A Janus Separator based on Cation Exchange Resin and Fe Nanoparticles‐decorated Single‐wall Carbon Nanotubes with Triply Synergistic Effects for High‐areal Capacity Zn−I2 Batteries

Zn-I2 batteries stand out in the family of aqueous Zn-metal batteries (AZMBs) due to their low-cost and immanent safety. However, Zn dendrite growth, polyiodide shuttle effect and sluggish I2 redox kinetics result in dramatically capacity decay of Zn-I2 batteries. Herein, a Janus separator composed of functional layers on anode/cathode sides is designed to resolve these issues simultaneously. The cathode layer of Fe nanoparticles-decorated single-wall carbon nanotubes can effectively anchor polyiodide and catalyze the redox kinetics of iodine species, while the anode layer of cation exchange resin rich in -SO3- groups is beneficial to attract Zn2+ ions and repel detrimental SO42- /polyiodide, improving the stability of cathode/anode interfaces synergistically. Consequently, the Janus separator endows outstanding cycling stability of symmetrical cells and high-areal-capacity Zn-I2 batteries with a lifespan over 2500 h and a high-areal capacity of 3.6 mAh cm-2 .