Nitrogen and Oxygen Co-doped Graphitized Carbon Fibers with Sodiophilic-Rich Sites Guide Uniform Sodium Nucleation for Ultrahigh-Capacity Sodium-Metal Anodes.

Sodium (Na) metal is an ideal anode for high-energy Na batteries due to the low cost and natural abundance of Na metal. Nevertheless, issues regarding dendritic and mossy Na metal deposits have prevented their practical application. Herein, nitrogen and oxygen co-doped graphitized carbon fibers (DGCF) have been developed as the Na plating hosts to direct Na metal homogeneous nucleation and suppress the growth of Na dendrites. We show experimental results as well as first-principles calculations demonstrating that the uniformly doped nitrogen and oxygen function as sodiophilic sites that direct the sodium-metal nucleation to a smooth dendrite-free anode. The resultant DGCF-Na anode can be cycled stably at 1 mA cm-2 for a high areal capacity of 12.7 mA h cm-2 with an average Coulombic efficiency of 99.8%, and a Na|Na symmetrical cell can be cycled with long-term durability for more than 1200 h at 2 mA cm-2. When coupled with P2-Na2/3Ni1/3Mn1/3Ti1/3O2 and Na3V2(PO4)3 cathodes, the DGCF-Na composite demonstrates good feasibility in full cells.