Achieving High-Performance Lithium-Sulfur Batteries by Modulating Li + Desolvation Barrier with Liquid Crystal Polymers.

Lithium-sulfur (Li-S) batteries offer high theoretical capacity but are hindered by poor rate capability and cycling stability due to sluggish Li2 S precipitation kinetics, which have been attributed to the slow conversion of polysulfide anions. Here we design and fabricate a sulfonate-group-rich liquid crystal polymer (poly-2,2'-disulfonyl-4,4'-benzidine terephthalamide, PBDT) to accelerate Li2 S precipitation by promoting the desolvation of Li+ from electrolyte. We employed commercial polypropylene (PP) separators modified by PBDT to assemble Li-S batteries, which deliver a remarkable rate capacity (761 mAh g-1 at 4 C) and cycling stability (500 cycles with an average decay rate of 0.088% per cycle at 0.5 C). A PBDT-based pouch cell even delivers an exceptional capacity of ∼1400 mAh g-1 and an areal capacity of ∼11 mAh cm-2 under lean electrolyte and high sulfur loading, demonstrating promise for practical applications. Results of Raman spectra, Molecular Dynamic (MD) and Density Functional Theory (DFT) calculations reveal that the abundant anionic sulfonate groups of PBDT aid in Li+ desolvation by attenuating Li+ -solvent interactions and lowering the desolvation energy barrier. Plus, the polysulfide adsorption/catalysis is also excluded via electrostatic repulsion. This work elucidates the critical impact of Li+ desolvation on Li-S batteries and provides a new design direction for advanced Li-S batteries. This article is protected by copyright. All rights reserved.