Solvated pyromellitic acid-modified separator for stable lithium metal anodes and high-performance Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries are impeded by an unstable lithium anode interface and the polysulfide shuttle effect for practical applications. To overcome these challenges, a supramolecular crystalline compound formed through hydrogen bonding between pyromellitic acid and N,N-dimethylacetamide (PMA-DMAc) is designed and utilized as a modification material for the commercial PP separator. Structural and theoretical analyses reveal that the PMA component acts as a lithiophilic anchor to preferentially capture lithium ions, while DMAc forms an ordered array of coordination centers to facilitate rapid lithium ion transport, collectively establishing a synergistic “anchoring–conduction” mechanism. For Li//Li symmetric cells, the PMA-DMAc/PP separator guides uniform lithium deposition, maintaining stable operation for over 1200 h at 5 mA cm⁻² and 1 mAh cm⁻². The PMA-DMAc supramolecular compound is effective in adsorbing polysulfides. Consequently, a Li–S cell with the PMA-DMAc/PP separator achieves a favorable specific capacity of 470 mAh g⁻¹ after 200 cycles at 5C. This work demonstrates the promise of organic-based supramolecular crystalline materials in designing multi-functional separators for Li–S batteries with high energy density.