Spatially‐Decoupled Desolvation and Sodium Deposition in a Multi‐Functional Carbon Film for Highly Reversible Sodium Metal Batteries

Abstract Sodium (Na)‐deposition is often accompanied by serious electrolyte decomposition, forming unstable solid electrolyte interphase (SEI) layers inducing dendrite growth and safety risks. While three‐dimensional carbon frameworks can regulate ion flux to mitigate dendrite formation, current designs usually lack the protective interfacial layers, triggering electrolyte parasitic reactions during Na plating. Moreover, their uniformity and excessive thickness promote top‐down Na‐deposition, which thus reduces spatial utilization, especially under high current densities and deep cycling. Herein, a thickness‐tunable (5–30 µm) multi‐functional carbon film, which seamlessly integrated a protective interfacial layer with gradient sodiophilic hosts (PL/GS‐CF), is engineered to concurrently regulate desolvation and Na‐deposition. Mechanistic studies revealed that the top protective layer, with size‐tunable micropores and large carbon interlayer space, created graded sieving pathways (DME→PF 6 − →Na + ) for the rapid step‐by‐step desolvation, spatially decoupling electrolyte decomposition from Na deposition to enable the stable SEI formation and fast Na + transfer kinetics. The host units with gradient sodiophilic/dense sites and subcritical nucleation dimensions facilitated the “bottom‐up” layer‐by‐layer Na‐plating, therefore enhancing carbon volumetric‐utilization and sodium reversibility. The PL/GS‐CF@Na symmetric cells realized a competitive‐long life of 700 h with an ultra‐high reversible volumetric capacity of 1120.4 mAh cm −3 at a depth of discharge (DOD) of 100% and a current density of 12 mA cm −2 .