Effect of emulsified polymer binders on the performance of activated carbon electrochemical double-layer capacitors

The electrochemical properties of two water-emulsified polymers, styrene-butadiene rubber, and polytetrafluoroethylene, on activated carbon electrochemical capacitors were systematically compared. All electrodes were fabricated with different ratios of styrene-butadiene rubber and polytetrafluoroethylene: 4 : 0, 3 : 1, 2 : 2, and 1 : 3. A good dispersion of styrene-butadiene rubber nanoparticles maintains mesopores in activated carbon, whereas an increase in polytetrafluoroethylene binder content in the electrodes reduces mesoporous surface area significantly due to the lump polytetrafluoroethylene structure coagulated by smashed particles in water. The relatively strong adhesion of the styrene-butadiene rubber binder also leads to better cyclability for extremely long cycles and the rate capability with various current densities at room temperature. At a high temperature of 60 °C, however, the electrodes containing polytetrafluoroethylene binder showed comparable high specific capacitance due to the high thermal stability of polytetrafluoroethylene.