Phenolphthalein-based polyether sulfone separator with multi-carbonyl induced uniform lithium deposition for high-performance lithium metal batteries

High reactivity and dendrite issue of lithium anodes hinder the development of lithium metal batteries (LMBs). However, commercial polyolefin separators may accelerate Li dendrite growth due to insufficient electrolyte affinity and lack of ion transport induction. Herein, two novel phenolphthalein-based polyether sulfone (PES-C) separators with “multi-carbonyl sites” named as PES2K-C and PES4K-C, are designed to build Li + transport channel to achieve faster Li + transport and homogeneous Li deposition behavior. The separators are realized by a simple non-solvent induced phase separation method and exhibit excellent electrolyte storage capacity and permeability, which are attributed to the high porosity and interpenetrating pore structure. Meanwhile, the carbonyl groups as anchoring sites provide so high electronegativity for separators that effectively immobilize the anion in the ion channel and accelerate Li + desolvation. Due to the gelation of electrolyte within separator, PES2K-C deliver a high ionic conductivity (1.35 mS cm −1 ) and Li + transference number (0.79) for batteries, much higher than the polyolefin separator. This optimized Li transfer behavior effectively inhibits the growth of lithium dendrites, resulting in an extremely stable Li plating/stripping cycle capability over 2000 h. With satisfactory electrochemical properties and excellent Li + transport characteristics, this strategy is feasible to prepare advanced separator for high-performance LMBs.