Cation adsorption engineering enables dual stabilizations for fast-charging Zn-I${}_2$ batteries

Aqueous zinc-iodine (Zn-I${}_2$) battery is a promising energy storage system due to its inherent safety, high theoretical capacity, sustainability, and cost-effectiveness. However, the shuttle effect of polyiodide severely affects the stable loading of active iodine and even accelerates the corrosion of the Zn anode, thus impeding its further advancement. Herein, a unique trimethylsulfonium cation (TMS${}^{+}$) with strong adsorption is proposed to stabilize both the iodine cathode and Zn anode. Benefiting from the robust interaction between TMS${}^{+}$ and polyiodide, the electrolyte can effectively immobilize large-capacity iodine in the form of oily precipitate, thus avoiding the shuttle effect of polyiodide and the Zn corrosion. Additionally, TMS${}^{+}$ can be preferentially adsorbed on various Zn facets, inducing an electrostatic shielding effect to inhibit Zn dendrite growth. Consequently, Zn anode can be stably cycled over 3400 h at 5 mA cm${}^{-2}$/5 mAh cm${}^{-2}$, and a large areal capacity of 2.71 mAh cm${}^{-2}$ as well as long-life stability over 6400 cycles is achieved for Zn-I${}_2$ battery. Furthermore, cation adsorption engineering is practically utilized in pouch cells, realizing superior fast-charging stability over 790 cycles. This electrolyte modification with dual stabilizations is anticipated to be applied to other metal-iodine batteries as a cost-effective, facile, and safe strategy. (© 2024 Wiley‐VCH GmbH)