Tham-Additive-Induced Electric Double Layer Compression and Stabilization Enable Dendrite-Free Zinc Anodes under High Current

Abstract Aqueous zinc-ion batteries (AZIBs) are promising next-generation energy storage devices but suffer from severe dendrite growth, primarily due to uncontrolled two-dimensional (2D) diffusion of Zn2+ and sluggish desolvation kinetics, which result in short cycle life under high-rate conditions. Here, we report tris(hydroxymethyl)aminomethane (Tham) as a novel electrolyte additive that simultaneously optimizes Zn2+ diffusion and accelerates desolvation. Tham preferentially adsorbs onto the zinc surface, forming a dense protective layer that compresses the electric double layer (EDL) (d2 < d1) and reconstructs the inner/outer Helmholtz planes (IHP/OHP). This adsorption reduces repulsive forces between Zn2+ ions, promotes three-dimensional (3D) diffusion, and enables uniform Zn deposition. Concurrently, Tham decreases the water coordination number in the Zn2+ solvation sheath from 5.28 to 4.81, modulates the lowest unoccupied molecular orbital (LUMO) energy, lowers the desolvation energy barrier, and effectively suppresses the hydrogen evolution reaction (HER). As a result, Zn||Zn symmetric cells achieve stable cycling for 2800 h at 1 mA cm–2 with an areal capacity of 1 mAh cm–2, Zn||Cu asymmetric cells deliver an average Coulombic efficiency of 99.83%, and Zn||NH4V4O10 full cells retain 92% of their initial capacity after 500 cycles at 1 A g–1. This straightforward strategy of EDL regulation combined with solvation sheath reconstruction significantly enhances the overall performance of AZIBs.