Anion‐Tailored EDL Induced Triple‐Layer SEI on High‐Capacity Anodes Enabling Fast‐Charging and Durable Sodium‐Storage

High‐capacity electrodes face a great challenge of cycling stability due to particle fragmentation induced conductive network failure and accompanied by sustained electrolyte decomposition for repeatedly build solid electrolyte interphase (SEI). Herein, Se‐solubility induced Sex2‐ as self‐adjustment electrolyte additive to regulate electric double layer (EDL) for constructing novel triple‐layer SEI (inner layer: Se; medium layer: inorganic; outer layer: organic) on high‐capacity FeS2 anode as an example for achieving stable and fast sodium storage. In detail, Sex2‐ in‐situ generated at 1.30 V (vs. Na+/Na) and was preferentially adsorbed onto EDL of anode, then converted to Se0 as inner layer of SEI. In addition, the Sex2‐ causes anion‐enhanced Na+ solvation structure could produce more inorganic (Se0, NaF) and less organic SEI components. The unique triple‐layer SEI with layer‐by‐layer dense structure alleviate the excessive electrolyte consumption with less gas evolution. As a result, the anode delivered long‐lifespan at 10 A g‐1 (383.7 mAh g‐1, 6000 cycles, 93.1%, 5 min/cycle). The Se‐induced triple‐layer SEI could be also be formed on high‐capacity SnS2 anode. This work provides a novel SEI model by anion‐tailored EDL towards stable sodium‐storage of high‐capacity anode for fast‐charging.