Morphology optimizing of polyvinylidene fluoride (PVDF) nanofiber separator for safe lithium‐ion battery

Commercial polyolefin separator cannot guarantee the safety of lithium‐ion batteries at high temperatures due to their poor thermal stability. All kinds of nanofiber membranes with high thermal stability become the focus. In this paper, we have prepared PVDF nanofiber membrane by electrospinning method and have studied the relationship between the electrochemical performance and nanofiber morphology in detail. It is found that the morphology of PVDF is transformed from ball‐like to various nanofiber with increasing the concentration of spinning solution. As a result, the PVDF nanofiber membrane (24 wt%‐HP) prepared from spinning solution with the concentration of 24 wt% is composed of coarse nanofiber and fine nanofiber, which exhibits better electrochemical properties, such as cycling stability (300 cycles) and ionic conductivity (1.65 mS cm−1). LiCoO2/Li cells based on PVDF nanofiber separators have higher discharge capacity even at the current density of 5 C‐rate, superior than the cells based on PE separator. It is inspiring for high‐energy‐density battery safety to use this PVDF nanofiber separator. Use electrospinning to prepare PVDF nanofiber membrane with special structure to improve ion conductivity and cycle performance.