Synergistic I₃ ^- Scavenging and Spontaneous Interphase Construction for Ultralong-Life Zinc-Iodine Batteries

Aqueous Zn-I₂ batteries combine safety, sustainability, and high theoretical capacity, making them a promising energy storage solution. However, their practical employment is impeded by challenges such as uncontrolled dendrite growth on the Zn anode, severe polyiodide shuttling effect, and the dissolution of the I₂ cathode. Herein, we propose di-tert-butyl(3-sulfonatopropyl) phosphine (DBSP) as a multifunctional electrolyte additive. DBSP mitigates HER and guides highly oriented Zn²⁺ deposition and lead to the dendrite-free (002) plane. Meanwhile, the strongly phosphine reductive center in DBSP effectively scavenges polyiodide intermediates by converting I₃ ^- into stable I^-. Notably, DBSP undergoes a spontaneous oxidative reaction with I₂, forming a robust protective interphase on the cathode that effectively suppresses I₂ dissolution. This synergistic stabilization results in exceptional electrochemical durability. Specifically, the Zn║Zn symmetric cell with the 10 DBSP electrolyte exhibits 2,300 h cycling stability at 5 mA cm^{- 2}/5 mAh cm^{- 2}. Furthermore, the Zn-I₂ full cell retains a capacity of 105.9 mAh g^-1 over 220,000 cycles at a current density of 10 A g^-1. This work establishes a new molecular-level paradigm for designing synergistic electrolyte additives and provides crucial insights for the development of durable and high-performance aqueous battery systems.