Separator Materials Influence on Supercapacitors Performance in Viscous Electrolytes
The aim of this paper was to study the influence of the separator material characteristics (chemical composition, morphology, thickness, porosity) on the performance of SCs at lower temperatures and viscous electrolytes. For that two different electrolytes were used: 1 M triethylmethylammonium tetrafluoroborate solution in dimethyl carbonate, ethylene carbonate and propylene carbonate mixture (TEMABF4 + DMC:EC:PC) with 1:1:1 volume ratio and 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid. Temperature dependence study was performed with TEMABF4 + DMC:EC:PC electrolyte at the temperature range from +24 to -30 °C. To study the influence of the separator material characteristics different separator materials were used: commercially available separators prepared from cellulose (TF4425) and polypropylene (Celgard2400), and self-made separators, prepared by electrospinning method from poly(vinylidene fluoride) with different surface morphologies. Carbide-derived carbon electrodes, prepared from TiC at chlorination temperature T=950°C, were used. Our SCs were tested by cyclic voltammetry, constant power discharge and electrochemical impedance spectroscopy methods.
In given paper it will be discussed how high-frequency series resistance, phase angle, characteristic relaxation time constant and specific power values of SC depends on the separator parameters used. Also it will be shown that for the high power pulse generation systems, the properties of the separator material have to be carefully optimized and separator materials effect is highly important for the viscous electrolyte solutions based SCs and for systems working at lower temperatures.