Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium‐Ion Batteries

Abstract

Abstract Li 7 La 3 Zr 2 O 12 ‐based Li‐rich garnets react with water and carbon dioxide in air to form a Li‐ion insulating Li 2 CO 3 layer on the surface of the garnet particles, which results in a large interfacial resistance for Li‐ion transfer. Here, we introduce LiF to garnet Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT‐2 wt % LiF (LLZT‐2LiF) has less Li 2 CO 3 on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic‐liquid electrolytes. An all‐solid‐state Li/polymer/LLZT‐2LiF/LiFePO 4 battery has a high Coulombic efficiency and long cycle life; a Li‐S cell with the LLZT‐2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li‐metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.