Direct Visualization and Regulation of Interfacial Ion Concentration Layer at Zinc Metal Interfaces via an Ion-Buffering Artificial Solid Electrolyte Interphase.

Direct experimental visualization of the electrical double layer (EDL) and its associated layer formation at metal-electrolyte interfaces remains challenging yet is essential for understanding interfacial instability in zinc metal anodes. Herein, we engineer a PEO/PIM-1 hybrid polymer (PIP) as an artificial solid-electrolyte interphase (SEI) that replaces field-driven interfacial ion accumulation with confined ion buffering, thereby suppressing EDL amplification and chaotic interfacial dynamics. Liquid-phase atomic force microscopy (AFM) measurements demonstrate the elimination of voltage-dependent force amplification upon PIP modification, evidencing effective decoupling of electric-field-induced ion crowding at the Zn surface. In situ Raman spectroscopy, electrochemical analysis, and molecular dynamics simulations further reveal reduced interfacial water activity, regulated ion distribution, and homogeneous Zn stripping and deposition. PIP significantly enhances anode stability, enabling Zn|Zn symmetric cells to cycle for 2700 h and delivering a Coulombic efficiency of 98.6% in Zn|Ti cells. When coupled with I2 cathodes, PIP@Zn supports long-life 4e- Zn|I2 batteries, achieving >6000 cycles at 4 A g-1 and >27 000 cycles at 8 A g-1. For the practical application, 4e- Zn|I2 pouch cell delivers 500 mAh capacity and 500 cycles. This work offers a mechanistic framework for probing EDL dynamics and a generalizable SEI strategy for stabilizing Zn metal.