An MXene‐Based Metal Anode with Stepped Sodiophilic Gradient Structure Enables a Large Current Density for Rechargeable Na–O₂ Batteries

Abstract The metal anode is the pivotal component for advanced sodium‐metal batteries such as Na–O₂ batteries. Designing a 3D confinement scaffold is a promising strategy for constructing dendrite‐free sodium‐metal anodes; however, cycling stability at a large current density (>10 mA cm⁻²) is still difficult to realize. Herein, the design of new lightweight and fibrous hydroxylated Ti₃C₂ (h‐Ti₃C₂) MXene based scaffolds with stepped sodiophilic gradient structure (h‐M‐SSG) is reported, and its thickness can be controlled (80−250 µm). The sodiophilic gradient structure (adjusted by h‐Ti₃C₂) can effectively induce sodium ions to preferentially deposit at the bottom of the scaffold, thus inhibiting dendrite growth. h‐M‐SSG/Na‐based symmetrical batteries exhibit a low polarization voltage and long cycling life at a high current density (40 mA cm⁻²) and a high cut‐off capacity (40 mAh cm⁻²). Moreover, a Na–O₂ battery with an h‐M‐SSG/Na anode exhibits a low potential gap of 0.137 V after 45 cycles at 1000 mA g⁻¹ and 1000 mAh g⁻¹. This deposition‐regulation strategy would inspire the design of 3D scaffolds for high‐performance sodium‐metal‐anode‐based batteries.