LiZnSO4F Made in an Ionic Liquid: A Ceramic Electrolyte Composite for Solid-State Lithium Batteries

摘要

The search for good solid electrolytes constitutes a major goal towards the development of safer lithium batteries. A few candidates do exist, but they suffer either from narrow electrochemical window stability or too low ionic conductivity. Herein we report the ionic-liquid-assisted synthesis of a novel LiZnSO4F fluorosulfate phase having a sillimanite LiTiOPO4-type structure, which on simply pressed samples shows a room-temperature ionic conductivity of 10~(-5)-10~(-7) S cm~(-1)together with a 0-5 V electrochemical stability window range, while ionic-liquid-free LiZnSO4F shows an ionic conductivity four orders of magnitude lower (10~(-11)Scm~(-1)). While robustly reproducible but not yet fully understood, this finding offers new opportunities to tailor inorganic composites with higher ionic conductivity. The origin of such results is demonstrated to be rooted in a surface effect associated with the grafting of a lithium-containing ionic liquid layer. This finding opens up new opportunities for the design of ceramic composites with higher ionic conductivity and should serve as an impetus for further exploiting the chemistry of ionic liquid grafting on oxides.