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

Abstract 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 Se x 2− as self‐adjustment electrolyte additive to regulate electric double layer (EDL) for constructing novel triple‐layer SEI (inner layer: Se; mediate layer: inorganic; outer layer: organic) on high‐capacity FeS 2 anode as an example for achieving stable and fast sodium storage. In detail, Se x 2− in situ generated at 1.30 V (vs. Na + /Na) and was preferentially adsorbed onto EDL of anode, then converted to Se 0 as inner layer of SEI. In addition, the Se x 2− causes anion‐enhanced Na + solvation structure could produce more inorganic (Se 0 , 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 SnS 2 anode. This work provides a novel SEI model by anion‐tailored EDL towards stable sodium‐storage of high‐capacity anode for fast‐charging.