Rationally Integrating 2D Confinement and High Sodiophilicity toward SnO2 /Ti3 C2 Tx Composites for High-Performance Sodium-Metal Anodes.

ABSTRACT

The metallic sodium (Na) is characterized by high theoretical specific capacity, low electrode potential and abundant resources, and its advantages manifests itself as a promising candidate anode of sodium metal batteries (SMBs). However, the vaporization during the plating/stripping or uncontrolled growth of sodium dendrites in sodium metal anodes (SMAs) has posed major challenges to its practical applications. To address this issue, here, the SnO2 /Ti3 C2 Tx composite is rationally fabricated, in which sodiophilic SnO2 nanoparticles are in situ dispersed on the 2D Ti3 C2 Tx , providing the acceptor sites of Na+  that can control vaporization and dendrites. The SnO2 /Ti3 C2 Tx composite anode exhibits smooth and homogeneous morphology after Na-metal deposition cycles, stable Coulombic efficiency (CE) of half cells, long stable cycles of symmetric cells due to highly sodiophilic sites, and confinement effect. In addition, the full cells assembled with Na0.6 MnO2 also show excellent rate performance and cycling performance. These discoveries demonstrate the effectiveness of the acceptor sites and the confinement effect provided by the SnO2 /Ti3 C2 Tx composite, and thus provide an additional degree of freedom for designing SMBs.