The search for a solid electrolyte, as a polysulfide barrier, for lithium/sulfur batteries

Abstract

Composite Li10SnP2S12 (LSPS)/polyethylene oxide (PEO) films, containing 25 to 50 % polymer, were electrophoretically deposited from acetone-based suspension and tested as possible candidates for polysulfide barriers in Li/S batteries. It was found by XRD and XPS tests that saturation of composite films by LiI salt, followed by prolonged annealing at 90 °C, diminishes the crystallinity of neat LSPS and results in the formation of a novel composite Li10+xIxSnP2S12 (LISPS)/P(EO)3/LiI solid electrolyte (x < 1). The high room-temperature ion conductivity of amorphous sulfide Li10+xIxSnP2S12 (0.1–0.3 mS cm−1) is restricted by slow ion transport via the polymer electrolyte (PE) imbedded in ceramics and grain boundaries between the PE and sulfide. Increase in polymer content and temperature improves total ion transport in the LISPS/PEO system. Conformal EPD coating of sulfur and lithium sulfide cathodes by the developed composite electrolyte increased the reversible capacity and Faradaic efficiency of the Li/S and Li/Li2S cells and enabled their operation at 60 °C.