Thermally chargeable supercapacitor using a conjugated conducting polymer: Insight into the mechanism of charge-discharge cycle

Ubiquitous temperature-difference thermally energy, which is typically ignored without use, can be extremely valuable for mobile energy storage devices in environments with large temperature differences. A valuable choice for this low-grade thermally energy recovery has been thermoelectric energy storage or conversion, but small output energy storage necessitates sensitive supercapacitor component such as a suitable electrode material and electrolyte. In this work, a novel conjugated all-conducting polymer is synthesized, namely PDAQ-BC via Buchwald-Hartwig coupling method between 2,6-diaminoanthraquinone (DAQ) and 3,6-dibromo-9-(4-bromophenyl) carbazole (DBC). The PDAQ-BC exhibits specific capacitance of 180.5 F g(-1) at a current of 1 A g(-1) retaining 84% capacitances and about 95% coulombic efficiency upon 5000 cycles at a current density of 5Ag(-1). Furthermore, a thermally chargeable supercapacitor (TCS) assembled by PDAQ-BC electrode and polystyrene sulfonic acid film (PSSH) solid electrolyte, which shows a greatly output potential of 6.67 mV K-1 and stable potential retention over 30 h. With a small temperature gradient of 10.8 and 5.2 degrees C, the TCS produce 72 and 43 mV, respectively. More interestingly, the output potential of TCS is related to temperature gradient and PDAQ-BC electrode, but not to the thickness of the PSSH electrolyte.