Uniform nucleation of sodium in 3D carbon nanotube framework via oxygen doping for long-life and efficient Na metal anodes

The Na metal anode has long been considered as one of the most promising anode types due to its high theoretical capacity and its having the lowest electrochemical potential. Safety concerns, low efficiency, and large volume changes are severe hurdles blocking its practical application, however, especially in the case of high areal capacity. Herein, an oxygen-doped carbon nanotube framework (a-CNTs) obtained after acidification has been adopted as the Na plating matrix to regulate the homogeneous nucleation of Na metal and suppress dendrite growth. The oxygenic functional groups on the carbon nanotubes induce them "sodiophilic", which guides the homogeneous nucleation and uniform deposition of Na. In addition, the cross-conductive network and high specific surface area of a-CNTs further enhance the electrochemical performances. As a result, a-CNTs have enabled reversible plating/stripping for 1000 cycles with coulombic efficiency of 99.8% at 3 mA cm(-2) for 1 mAh cm(-2). Furthermore, the symmetrical cells could run stably for 1650 cycles at 3 mA cm(-2) for 1 mA h cm(-2), and even could run for more than 300 h at 5 mA cm(-2) at 8 mA h cm(-2), which has rarely been achieved under such aggressive working conditions.