A 3D Hydroxylated MXene/Carbon Nanotubes Composite as a Scaffold for Dendrite-Free Sodium-Metal Electrodes.

Sodium metal is a promising anode, but uneven Na deposition with a dendrite growth seriously impedes its application. Herein, a fibrous hydroxylated MXene/carbon nanotubes (h-Ti3 C2 /CNTs) composite is designed as a scaffold for dendrite-free Na metal electrodes. This composite displays fast Na+ /electron transport kinetics and good thermal conductivity and mechanical properties. The h-Ti3 C2 contains abundant sodiophilic functional groups, which play a significant role in inducing homogeneous nucleation of Na. Meanwhile, CNTs provide high tensile strength and ease of film-forming. As a result, h-Ti3 C2 /CNTs exhibit a high average Coulombic efficiency of 99.2 % and no dendrite after 1000 cycles. The h-Ti3 C2 /CNTs/Na based symmetric cells show a long lifespan over 4000 h at 1.0 mA cm-2 with a capacity of 1.0 mAh cm-2 . Furthermore, Na-O2 batteries with a h-Ti3 C2 /CNTs/Na anode exhibit a low potential gap of 0.11 V after an initial 70 cycles.