Conducting polymer micro-supercapacitors for flexible energy storage and Ac line-filtering

We propose a novel surfactant-mediated process to fabricate flexible microsupercapacitors (MSCs) combining conventional photolithography and electrochemical deposition. The anionic surfactant mediates the process of electropolymerisation at a lower anodic potential while causing template effects in producing porous conducting poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes. Using this strategy, PEDOT MSCs with remarkable performance in terms of tunable frequency response and energy density are achieved. Specifically, ultrahigh scan rate capability up to 500V/s is achieved with a crossover frequency of 400Hz at a phase angle of -45°. This is the first polymer-based redox microsupercapacitor with excellent frequency characteristics other than carbonaceous-based electrochemical double layer capacitors reported so far in the literature. Thus, the micro-supercapacitors exhibit maximum areal cell capacitance of 9mF/cm2 with a volumetric stack capacitance of 50F/cm3 in 1M H2SO4 aqueous electrolyte. The flexibility and stability of these PEDOT MSCs is tested in aqueous gel electrolyte which showed a capacitance retention up to 80% over 10,000 cycles with a Coulombic efficiency of 100%. The maximum energy density of solid state ion gel based PEDOT MSCs was found to be 7.7mWh/cm3, which is comparable to the lithium based thin film batteries and superior to the current state-of-the-art carbon and metal oxide based MSCs. Further, the tandem configuration of flexible solid state ion gel based PEDOT MSCs is employed to demonstrate it as a power source for glowing a red light emitting diode. © 2015 Elsevier Ltd.