Electrospun nanofiber-coated separator membranes for lithium-ion rechargeable batteries

摘要

Nanofiber-coated composite membranes were prepared by electrospinning polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-co-CTFE) and PVDF-co-CTFE/polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) onto six different Celgard? microporous battery separator membranes. Application of a PVDF-based copolymer nanofiber coating onto the surface of the battery separator membrane provides a method for improving the electrolyte absorption of the separator and the separator-electrode adhesion. Peel tests showed that both PVDF-co-CTFE and PVDF-co-CTFE/PVDF-co-HFP nanofiber coatings have comparable adhesion to the membrane substrates. Electrolyte uptake capacity was investigated by soaking the nanofiber-coated membranes in a liquid electrolyte solution. PVDF-co-CTFE and PVDF-co-CTFE/PVDF-co-HFP nanofiber-coated membranes exhibited higher electrolyte uptake capacities than uncoated membranes. It was also found that PVDF-co-CTFE nanofiber-coated membranes have higher electrolyte uptakes than PVDF-co-CTFE/PVDF-co-HFP nanofiber-coated membranes due to the smaller diameters of PVDF-co-CTFE nanofibers and higher polarity of PVDF-co-CTFE. The separator-electrode adhesion properties were also investigated. Results showed PVDF-co-CTFE and PVDF-co-CTFE/PVDF-co-HFP nanofiber coatings improved the adhesion of all six membrane substrates to the electrode.