Advanced Design Strategies for Stable Sodium Metal Anodes: A Review

Sodium metal anodes (SMAs) are regarded as the most promising anode materials for next-generation high-energy-density sodium metal batteries, owing to their ultrahigh theoretical specific capacity (1166 mAh g^-1) and low electrochemical potential (-2.71 V vs. SHEs). However, their practical application is severely hindered by a series of interrelated challenges, including unstable solid electrolyte interphase (SEI) films, severe volume fluctuations arising from their hostless nature, uncontrollable dendrite growth, and the consequent low Coulombic efficiency and short cycle life. This review systematically summarizes recent progress in stabilizing SMAs through three major categories of strategies: current collector engineering, which involves the design of planar, three-dimensional, and gradient architectures to regulate the local current density and Na⁺ flux, thereby guiding uniform nucleation and enabling "bottom-up" dendrite-free deposition; electrolyte engineering, which focuses on optimizing solvents, salts, and functional additives to tailor the solvation structure, construct robust inorganic-rich SEI layers, and utilize electrostatic shielding effects to suppress dendrite formation; and artificial SEI engineering, which aims to pre-construct inorganic or inorganic-organic hybrid protective layers that establish a physicochemical barrier between the electrode and electrolyte, combining high ionic conductivity, superior mechanical strength, and sufficient flexibility. Finally, we provide a critical perspective on the remaining challenges and outline future research directions, emphasizing the importance of in situ/operando characterization, synergistic multi-strategy integration, breakthroughs in high areal capacity and high-rate performance, and artificial intelligence-driven material discovery for the practical implementation of SMAs.