An All-Solid-State Battery Based on Sulfide and PEO Composite Electrolyte

Abstract

Replacing liquid electrolytes with solid polymer electrolytes (SPEs) is considered as a vital approach to developing sulfur (S)-based cathodes. However, the polysulfides shuttle and the growth of lithium (Li) dendrites are still the major challenges in polyethylene oxide (PEO)-based electrolyte. Here, an all-solid-state Li metal battery with flexible PEO-Li₁₀ Si_0.3 PS_6.7 Cl_1.8 (LSPSCl)-C-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) composite cathode (FCC) and PEO-LSPSCl-LiTFSI composite electrolyte (S-CPE) is designed. The initial capacity of the Li|S-CPE|FCC battery is 414 mAh g^-1 with 97.8% capacity retention after 100 cycles at 0.1 A g^-1 . Moreover, the battery displays remarkable capacity retention of 80% after 500 cycles at 0.4 A g^-1 . Cryo-transmission electron microscopy (Cryo-TEM) reveals rich large-sized Li₂ CO₃ particles at the Li/PEO interface blocking the Li⁺ transport, but the layer with rich Li₂ O nanocrystals, amorphous LiF and Li₂ S at the Li/S-CPE interface suppresses the growth of lithium dendrite and stabilizes the interface. In situ optical microscopy demonstrates that the excellent cyclic stability of FCC is ascribed to the reversible shuttle of P-S-P species, resulting from the movement of ether backbone in PEO. This study provides strategies to mitigate the polysulfide shuttle effect and Li dendrite formation in designing high energy density solid-state Li-S-based batteries.

Keywords: composite electrolyte; flexible composite cathode; growth of lithium dendrite; lithium metal battery; reversible shuttle.