Enabling high-performance all-solid-state lithium batteries with high ionic conductive sulfide-based composite solid electrolyte and ex-situ artificial SEI film

All-solid-state lithium batteries (ASSLBs) employing sulfide electrolyte and lithium (Li) anode have received increasing attention due to the intrinsic safety and high energy density. However, the thick electrolyte layer and lithium dendrites formed at the electrolyte/Li anode interface hinder the realization of high-performance ASSLBs . Herein, a novel membrane consisting of Li 6 PS 5 Cl (LPSCl), poly(ethylene oxide) (PEO) and Li-salt (LiTFSI) was prepared as sulfide-based composite solid electrolyte (LPSCl-PEO3-LiTFSI) (LPSCl:PEO = 97:3 wt/wt; EO:Li = 8:1 mol/mol), which delivers high ionic conductivity (1.1 × 10 −3 S cm −1 ) and wide electrochemical window (4.9 V vs. Li + /Li) at 25 °C. In addition, an ex-situ artificial solid electrolyte interphase (SEI) film enriched with LiF and Li 3 N was designed as a protective layer on Li anode (Li(SEI)) to suppress the growth of lithium dendrites. Benefiting from the synergy of sulfide-based composite solid electrolyte and ex-situ artificial SEI, cells of S-CNTs/LPSCl-PEO3-LiTFSI/Li(SEI) and Al 2 O 3 @LiNi 0.5 Co 0.3 Mn 0.2 O 2 /LPSCl-PEO3-LiTFSI/Li(SEI) are assembled and both exhibit high initial discharge capacity of 1221.1 mAh g −1 (135.8 mAh g −1 ) and enhanced cycling   stability with 81.6% capacity retention over 200 cycles at 0.05 C (89.2% over 100 cycles at 0.1 C). This work provides a new insight into the synergy of composite solid electrolyte and artificial SEI for achieving high-performance ASSLBs .