Regulating Inorganic and Organic Components to Build Amorphous‐ZnFx Enriched Solid‐Electrolyte Interphase for Highly Reversible Zn Metal Chemistry

The introduction of inorganic crystallites into a solid-electrolyte interphase (SEI) is an effective strategy for improving the reversibility of the Zn metal anode (ZMA). However, the structure-performance relationship of the SEI is not fully understood because the existing forms of its inorganic and organic components in their pristine states are not resolved. Here, a highly effective SEI is constructed for ZMA using a bisolvent electrolyte and resolved its composition/structure by cryogenic transmission electron microscopy. This highly fluorinated SEI with amorphous inorganic ZnF_x uniformly distributed in the organic matrix is largely different from the common mosaic and multilayer SEIs with crystalline inorganics. It features improved structural integrity, mechanical toughness, and Zn²⁺ ion conductivity. Consequently, the ZMA exhibits excellent reversibility with an enhanced plating/stripping Coulombic efficiency of 99.8%. The ZMA-based full cell achieves a high Zn utilization ratio of 54% at a practical areal capacity of 3.2 mAh cm^-2 and stable cycling over 1800 h during which the accumulated capacity reached 5600 mAh cm^-2 . This research highlights the detailed structure and composition of amorphous SEIs for highly reversible metal anodes.