Charge Storage in Decyl- and 3,6,9-Trioxadecyl-Substituted Poly(dithieno[3,2-b:2,3-d]pyrrole) Electrodes

Poly(dithieno[3,2-b:2,3-d]pyrrole)s, or poly(DTP)s, are potentially promising electrode materials for electrochemical energy storage (EES) because of their ability to reversibly store charge and achieve relatively high doping levels. Here, we explore charge storage in two different side-chain-substituted poly(DTP)s. Substitution at the nitrogen with alkyl and alkyl ether chains is used to demonstrate the ability to tune electrochemical response through favorable interactions with the electrolyte. PolyDTP electrodes are electropolymerized and analyzed using various electrochemical techniques, spectroscopic measurements including UV-vis and Raman, and electron microscopy. Specific capacities for the poly(DTP)s range between approximately 35 and 70 mAh/g for discharge rates of 1-75 C, corresponding to considerably high doping levels of 0.5-0.9 electrons per repeat unit. After 1000 cycles, the alkyl-substituted polymer retains 75% of its initial capacity while the alkyl ether-substituted polymer only retains 50%. The specific capacitance was as high as 121 F/g. These results suggest that poly(DTP)s could be utilized on their own or in composite electrodes for energy storage.