Flexible Sulfide Electrolyte Thin Membrane with Ultrahigh Ionic Conductivity for All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) employing Li-metal anode, sulfide solid electrolyte (SE) can deliver high energy density with high safety. The thick SE separator and its low ionic conductivity are two major challenges. Herein, a 30 μm sulfide SE membrane with ultrahigh room temperature conductivity of 8.4 mS cm –1 is realized by mechanized manufacturing technologies using highly conductive Li 5.4 PS 4.4 Cl 1.6 SE powder. Moreover, a 400 nm magnetron sputtered Al 2 O 3 interlayer is introduced into the SE/Li interface to improve the anodic stability, which suppresses the short circuit in Li/Li symmetric cells. Combining these merits, ASSLBs with LiNi 0.5 Co 0.2 Mn 0.3 O 2 as the cathode exhibit a stable cyclic performance, delivering a discharge specific capacity of 135.3 mAh g –1 (1.4 mAh cm –2 ) with a retention of 80.2% after 150 cycles and an average Coulombic efficiency over 99.5%. The high ionic conductivity SE membrane and interface design principle show promising feasible strategies for practical high performance ASSLBs.