Engineering Three-Dimensional Current Collectors for Stable Sodium Metal Anodes.

Sodium metal batteries have emerged as promising candidates for next-generation high-energy-density storage systems because of the abundant resources of sodium and the high theoretical capacity of sodium metal anodes (SMAs). However, the practical application of SMAs faces significant challenges, including uncontrollable dendrite growth, substantial volume changes, and unstable solid electrolyte interfaces. These issues result in a short battery cycle life and heightened safety risks. In recent years, the design of three-dimensional current collectors has been recognized as an effective strategy for addressing these challenges. This review systematically dissects the fundamental mechanisms underlying stable SMAs, focusing on the space charge effect, mass transport regulation, and nucleation thermodynamics governed by interfacial sodiophilicity. It then provides a comprehensive overview of recent advances in three-dimensional current collectors, categorizing them into carbon-based systems (e.g., heteroatom doping, 3D printing, and sodiophilic gradient design) and metal-based systems (e.g., porous/nanoengineered structures and surface modification). These designs aim to lower the local current density, create ample nucleation sites, and accommodate volume expansion, effectively suppressing dendrite growth while improving the Coulombic efficiency, cycling stability, and safety of SMAs. Finally, this review outlines future directions, providing references for the development of high-performance and practical SMAs.