A binder-free CF|PANI composite electrode with excellent capacitance for asymmetric supercapacitors

In this work, carbon fiber and polyaniline (CF|PANI) composites are prepared by using an electrochemical polymerization method. The morphology and composition characterization results show that the PANI nanospheres are successfully synthesized and uniformly coated on the CF. When the electrodeposition period is 300 cycles, the as-prepared CF|PANI electrode exhibits good specific capacitance of 231.63 F/g at 1 A/g, high performance of 98.14% retention rate from 0.5 to 20 A/g, and excellent cycle stability with only 0.96% capacity loss after 1000 cycles. This is ascribed to the internal resistance that was significantly reduced without binders, which helps to the CF|PANI electrode maintains high operating potential and pseudo-capacitance performance at high current density. The symmetrical supercapacitor based on two CF|PANI electrodes connecting by acidic PVA-H2SO4 gel electrolyte exhibits an energy density of 6.55 W center dot h/kg at a power density of 564.37 W/kg. In addition, the asymmetric supercapacitor based on MoS2|MWCNTs and CF|PANI electrodes with neutral PVA-Na2SO4 gel electrolyte shows an energy density of 16.12 W center dot h/kg at a power density of 525.03 W/kg. These results indicate that the low internal resistance contributes to the high energy density of symmetrical supercapacitors and asymmetric supercapacitors at high current density and high power density, which is significant for its practical application.