Impact of binder concentration and pressure on performance of symmetric CNFs based supercapacitors

This paper discussed in details the impact of binder polyvynilidene fluoride (PVDF) concentrations (5, 10 and 20 wt%) and pressures (∼382 ∼ 891 ∼ 1783 and ∼2547 MPa) for the fabrication of electrodes based on Carbon nanofibers (CNFs) for supercapcitors. The surface area, pore size distribution and morphology were characterized by Brunauer-Emmett-Teller (BET) method and SEM. The decrease in specific surface area was about 31% and pore volume 14.6% with increase in PVDF concentration from 5 to 20 wt% at ∼891 MPa pressure. The assembled electrodes were tested with two electrode system in aqueous electrolyte. The specific capacitance was 80 F/g for lowest concentration of PVDF (5 wt%) and decreased about 28.3% with increase concentrations at same pressure ∼891 MPa. In comparing the effect of pressure on specific capacitance, it increases about 38% for (PVDF, 10 wt%; pressure ∼1783 MPa) from (PVDF, 10 wt%; pressure ∼891 MPa); their corresponding power density 24502 W/kg at energy density of 6.8 Wh/Kg and 19886 W/kg at energy density energy of 3.8 Wh/kg. ESR values increase from 0.3 to 1.9 Ω with increase in PVDF concentration and decrease again to 0.5 Ω with increase in pressure. The results show optimal conditions are 10 wt% of PVDF and higher pressure of ∼891 MPa.