Facile in Situ Synthesis of Dual-Heteroatom-Doped High-Rate Capability Carbon Anode for Rechargeable Seawater-Batteries

Heteroatom doping is useful for enhancing the electrochemical performance of sodium-based secondary battery (SBB) anodes. However, the complexity of synthesis and safety issues caused by harmful dopant precursors must be overcome. Herein, a one-step plasma-in-liquid process is adopted to synthesize N and S co-doped carbon-based anode material (NS/C) for SBBs. NS/C exhibits a large specific surface area (476.8 m2 g-1) and abundant active sites on its surface owing to its void structure. Owing to the advantages of this structure, NS/C evidently caused a co-intercalation reaction in an ether-based electrolyte while avoiding solid electrolyte interface (SEI) layer formation on the anode surface. Transmission electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and the Brunauer–Emmett–Teller method with a novel analysis method using terahertz waves are employed to prove that no SEI formed on the anode surface. When the anode is applied to a sodium-ion half-cell, NS/C exhibited a remarkable cycling life of 35,000 cycles at an ultrahigh current density of 100 A g-1 with high reversible capacity of > 72 mAh g-1. Furthermore, NS/C shows outstanding electrochemical performance for a seawater battery anode, with a cycling life of more than 1,500 at the first attempted current density of 10 A g-1.