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.