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 ZnFx 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.
Keywords: amorphous SEI for Zn metal anode; cryo-TEM analysis; electrolyte engineering; organic and inorganic components in SEI; reversibility of Zn anode.
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