Novel Li[(CF₃SO₂)(n-C₄F₉SO₂)N]-Based Polymer Electrolytes for Solid-State Lithium Batteries with Superior Electrochemical Performance

TLDR

Solid polymer electrolytes are promising for high‑energy rechargeable lithium batteries, offering enhanced safety and design flexibility over conventional liquid electrolytes. The study reports novel perfluorinated sulfonimide salt‑based SPEs composed of Li[(CF₃SO₂)(n‑C₄F₉SO₂)N] and poly(ethylene oxide) to achieve efficient ionic conductivity and high thermal stability for Li batteries. The authors synthesized LiTNFSI/PEO SPEs and characterized their ionic conductivity, thermal stability, interfacial impedance, and electrode morphology using electrochemical impedance spectroscopy and scanning electron microscopy. LiTNFSI‑based SPEs show excellent interfacial compatibility with Li‑metal, LiFePO₄, and sulfur cathodes, delivering over 300 cycles at 1C for Li|LiFePO₄ and over 500 cycles at 0.5C for Li‑S cells, outperforming conventional LiTFSI‑based SPEs and indicating their potential for high‑energy solid‑state Li batteries.

Abstract

Solid polymer electrolytes (SPEs) would be promising candidates for application in high-energy rechargeable lithium (Li) batteries to replace the conventional organic liquid electrolytes, in terms of the enhanced safety and excellent design flexibility. Herein, we first report novel perfluorinated sulfonimide salt-based SPEs, composed of lithium (trifluoromethanesulfonyl)(n-nonafluorobutanesulfonyl)imide (Li[(CF3SO2)(n-C4F9SO2)N], LiTNFSI) and poly(ethylene oxide) (PEO), which exhibit relatively efficient ionic conductivity (e.g., 1.04 × 10-4 S cm-1 at 60 °C and 3.69 × 10-4 S cm-1 at 90 °C) and enough thermal stability (>350 °C), for rechargeable Li batteries. More importantly, the LiTNFSI-based SPEs could not only deliver the excellent interfacial compatibility with electrodes (e.g., Li-metal anode, LiFePO4 and sulfur composite cathodes), but also afford good cycling performances for the Li|LiFePO4 (>300 cycles at 1C) and Li-S cells (>500 cycles at 0.5C), in comparison with the conventional LiTFSI (Li[(CF3SO2)2N])-based SPEs. The interfacial impedance and morphology of the cycled Li-metal electrodes are also comparatively analyzed by electrochemical impedance spectra and scanning electron microscopy, respectively. These indicate that the LiTNFSI-based SPEs would be potential alternatives for application in high-energy solid-state Li batteries.