Stable Binder Boosting Sulfide Solid Electrolyte Thin Membrane for All-Solid-State Lithium Batteries

Current inorganic solid electrolyte membranes generally suffer thick thickness of hundreds micrometers as well as low ionic conductivity, which limits the energy density and cycle life of all-solid-state lithium batteries. In this work, wet coating is employed to fabricate the Li₆PS₅Cl solid electrolyte thin membrane. The interaction among solvents containing different functional groups with the Li₆PS₅Cl electrolyte was explored. A new polymeric binder is synthesized by polymerization of dimethyl aminoethyl methacrylate (DMAEMA), polyethylene glycol diacrylate (PEGDA), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), showing excellent stability to Li₆PS₅Cl solid electrolyte particles and high tensile strength of 1.46 MPa. Thus, a 40-μm-thick freestanding Li₆PS₅Cl membrane with 90 wt% Li₆PS₅Cl content is realized through in situ photo-polymerization, possessing a relatively high room temperature ionic conductivity of 1.23 mS cm⁻¹. Moreover, the all-solid-state battery-based Li₆PS₅Cl membrane exhibits superior cycling stability after 1,000 cycles with a capacity retention of 76.92% at 0.2 C under 60 ℃. When the mass load of the active material LiCoO₂ increases to 15.2 mg cm⁻², the all-solid-state cell still delivers a high initial discharge capacity of 123.0 mAh g⁻¹ (1.87 mAh cm⁻²) with a capacity retention rate of 89.93% after 200 cycles.