*2.5. Supercapacitor Assembly*

A T Swagelok-type cell assembly (BOLA Cell made from Teflon, BOLA GmbH, Grünsfeld, Germany) with a silver quasi-reference electrode disk and stainless-steel current collectors was used. Cells were assembled in a dry box (Labmaster 130, H2O, and O2 <0.1 ppm MBraun, Garching, Germany). The separator (12 mm diameter) and the electrodes (9 mm diameter) were soaked under vacuum together with the IL before the assembly. The ratio of the positive to negative electrode composite loading was >1 to achieve cell voltages higher than 3 V [32]. EDLCs were assembled with two carbon based composite electrodes alienated by a circular sheet of electrospun pullulan separator, with 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl) imide IL (EmimTFSI) as the electrolyte, as described in Figure S1b.
