Bulk-to-IHP Zn Interphase Engineering With Mannitol Additive Enables (002)-Textured Zn Plating With Suppressed Hydrogen Evolution Reaction for Ah-Level Aqueous Zinc-Iodine Pouch Cells.

Abstract

Aqueous zinc-iodine batteries are promising contenders for next-generation grid-scale energy storage batteries. However, their deployment is hindered by zinc anode degradation at moderate cycling rates (0.5-2 C), including dendrite growth and parasitic hydrogen evolution reaction (HER), stemming from an unstable Zn/electrolyte interphase. Herein, a sugar alcohol-based multifunctional additive of mannitol (ML), identified via theoretical screening based on molecular characteristics of electrostatic polarity, H₂O binding energy, and LUMO level, is proposed to achieve comprehensive Zn/electrolyte interphase stabilization from the bulk phase to the inner Helmholtz plane (IHP). Leveraging abundant hydroxyl groups and good Zn²⁺ affinity, ML disrupts the bulk hydrogen-bond network and reconstructs Zn²⁺ solvation structure, simultaneously suppressing proton-hopping pathways and accelerating Zn²⁺ desolvation. Moreover, robust chemisorption of ML molecules on both Zn (002) and Zn (101) planes modulates Zn deposition toward the thermodynamically stable (002) texture with enlarged grain size, thereby enabling dendrite-free plating. Benefiting from these synergistic effects, Zn||I₂ full cells achieve an ultrahigh areal capacity of 6.5 mAh cm^-2 over 3000 cycles at a practical rate of 1 C. Multiple Ah-level Zn||I₂ pouch cells are also demonstrated, sustaining 1000 cycles with only 0.02% capacity decay per cycle, underscoring strong prospects for practical large-scale application.