A Biomimetic Bidirectional Interphase Enabled by a Single Molecule for Ultra-Stable Zn-I₂ Batteries

Though zinc-iodine (Zn-I₂) batteries hold considerable promise for grid-scale energy storage, their development remains constrained by zinc dendrite formation, detrimental side reactions, and polyiodide shuttle. In this work, sodium camphorsulfonate (SCS) is introduced as a biomimetic bidirectional electrolyte additive to simultaneously address these issues. At the anode, SCS participates in the Zn^{2 +} solvation to suppress HER, while its preferential adsorption on Zn anode guides the dendritefree (002) plane. At the cathode, the SCS exhibits strong binding affinity toward I₂, effectively inhibiting polyiodide shuttle. Moreover, the adsorbed SCS layer on Zn acts as a barrier against migrating polyiodides, mitigating Zn anode interfacial corrosion. Thus, the Zn||Zn symmetric cell with 10 SCS/BE demonstrates ultra-stable cycling for 1449 h at 5 mA cm^{- 2}/5 mAh cm^{- 2}. The Zn-I₂ full cell retains 154.0 mAh g^{- 1} capacity after 26 000 cycles at 5 A g^{- 1}. The corresponding pouch battery with a 20 µm Zn foil and a high iodide loading (10.5 mg cm^{- 2}) cathode displays a capacity of 175.1 mAh g^{- 1} after 500 cycles at 0.5 A g^{- 1}. This work provides a cost-effective design strategy for stabilizing both electrodes in Zn-I₂ batteries through a single molecular additive and guarantee a durable cyclic performance of Zn-I₂ batteries.