A heatproof electrospun PES/PVDF composite membrane as an advanced separator for lithium‐ion batteries

Abstract In the present paper, the physicochemical properties of a novel composite fibrous membrane, based on a mixture of poly(aryl ether sulfone) (PES) and poly(vinylidene fluoride) (PVDF), as separators for lithium‐ion batteries are reported and discussed. Compared with the pure PVDF fibrous membrane, the introduction of PES can decrease the PVDF crystallinity while increasing the proportion of α‐phase. Meanwhile, the initial thermal decomposition temperature is enhanced by 24°C. Heat shrinkage tests and thermomechanical analyzers indicate the composite membrane has significantly improved thermal‐dimensional stability. The shrinkage rate of the composite membrane after heat‐treated at 180°C for 2 hr is only 4.8%, which is far below the Celgard separator (82%) and the pure PVDF fibrous membrane (75%). The composite membrane with excellent wettability demonstrates a high ionic conductivity (1.69 × 10 −3 S cm −1 ) at room temperature as well as high electrolyte uptake (595%). The cells assembled with the composite membrane exhibit more stable cycle performance, capacity retention, and C‐rate capability than that with polyolefin separator. These results suggest that PES/PVDF composite fibrous membrane is an effective separator for high‐performance Lithium‐ion batteries.