Ion-dipole interactions assist small molecular additives to regulate Li⁺ coordination of poly(ethylene) oxide-based polymer electrolyte

Polymer electrolyte is an attractive material for constructing high-performance solid-state batteries. However, the overall low room-temperature ionic conductivity and low transference number impede the practical application of polymer electrolyte. Ion-dipole interaction, as non-covalent interactions, has the potential to regulate Li+ coordination. It will contribute to the selectivity filter of ion conduction and improve overall ion conduction performance. Herein, we introduced benzene sulfonamide (BS) and N-methylbenzenesulfonamide (NBS) into PEO-LiTFSI complexes, respectively. The ion-dipole interactions of Li center dot center dot center dot-N-H might be provided by the organic molecules. Due to the difference in the molecular structure between BS and NBS, the stronger ion-dipole interactions between NBS and Li+ could significantly improve the coordination of Li+. As a result, PEO-LiTFSI-NBS delivers an extraordinary ionic conductivity of 1.08 x 10(-4) S cm(-1) at 30 degrees C and a high lithium ion transference number of 0.77. When employed in assembling LiFePO4 vertical bar Li solid-state battery, the specific discharge capacity could reach 151.90 mAh g(-1) with a high coulombic efficiency of around 99.92 % at 50 mu A cm(-2) (35 degrees C).