High performance electrospun nanofiber coated polypropylene membrane as a separator for sodium ion batteries

In most of the sodium-ion batteries (SIBs), polypropylene (PP) microporous separators are generally utilized as the separator because of their high mechanical stability and phenomenal chemical stability. However, due to the hydrophobic nature of PP, low porosity, poor wettability, and thermal stability lead to an increase in cell resistance affecting battery performance. In order to improve these characteristics, PP Celgard membranes can be coated with poly(vinylidene fluoride) (PVDF) nanofibers by utilizing electrospinning approach. Electrospinning is a unique and simple technique to produce nanofibers, which can influence porosity, electrolyte wettability, and ionic conductivity. Such a nanofiber coated Celgard membrane is studied by soaking the separator membranes with an organic liquid electrolyte solution of 1 M NaClO4 (sodium perchlorate) dissolved in ethylene carbonate (EC)/diethyl carbonate (DEC) in 1:1 by volume to form gel polymer electrolytes (GPE). The electrochemical performance of the GPE demonstrates high ionic conductivity, excellent electrolyte retention, high electrochemical stability, and good thermal stability. The half-cell, Na0.66Fe0.5Mn0.5O2/GPE/Na with nanofiber coated Celgard membrane displays high discharge capacities and excellent cycle performance compared to non-coated Celgard separator membrane.