A Janus separator based on Cu1Ag single-atom alloy and CeO2 with frustrated Lewis pairs for advanced Zn-I2 batteries

Aqueous zinc-iodine (Zn-I 2 ) batteries hold promise for grid-scale energy storage but face challenges from polyiodide shuttling at the cathode and dendrite growth at the anode. In this work, we rationally develop a novel Janus separator (Cu 1 Ag SAA@GF@FLPs-CeO 2 ) via plasma magnetron sputtering to tackle the issues at both cathode and anode synchronously. The anode-facing side with a silver-copper single-atom alloy (Cu 1 Ag SAA) layer can homogenize Zn 2+ flux, lower nucleation barriers, and enable dendrite-free Zn deposition, achieving 2000 ​h of exceptional stability in Zn||Zn symmetric cells at a high current density of 30 ​mA ​cm -2 . The cathode-facing side decorated with oxygen vacancy-enriched CeO 2 can effectively chemisorb polyiodide ions and accelerate the catalytic conversion of I 3 - to I - through the frustrated Lewis pairs. This bi-directional separator design ensures an ultralong stability of the Zn-I 2 batteries over 60 000 cycles at 10 ​A ​g -1 , with a high capacity retention of 94.3%. Multi-scale characterizations and theoretical calculations reveal that the spatially resolved interfacial chemistry regulates both the Zn 2+ deposition kinetics and I 3 - conversion pathway.