Confinement-Induced In Situ Cl^-/Cl₂ Conversion in a Cathode Enables a Lean Electrolyte Sodium-Chlorine Battery

Rechargeable metal-chlorine (Li/Na-Cl₂) batteries potentially have a high energy density, but the significant amount of electrolyte consumed to produce active metal chlorides for reversible chlorine conversion severely limits their real electrochemical performance. Herein, we use a cathode with precast metal chloride in the graphene layers as the initial active material to save the sacrificial electrolyte and deliver a fundamentally different start-up operation mode for metal-chlorine batteries. Furthermore, the metal chloride confined by the graphene layers achieves in situ confining conversion with gaseous chlorine during long cycling, causing substantially improved cathode kinetics in a lean electrolyte. With this cathode, both Li/Na-Cl₂ batteries demonstrate higher capacity and prolonged cycling performance. Typically, the obtained Na-Cl₂ batteries could deliver a high areal capacity (3 mAh cm^-2) and stable life over 300 cycles under lean electrolyte conditions (20-60 μL). This work demonstrates the practical significance of utilizing a graphene interlayer to confine metal chloride as an initial active material for rechargeable alkali-metal-Cl₂ batteries.