Engineering fast-charging anodes for solid-state sodium batteries: Materials progress, interfacial kinetics, and emerging design strategies

The growing demand for safe, sustainable, and high-power energy storage systems has accelerated the development of sodium-based batteries as promising alternatives to conventional lithium-ion technologies. In particular, solid-state sodium batteries (Na SSBs) offer improved safety, wider electrochemical stability, and the potential for fast-charging operation. However, the anode often becomes the key kinetic and stability bottleneck due to sluggish Na + diffusion, interfacial polarization, and chemo-mechanical degradation. This review presents a comprehensive overview of recent advances in anode materials for fast-charging solid-state sodium batteries, emphasizing the fundamental mechanisms governing Na + transport, interfacial electrochemistry, and mechanical stability. The article first discusses the fundamental processes controlling charge–discharge behavior in Na SSBs. Subsequently, major classes of anode materials are systematically reviewed, including metallic sodium, alloy-type anodes (Si, Ge, Sn, Sb, Bi), carbon-based frameworks, composite architectures, and emerging high-entropy or hybrid materials. Particular attention is given to interface engineering strategies, microstructural optimization, and electrolyte compatibility that enable improved fast-charging performance and enhanced cycling stability. Finally, current challenges and future research directions are discussed, highlighting the need for integrated materials design, advanced characterization, and computational screening to accelerate the development of high-performance anodes. This review provides a mechanistic and design-oriented roadmap for engineering next-generation fast-charging solid-state sodium batteries.