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. A Janus separator based on cation exchange resin and Fe nanoparticles‐decorated single‐wall carbon nanotubes with triple synergistic effects is exploited to suppress Zn dendrites growth, mitigate polyiodide shuttle effect and facilitate redox kinetics of iodine species. This is reflected in the outstanding cycling stability of symmetrical cells and high‐areal‐capacity Zn−I2 battery with a lifespan over 2500 h and a high‐areal capacity of 3.6 mAh cm−2.