ABSTRACT Aqueous zinc‐iodine (Zn‐I 2 ) batteries offer low‐cost, safe, high‐capacity storage, but are limited by uneven Zn deposition at the anode and iodine loss at the cathode from shuttle and hydrolysis effects. Here, we systematically map the dual, interface‐specific roles of choline chloride (ChCl) during cycling and show that a single additive can simultaneously build two complementary interfacial chemistries. Ch + cations preferentially accumulate at both electrodes, but with distinct outcomes: at the cathode, Ch + forms hydrophobic Ch + ‐polyiodide complexes that confine iodine species and suppress hydrolysis; at the anode, a water‐deficient interfacial layer stabilizes Zn plating, inhibiting dendrites and mitigating corrosion. In parallel, Ch + perturbs the hydrogen‐bonding network of bulk water, reshaping Zn 2+ solvation and promoting faster ion transport. Enabled by this one‐additive/two‐interface regulation, Zn‐I 2 full cells using a ZnSO 4 ‐ChCl electrolyte deliver exceptional durability, retaining >99% capacity after 20 000 cycles at 10 A g −1 and >98% after 2000 cycles even at an areal mass loading of 24.2 mg cm −2 . Consistently, Zn||Zn symmetric cells sustain stable plating/stripping for ninefold longer than the baseline electrolyte. This work establishes a mechanistic framework for electrolyte additives that intentionally engineer both electrodes, emphasizing interfacial chemistry as a key factor for durable Zn‐I 2 batteries.
Bi et al. (Tue,) studied this question.