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.