential (−2.71 V vs. SHE), and abundant sodium resources, making sodium metal batteries (SMBs) highly promising next-generation energy storage systems. However, their practical applications remain severely constrained by instability at the electrode–electrolyte interface, leading to persistent side reactions, sodium dendrite growth, low coulombic efficiency, and a decline in cycle life. These issues are all closely related to the formation, evolution, and failure of the solid electrolyte interphase (SEI). This paper constructs an analytical framework for the interfacial chemistry of SMBs centered on the dynamic evolution of the SEI. It systematically elucidates the mechanisms of SEI formation, evolution, and failure, further systematizing interface regulation strategies in both liquid and solid electrolyte systems, with a particular focus on the fundamental differences between liquid and solid interfaces in terms of formation mechanisms, failure behavior and regulation principles. Building on this, strategies for constructing high-energy-density SMAs are discussed from the perspective of interface–structure synergistic design. Finally, in light of the key challenges currently facing research in this field, future directions are outlined, including the mechanisms of dynamic SEI evolution, descriptor-guided interface design, the chemical–mechanical coupling at solid-state interfaces, and evaluation systems tailored to real-world operating conditions. This review aims to deepen the understanding of interfacial chemistry in SMBs and to provide a theoretical basis and design guidance for the rational design and practical development of high-safety, long-lifespan SMBs.