Palygorskite‐Derived Ternary Fluoride with 2D Ion Transport Channels for Ampere Hour‐Scale Li‐S Pouch Cell with High Energy Density

Abstract Although various excellent electrocatalysts/adsorbents have made notable progress as sulfur cathode hosts on the lithium‐sulfur (Li‐S) coin‐cell level, high energy density ( W G ) of the practical Li‐S pouch cells is still limited by inefficient Li‐ion transport in the thick sulfur cathode under low electrolyte/sulfur (E/S) and negative/positive (N/P) ratios, which aggravates the shuttle effect and sluggish redox kinetics. Here a new ternary fluoride MgAlF 5 ·2H 2 O with ultrafast ion conduction–strong polysulfides capture integration is developed. MgAlF 5 ·2H 2 O has an inverse Weberite‐type crystal framework, in which the corner‐sharing [AlF 6 ]–[MgF 4 (H 2 O) 2 ] octahedra units extend to form two‐dimensional Li‐ion transport channels along the [100] and [010] directions, respectively. Applied as the cathode sulfur host, the MgAlF 5 ·2H 2 O lithiated by LiTFSI (lithium salt in Li‐S electrolyte) acts as a fast ionic conductor to ensure efficient Li‐ion transport to accelerate the redox kinetics under high S loadings and low E/S and N/P. Meanwhile, the strong polar MgAlF 5 ·2H 2 O captures polysulfides by chemisorption to suppress the shuttle effect. Therefore, a 1.97 A h‐level Li‐S pouch cell achieves a high W G of 386 Wh kg −1 . This work develops a new‐type ionic conductor, and provides unique insights and new hosts for designing practical Li‐S pouch cells.