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

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.