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

Abstract

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···-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 × 10−4 S cm−1 at 30 °Ϲ and a high lithium ion transference number of 0.77. When employed in assembling LiFePO4|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 μA cm−2 (35 °Ϲ).