Simultaneous establishment of high conductivity and mechanical stability via pore-filling of porous PTFE substrate with poly(ethylene glycol) and ionic liquid for lithium secondary battery

Abstract

Abstract Highly ion conductive and mechanically stable solid state electrolyte (SSE) membranes were prepared by impregnation of porous poly(tetrafluoroethylene) (PTFE) substrate with poly(ethylene glycol) (PEG), lithium bis(trifluoromethane sulfonyl)imide (Li-TFSI), and 1-butyl-1-methylpyrrollidum bis(fluoromethane sulfonyl) (PYR14-TFSI) for a lithium ion battery application. Lithium ion conductivity, interfacial resistance, thermal, mechanical and dimensional stability were examined along with the morphology. The prepared membranes showed not only the excellent tensile strength of 76.21\xa0MPa and elongation at break of 123% but also the dimensional stability up to 120\xa0°C and the thermal degradation temperature over 300\xa0°C. As the lithium ionic conductivity increased with PYR14-TFSI contents, the membrane containing 70\xa0wt% PYR14-TFSI exhibited the highest conductivity of 5.18ⅹ10−4\xa0S\xa0cm−1 at room temperature without any mechanical failure. The LiCoO2/SSE/Li cell assemblies fabricated from this membrane were capable of delivering 126.4 mAh g−1 at a low C-rate.