Defect-rich carbon materials with abundant oxygen functional groups at edge/defect sites for rechargeable sodium-chlorine batteries.

Because of the high theoretical energy density and abundant resources, rechargeable sodium‑chlorine (NaCl2) batteries have attracted great attention as an emerging alternative and complementary for conventional energy storage systems. However, their practical application faces critical challenges, including complicated multiphase transformation, easy Cl2 escape, cathode passivation by NaCl, and commonly exhibit sluggish rate performance and poor cycling life. Herein, we demonstrate the application of one defect-rich carbon with abundant oxygen functional groups at edge/defect sites (DC-O) as an efficient cathode for rechargeable NaCl2 batteries. The defect regions surrounding the porous carbon cavities can locally enrich Na+ and predefine spatially distributed nucleation sites for NaCl formation, effectively confining the deposition of NaCl and preventing Cl2 escape. Furthermore, the polarized oxygen groups anchored on carbon defects are beneficial for the uniform dispersion of NaCl nucleation and inhibit cathode passivation. The DC-O-based battery delivered a high discharge capacity (initial 9290 mAh g-1, rechargeable 4000 mAh g-1), excellent rate performance and long cycling life (400 cycles). Even under extreme conditions, such as low temperature (-20 °C), high active material loading, and lean electrolyte amount, the battery still exhibited superior electrochemical performance. This study presents induced confinement engineering to guide novel conversion-type battery design.