Weakening conjugation of organic cyclic additives towards advanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) offer a safe and economical option for energy storage but face zinc dendrites and parasitic reactions. Here we report 1,3,5-tris(2-hydroxyethyl) isocyanurate (THI) as an electrolyte additive that delivers environment-dependent dual-state protection for Zn anodes. In the static state, spontaneous adsorption of THI establishes an initial passivation layer on Zn, limiting direct electrolyte contact and the associated side reactions. Under an electric field, oriented water molecules weaken the conjugation effect of cyclic THI and trigger ring-opening decomposition of the adsorbed species, which generates a robust interphase with high mechanical strength and chemical stability that guides uniform Zn 2+ deposition. Meanwhile, THI reconstructs the Zn 2+ solvation shell and reduces water activity via hydrogen bonding, further suppressing hydrogen evolution reaction. Consequently, THI enables the Zn||Zn symmetric cells to operate continuously cycled for more than 5000 h at 1 mA cm −2 and 1 mAh cm −2 , representing a 30-fold extension relative to the bare ZnSO 4 electrolyte. Moreover, the Zn||NH 4 V 4 O 10 full cells retained 93.2% of their capacity after 1500 cycles at 5 A g −1 . Leveraging THI's field-activated ring-opening chemistry and dual-state protection offers a simple, low-cost route to durable AZIBs.