Efficient Energy Storage by an Asymmetric Poly(3,4-propylenedioxythiophene)//CMK-3 Supercapacitor

Poly(3,4-propylenedioxythiophene) (PProDOT) and ordered mesoporous carbon (CMK-3) as positive and negative electrodes are assembled into an asymmetric supercapacitor (ASC), along with a gel electrolyte containing an ionic lqiuid, for the very first time. The advantages of PProDOT include charge storage by a Faradaic reaction, large electrical conductivity of 11 mS cm–1 in the doped state, robust microstructure that can endure long-term cycling, and ease of scale-up in the form of a thin coating. CMK-3 has the advantage of a porous meso-channelled morphology that enables rapid propagation of electrolyte ions with an effective surface area of 898 m2 g–1, maximizing electrical double layer formation, and a conductivity of ∼12 mS cm–1, which results in a wide operational voltage range of 2 V, an areal specific capacitance (SC) of 294 mF cm–2, an energy density of 0.16 to 0.11 mWh cm–2 at a power density of 0.86 to 3.98 mW cm–2, slow self-discharge rate, low leakage current, and a 98% SC retention after 5000 cycles for the PProDOT//CMK-3 ASC. The enhanced magnitudes of the performance metrics of the PProDOT//CMK-3 ASC in comparison to the inferior performance parameters for the symmetric counterparts (i.e., PProDOT//PProDOT and CMK-3//CMK-3) illustrate the benefits of an asymmetric cell architecture over a symmetric one. Demonstrations of powering a green LED and a digital thermometer with 3-ASCs connected in series show the utilitarian value of this device, for it is not only composed of nontoxic and low-cost components but also can be scaled up easily for the realization of large area supercapacitor devices.