Preparation and properties of nanofiber-coated composite membranes as battery separators via electrospinning

An electrospun nanofiber-coated Celgard^® 2400 polypropylene microporous battery separator was prepared using polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-co-CTFE). The coating of PVDF and PVDF-co-CTFE nanofibers was carried out using single nozzle and nozzle-less electrospinning methods. The nanofiber coating prepared by the nozzle-less electrospinning method was found to have better adhesion to the microporous separator membrane than the nanofiber coating prepared by single nozzle electrospinning. The PVDF and PVDF-co-CTFE nanofiber coatings increased the electrolyte uptake capacity in a secondary lithium-ion battery, with PVDF-co-CTFE co-polymer nanofiber-coated microporous membrane showing higher electrolyte uptake capacity than PVDF homopolymer-coated microporous membrane. In addition, the PVDF and PVDF-co-CTFE nanofiber coatings improved the adhesion of the porous microporous membrane to a battery electrode. It was also found that nanofiber coatings prepared by the nozzle-less electrospinning method have better adhesion properties and higher electrolyte uptake capacity than those by single nozzle electrospinning.