*2.2. Preparation of the Electrospun Separator*

Electrospinning was used to prepare the non-woven separator. In particular an home-made electrospinning apparatus has been used, this consisted of a high-voltage power supply (SL 50 P 10/CE/230, Spellman, West Sussex, UK), a syringe pump (200 series, KD Scientific, Holliston, MA, USA), a glass syringe containing the polymer solution and connected to a stainless-steel blunt-ended needle (inner diameter = 0.51 mm) through a polytetrafluoroethylene (PTFE) tube. The Pu membrane was electrospun starting from a 23% *w*/*v* solution of pullulan in Milli-Q water. The solution was spun at 18 kV at 20 cm from the collector with a flow rate of 1 mL h<sup>−</sup>1. The cellulose triacetate (CTA) separator has been electrospun starting from a 6% *w*/*v*. solution in DCM/EtOH 80/20 solution. The solution was spun at 15 kV and at a 15 cm distance from the collector with a flowrate of 2 mL/h, at room temperature (RT) with a relative humidity of 40–50%. After electrospinning the mat has been soaked into a 0.1 M solution of sodium hydroxide in a mixture of Ethanol and water 4:1 *v*/*v* for 24 h. In the end the electrospun separator was washed in MilliQ water twice for fifteen minutes each.
