Enhanced properties of solid polymer electrolytes by a bilayer nonwoven PET/nanofiber PVDF substrate for use in all-solid-state lithium metal batteries

This study reports the effects of a robust bilayer nonwoven/nanofiber fabric comprising layers of a polyethylene terephthalate (PET) microfiber with a poly(vinylidene fluoride) (PVDF) nanofiber, fabricated by an electrospinning method, as a substrate for solid polymer electrolytes (SPEs). The substrate reinforces mechanical/thermal stability and physiochemical properties (especially, ionic conductivity and electrochemical stability window) of polyethylene oxide-based SPEs, which significantly contributes to improving electrochemical performances of all-solid-state Li metal batteries (ASSLMBs). Particularly, electrochemical measurements for Li/Li symmetric and Li/LiNi0.5Mn0.3Co0.2O2 ASSLMB cells reveal that the cyclability and rate capability are largely enhanced, attributed to the suppression of Li dendrite induced short-circuit and electrochemical oxidation reactions of SPEs by the introduced substrate. These benefits result from the synergistic effects of a PET microfiber layer with superior mechanical/thermal properties and a PVDF nanofiber layer with uniform porosity and excellent electrochemical oxidative stability. As a result, this study provides a promising strategy to fabricate reliable SPEs and suggests that the robust bilayer substrate-based SPEs have great potential for application in high-performance ASSLMBs.