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

Abstract

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.

Quantifying internal charge transfer and mixed ion-electron transfer in conjugated radical polymers

“…Such asymmetry between anodic and cathodic scans is commonly seen in conjugated polymers. 34,36,37 Notably, the shape of the cathodic current response is largely affected by the radical loading. As the TEMPO loading increased from P3HT-TEMPO-25 to P3HT-TEMPO-100, the cathodic peak became sharper and closer to the current response of homopolymer PTMA.…”

Unusual Internal Electron Transfer in Conjugated Radical Polymers

“…It is noted that the CRP oxidation potential increased slightly with increasing alkyl spacer length, whereas the reduction potential remained constant. This is probably due to the fact that the longer alkyl chains are more electronically insulating, which impedes both electron transfer and ion diffusion . Higher oxidization potentials are required to go from the insulating to the conductive form, but the reverse is not required for the reduction process.…”

Exploring the electrochromic properties of poly(thieno[3,2-b]thiophene)s decorated with electron-deficient side groups

“…8a and b that at low positive or even at negative potentials (−0.5 to +0.2 V) there is a small amount of oxidation states in the neutral P(CNPh-ETTE) and P(Py-ETTE) polymers, which appear as weak polaronic absorptions in the NIR region. This is sometimes observed in EC conducting polymers when they cannot be fully dedoped from the trapped charges 56,57 and this is most likely caused by doping low-oxidation polymer films with atmospheric oxygen. 58 While electropolymerization was done under a nitrogen atmosphere, the SEC experiments in our setup were not performed in situ (the ITO slide with a polymer film was removed from the cell, washed, and then placed into the SEC cell of the spectrophotometer for measurements), so some oxidation/doping by an air might occur.…”